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1.  Daytime Sleep and Parenting Interactions in Infants Born Preterm 
Following a transactional perspective, this longitudinal study assessed concurrent and time-lagged associations between infant daytime sleep behaviors and maternal play interactions within a sample of infants born preterm.
Data were collected from 134 families recruited from 3 Wisconsin NICUs. Multiple methods were used to collect data at infant NICU discharge and when infants were 4, 9, and 24 months postterm, including parent-report infant sleep logs, family sociodemographic assets and a 15 minute video-taped play session.
Within time points, infants who napped more had mothers who were rated as more positive and communicative or less negative during play interactions at 4, 9 and 24 months compared to infants who napped less. Time-lagged findings indicated that infants who took more naps experienced more optimal maternal interactive behaviors later in development than infants who took fewer naps. Additionally, mothers who expressed more negative affect at 4 months or 9 months predicted more infant daytime sleep later in development.
Previous studies document that nighttime parent-child interactions influence nighttime sleep. This study presents the natural extension that daytime sleep influences daytime interactions. The present study draws attention to the understudied area of daytime naps in young children and provides support for the longitudinal bi-directional processes between sleep and parenting interactions.
PMCID: PMC3072039  PMID: 20978444
Preterm; Sleep; Parenting
2.  Nighttime sleep-wake patterns and self-soothing from birth to one year of age: a longitudinal intervention study 
The objectives of this study were to: (1) describe the longitudinal development of sleep-wake patterns of solitary-sleeping infants from 1 to 12 months of age, (2) identify effects on sleep patterns and on self-soothing behaviors of introducing a novel sleep aid, and (3) identify predictive factors of self-soothing at 12 months using a transactional model as a guide.
Eighty infants’ nighttime sleep-wake patterns and associated variables were studied at 5 times across the first year of life using videosomnography and questionnaires.
Sleep-wake state developmental changes, as reported in investigations of infant sleep, were replicated, although a great deal of individual variability in the development of all sleep-related variables was noted. No major effects on sleep or on self-soothing behavior were evident from the introduction of the novel sleep aid. Three variables were identified as significant predictors of self-soothing at 12 months: decreasing amounts of time spent out of crib across the first year, high levels of quiet sleep at birth, and longer parental response times to infant awakenings at 3 months.
These data lend preliminary support for the transactional model and suggest that infant and parental factors interact to influence the development of self-soothing.
PMCID: PMC1201415  PMID: 12236607
Infancy; normal development; parent-child interaction; paediatrics; sleep; temperament; AS: active sleep; AW: wakefulness; BDI: Beck Depression Inventory; GLM: general linear modeling; LSP: longest sleep period; OOC: out of crib; PSOCS: Parenting Sense of Competence Scale; QS: quiet sleep; RSA: representational sleep aid; SC: sham control; SS: self-soothed; TST: total sleep time
3.  Baby Business: a randomised controlled trial of a universal parenting program that aims to prevent early infant sleep and cry problems and associated parental depression 
BMC Pediatrics  2012;12:13.
Infant crying and sleep problems (e.g. frequent night waking, difficulties settling to sleep) each affect up to 30% of infants and often co-exist. They are costly to manage and associated with adverse outcomes including postnatal depression symptoms, early weaning from breast milk, and later child behaviour problems. Preventing such problems could improve these adverse outcomes and reduce costs to families and the health care system. Anticipatory guidance-i.e. providing parents with information about normal infant sleep and cry patterns, ways to encourage self-settling in infants, and ways to develop feeding and settling routines before the onset of problems-could prevent such problems. This paper outlines the protocol for our study which aims to test an anticipatory guidance approach.
750 families from four Local Government Areas in Melbourne, Australia have been randomised to receive the Baby Business program (intervention group) or usual care (control group) offered by health services. The Baby Business program provides parents with information about infant sleep and crying via a DVD and booklet (mailed soon after birth), telephone consultation (at infant age 6-8 weeks) and parent group session (at infant age 12 weeks). All English speaking parents of healthy newborn infants born at > 32 weeks gestation and referred by their maternal and child health nurse at their first post partum home visit (day 7-10 postpartum), are eligible. The primary outcome is parent report of infant night time sleep as a problem at four months of age and secondary outcomes include parent report of infant daytime sleep or crying as a problem, mean duration of infant sleep and crying/24 hours, parental depression symptoms, parent sleep quality and quantity and health service use. Data will be collected at two weeks (baseline), four months and six months of age. An economic evaluation using a cost-consequences approach will, from a societal perspective, compare costs and health outcomes between the intervention and control groups.
To our knowledge this is the first randomised controlled trial of a program which aims to prevent both infant sleeping and crying problems and associated postnatal depression symptoms. If effective, it could offer an important public health prevention approach to these common, distressing problems.
Trial registration number
PMCID: PMC3292472  PMID: 22309617
4.  Sleep and breathing in premature infants at 6 months post-natal age 
BMC Pediatrics  2014;14(1):303.
Poor sleep contributes to the developmental problems seen in preterm infants. We evaluated sleep problems in preterm infants 6 months of post-gestational age using the subjective Brief Infant Sleep Questionnaire (BISQ) and objective sleep tests. We also compared the sleep of premature infants with that of full-term infants.
The study included 68 6-month-old full-term healthy infants and 191 premature infants born at <37 weeks gestation. All parents completed the BISQ-Chinese version and sleep diaries. At the same time, all premature infants were submitted to one night of polysomnography (PSG) in the sleep laboratory and also were set up with an actigraph kept for 7 days. Statistical analyses were performed using correlation coefficients and the t-test with SPSS version 18 to compare questionnaire responses with other subjective and objective measures of sleep.
The sleep problems indicated in the subjective questionnaire for the premature infants, particularly: “the nocturnal sleep duration, number of night awakenings, daytime sleep duration, duration of time with mouth breathing, and loud-noisy breathing” had significant correlations with sleep diaries, actigraphy and PSG results. The BISQ showed that duration of infant’s sleeping on one side, nocturnal sleep duration, being held to fall asleep, number of nighttime awakenings, daytime sleep duration, subjective consideration of sleep problems, loud-noisy breathing, and duration spent crying during the night were significantly different between the premature infants and the term infants. PSG confirmed the presence of a very high percentage (80.6%) of premature infants with AHI > 1 event/hour as indicated by the questionnaire.
Premature infants have more sleep problems than full-term infants, including the known risk of abnormal breathing during sleep, which has been well demonstrated already with the BISQ-Chinese (CBISQ).
Electronic supplementary material
The online version of this article (doi:10.1186/s12887-014-0303-6) contains supplementary material, which is available to authorized users.
PMCID: PMC4272529  PMID: 25510740
Sleep questionnaire; Sleep-disordered breathing; Prematurity; Full-term infant
5.  Sleep and Attachment in Preterm Infants 
Infant mental health journal  2013;34(1):37-46.
Infants born preterm are at elevated risk for social emotional difficulties. However, factors contributing to this risk are largely understudied. Within the present study, we explored infant sleep as a biosocial factor that may play a role in infant social emotional development. Within a prospective longitudinal design, we examined parent-reported sleep patterns and observed parenting quality as predictors of infant-mother attachment in 171 infants born preterm. Using structural equation modeling, we examined main effect and moderator models linking infant sleep patterns and parenting with attachment security. Sleep patterns characterized by more daytime sleep and positive/responsive parenting predicted infant attachment security. Parent-reported nighttime sleep patterns were unrelated to attachment in this sample of infants born preterm. These results indicate that daytime sleep and parenting quality may be important for emerging attachment relationships in infants born preterm.
PMCID: PMC3590002  PMID: 23482430
sleep; attachment; preterm
6.  Maternal Caffeine Consumption and Infant Nighttime Waking: Prospective Cohort Study 
Pediatrics  2012;129(5):860-868.
Coffee and other caffeinated beverages are commonly consumed in pregnancy. In adults, caffeine may interfere with sleep onset and have a dose-response effect similar to those seen during insomnia. In infancy, nighttime waking is a common event. With this study, we aimed to investigate if maternal caffeine consumption during pregnancy and lactation leads to frequent nocturnal awakening among infants at 3 months of age.
All children born in the city of Pelotas, Brazil, during 2004 were enrolled on a cohort study. Mothers were interviewed at delivery and after 3 months to obtain information on caffeine drinking consumption, sociodemographic, reproductive, and behavioral characteristics. Infant sleeping pattern in the previous 15 days was obtained from a subsample. Night waking was defined as an episode of infant arousal that woke the parents during nighttime. Multivariable analysis was performed by using Poisson regression.
The subsample included 885 of the 4231 infants born in 2004. All but 1 mother consumed caffeine in pregnancy. Nearly 20% were heavy consumers (≥300 mg/day) during pregnancy and 14.3% at 3 months postpartum. Prevalence of frequent nighttime awakeners (>3 episodes per night) was 13.8% (95% confidence interval: 11.5%–16.0%). The highest prevalence ratio was observed among breastfed infants from mothers consuming ≥300 mg/day during the whole pregnancy and in the postpartum period (1.65; 95% confidence interval: 0.86–3.17) but at a nonsignificant level.
Caffeine consumption during pregnancy and by nursing mothers seems not to have consequences on sleep of infants at the age of 3 months.
PMCID: PMC3566755  PMID: 22473365
sleep; sleep duration; infant sleeping; night waking; infant; caffeine; coffee
7.  The Intervention Nurses Start Infants Growing on Healthy Trajectories (INSIGHT) study 
BMC Pediatrics  2014;14:184.
Because early life growth has long-lasting metabolic and behavioral consequences, intervention during this period of developmental plasticity may alter long-term obesity risk. While modifiable factors during infancy have been identified, until recently, preventive interventions had not been tested. The Intervention Nurses Starting Infants Growing on Healthy Trajectories (INSIGHT). Study is a longitudinal, randomized, controlled trial evaluating a responsive parenting intervention designed for the primary prevention of obesity. This “parenting” intervention is being compared with a home safety control among first-born infants and their parents. INSIGHT’s central hypothesis is that responsive parenting and specifically responsive feeding promotes self-regulation and shared parent–child responsibility for feeding, reducing subsequent risk for overeating and overweight.
316 first-time mothers and their full-term newborns were enrolled from one maternity ward. Two weeks following delivery, dyads were randomly assigned to the “parenting” or “safety” groups. Subsequently, research nurses conduct study visits for both groups consisting of home visits at infant age 3–4, 16, 28, and 40 weeks, followed by annual clinic-based visits at 1, 2, and 3 years. Both groups receive intervention components framed around four behavior states: Sleeping, Fussy, Alert and Calm, and Drowsy. The main study outcome is BMI z-score at age 3 years; additional outcomes include those related to patterns of infant weight gain, infant sleep hygiene and duration, maternal responsiveness and soothing strategies for infant/toddler distress and fussiness, maternal feeding style and infant dietary content and physical activity. Maternal outcomes related to weight status, diet, mental health, and parenting sense of competence are being collected. Infant temperament will be explored as a moderator of parenting effects, and blood is collected to obtain genetic predictors of weight status. Finally, second-born siblings of INSIGHT participants will be enrolled in an observation-only study to explore parenting differences between siblings, their effect on weight outcomes, and carryover effects of INSIGHT interventions to subsequent siblings.
With increasing evidence suggesting the importance of early life experiences on long-term health trajectories, the INSIGHT trial has the ability to inform future obesity prevention efforts in clinical settings.
Trial registration
NCT01167270. Registered 21 July 2010.
PMCID: PMC4105401  PMID: 25037579
Obesity; Prevention; Infancy; Responsiveness; Home visitation; Feeding; Parenting
8.  The Effects of Iron and/or Zinc Supplementation on Maternal Reports of Sleep in Infants from Nepal and Zanzibar 
There is some evidence that sleep patterns may be affected by iron deficiency anemia but the role of iron in sleep has not been tested in a randomized iron supplementation trial.
We investigated the effect of iron supplementation on maternal reports of sleep in infants in 2 randomized, placebo-controlled trials from Pemba Island, Zanzibar, and Nepal.
In both studies, which had parallel designs and were carried out in years 2002 to 2003, infants received iron–folic acid with or without zinc daily for 12 months, and assessments of development were made every 3 months for the duration of the study. Eight hundred seventy-seven Pemban (12.5 ± 4.0 months old) and 567 Nepali (10.8 ± 4.0 months) infants participated. Maternal reports of sleep patterns (napping frequency and duration, nighttime sleep duration, frequency of night waking) were collected.
Mean Hb concentration was 9.2 ± 1.1 for Pemban and 10.1 ± 1.2 g/dL for Nepali infants. Approximately, one-third of the children were stunted. Supplemental iron was consistently associated with longer night and total sleep duration. The effects of zinc supplementation also included longer sleep duration.
Micronutrient supplementation in infants at high risk for iron deficiency and iron deficiency anemia was related to increased night sleep duration and less night waking.
PMCID: PMC2771202  PMID: 19322104
infants; sleep; iron deficiency anemia; iron supplementation; developing countries
9.  Sleep disorders in children 
BMJ Clinical Evidence  2007;2007:2304.
Sleep disorders may affect 20-30% of young children, and include excessive daytime sleepiness, problems getting to sleep (dysomnias), or undesirable phenomena during sleep (parasomnias), such as sleep terrors, and sleepwalking. Children with physical or learning disabilities are at increased risk of sleep disorders.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatments for dysomnias in children? What are the effects of treatments for parasomnias in children? We searched: Medline, Embase, The Cochrane Library and other important databases up to September 2006 (BMJ Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
We found 14 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
In this systematic review we present information relating to the effectiveness and safety of the following interventions: antihistamines, behavioural therapy plus benzodiazepines, or plus chloral and derivates, exercise, extinction and graduated extinction, light therapy, melatonin, safety/protective interventions for parasomnias, scheduled waking (for parasomnias), sleep hygiene, and sleep restriction.
Key Points
Sleep disorders may affect 20-30% of young children, and include excessive daytime sleepiness, problems getting to sleep (dysomnias), or undesirable phenomena during sleep (parasomnias), such as sleep terrors, and sleepwalking. Children with physical or learning disabilities are at increased risk of sleep disorders. Other risk factors include the child being the first born, having a difficult temperament or having had colic, and increased maternal responsiveness.
There is a paucity of evidence about effective treatments for sleep disorders in children, especially parasomnias, but behavioural interventions may be the best first-line approach.
Extinction and graduated extinction interventions improve settling and reduce night wakes compared with placebo in healthy children, and in children with learning disabilities. Graduated extinction may be less distressing for parents, and therefore may have better compliance.Sleep hygiene interventions may reduce bedtime tantrums in healthy children compared with placebo, with similar effectiveness to graduated extinction.Sleep hygiene plus graduated extinction may reduce bedtime tantrums in children with physical or learning disabilities.We don't know whether combining behavioural therapy with benzodiazepines or with chloral improves sleep or parasomnias.
Melatonin may improve sleep onset and sleep time compared with placebo in healthy children, but we don't know if it is beneficial in children with disabilities, if it improves parasomnias, or what its long-term effects might be. We don't know whether antihistamines, exercise, light therapy, or sleep restriction improve dysomnias or parasomnias in children.We don't know whether safety or protective interventions, scheduled waking, extinction, or sleep hygiene are effective in children with parasomnias.
PMCID: PMC2943792  PMID: 19450298
10.  Symptomatic Dengue Infection during Pregnancy and Infant Outcomes: A Retrospective Cohort Study 
Dengue is a mosquito-borne disease that is common in many tropical and subtropical areas. Dengue infections can occur at any age and time in the lifespan, including during pregnancy. Few large scale studies have been conducted to determine the risk of preterm birth (PTB) and low birthweight (LBW) for infants born to women who had symptomatic dengue infection during pregnancy.
Methodology/Principal Findings
This study is a retrospective cohort study using medical records from 1992–2010 from pregnant women who attended a public regional referral hospital in western French Guiana. Exposed pregnancies were those with laboratory confirmed cases of dengue fever during pregnancy. Each of the 86 exposed infants was matched to the three unexposed births that immediately followed them to form a stratum. Conditional logistic regression was used to analyze these matched strata. Three groups were examined: all infants regardless of gestational age, only infants> = 17 weeks of gestational age and their strata, and only infants> = 22 weeks of age and their strata. Odds ratios were adjusted (aOR) for maternal age, maternal ethnicity, maternal gravidity, interpregnancy interval and maternal anemia. There was an increased risk of PTB among women with symptomatic dengue; (aOR all infants: 3.34 (1.13, 9.89), aOR 17 weeks: 1.89 (0.61, 5.87), aOR 22 weeks: 1.41 (0.39, 5.20)) but this risk was only statistically significant when all infants were examined (p value = 0.03). Adjusted results for LBW were similar, with an increased risk in the exposed group (aOR All infants: 2.23 (1.01, 4.90), aOR 17 weeks: 1.67 (0.71, 3.93), aOR 22 weeks: 1.43 (0.56, 3.70)) which was only statistically significant when all infants were examined (p value = 0.05).
Symptomatic dengue infection during pregnancy may increase the risk of PTB and LBW for infants. More research is needed to confirm these results and to examine the role of dengue fever in miscarriage.
Author Summary
Previous studies have reported that dengue fever during pregnancy may be related to preterm birth and low birthweight among infants. However, few studies have used an appropriate control group to compare the risk of these outcomes for infants whose mothers had dengue fever to infants whose mothers did not. We designed this study to provide information on the amount of risk (odds ratios) and the stability of this risk (confidence intervals) of being born preterm or with low birthweight to a mother with documented dengue infection during the pregnancy. In this study there was an increased risk among pregnant women with symptomatic dengue to deliver infants who are preterm or low birthweight, but both the amount of risk and the stability of this risk were affected by the inclusion or exclusion of miscarriages (infants born before 22 weeks of gestational age) This suggests that women who are pregnant should take extra precautions to avoid dengue infections during pregnancy, since it may cause an early delivery, or the birth of a small infant.
PMCID: PMC4191958  PMID: 25299383
11.  Adverse effects of parental smoking during pregnancy in urban and rural areas 
Parental smoking during pregnancy is associated with lower birthweight and gestational age, as well as with the risks of low birthweight (LBW) and preterm birth. The present study aims to assess the association of parental smoking during pregnancy with birth outcomes in urban and rural areas.
This was a secondary analysis of data collected in the Indonesia Family Life Survey, between 1993 and 2007, the first national prospective longitudinal cohort study in Indonesia. Retrospective data of parental smoking habits, socioeconomic status, pregnancy history and birth outcomes were collected from parents with children aged 0 to 5 years (n = 3789). We assessed the relationships between the amount of parental smoking during pregnancy with birthweight (LBW) and with gestational age (preterm birth).
We found a significant reduction in birthweight to be associated with maternal smoking. Smoking (except for paternal smoking) was associated with a decrease in the gestational age and an increased risk of preterm birth. Different associations were found in urban area, infants born to smoking fathers and both smoking parents (>20 cigarettes/day for both cases) had a significant reduction in birthweight and gestational age as well as an increased risk of LBW and preterm birth.
Residence was found to be an effect modifier of the relation between parental smoking during pregnancy, amount of parental smoking, and birth outcomes on their children. Smoking cessation/reduction and smoking intervention program should be advised and prioritized to the area that is more prone to the adverse birth outcomes.
PMCID: PMC4302514  PMID: 25551278
12.  Sleep disorders in children 
Clinical Evidence  2010;2010:2304.
Sleep disorders may affect between 20% and 30% of young children, and include problems getting to sleep (dyssomnias), or undesirable phenomena during sleep (parasomnias), such as sleep terrors and sleepwalking. Children with physical or learning disabilities are at increased risk of sleep disorders.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatments for dyssomnias in children? What are the effects of treatments for parasomnias in children? We searched: Medline, Embase, The Cochrane Library, and other important databases up to September 2009 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
We found 28 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
In this systematic review we present information relating to the effectiveness and safety of the following interventions: antihistamines; behavioural therapy plus antihistamines, plus benzodiazepines, or plus chloral and derivatives; benzodiazepines alone; exercise; extinction and graduated extinction; 5-hydroxytryptophan; light therapy; melatonin; safety/protective interventions for parasomnias; scheduled waking (for parasomnias); sleep hygiene; and sleep restriction.
Key Points
Sleep disorders may affect between 20% and 30% of young children, and include problems getting to sleep (dyssomnias) or undesirable phenomena during sleep (parasomnias), such as sleep terrors and sleepwalking. Children with physical or learning disabilities are at increased risk of sleep disorders. Other risk factors include the child being the first born, having a difficult temperament or having had colic, and increased maternal responsiveness.
There is a paucity of evidence about effective treatments for sleep disorders in children, especially parasomnias, but behavioural interventions may be the best first-line approach.
Extinction and graduated extinction in otherwise healthy children with dyssomnia may improve sleep quality and settling, and reduce the number of tantrums and wakenings compared with no treatment. Extinction and graduated extinction in children with physical disabilities, learning disabilities, epilepsy, or attention-deficit disorder with dyssomnia may be more effective at improving settling, reducing the frequency and duration of night wakings, and improving parental sleep compared with no treatment; however, we don't know whether it is more effective in improving sleep duration.Graduated extinction may be less distressing for parents, and therefore may have better compliance.
Sleep hygiene for dyssomnia in otherwise healthy children may be more effective in reducing the number and duration of bedtime tantrums compared with placebo, but we don’t know if it is more effective at reducing night wakenings, improving sleep latency, improving total sleep duration, or improving maternal mood. Sleep hygiene and graduated extinction seem to be equally effective at reducing bedtime tantrums in otherwise healthy children with dyssomnia.We don't know whether sleep hygiene for dyssomnia in children with physical disabilities, learning disabilities, epilepsy, or attention-deficit disorder is effective.
Melatonin for dyssomnia in otherwise healthy children may be more effective at improving sleep-onset time, total sleep time, and general health compared with placebo. Evidence of improvements in dyssomnia with melatonin is slightly stronger in children with physical disabilities, learning disabilities, epilepsy, or attention-deficit disorder.
Little is known about the long-term effects of melatonin, and the quality of the product purchased could be variable as melatonin is classified as a food supplement.
Antihistamines for dyssomnia may be more effective than placebo at reducing night wakenings and decreasing sleep latency, but we don’t know if they are more effective at increasing sleep duration. The evidence for antihistamines in dyssomnia comes from only one small, short-term study.
We don’t know whether behavioural therapy plus antihistamines, plus benzodiazepines, or plus chloral and derivatives, exercise, light therapy, or sleep restriction are effective in children with dyssomnia.
We don’t know whether antihistamines, behavioural therapy plus benzodiazepines or plus chloral and derivatives, benzodiazepines, 5-hydroxytryptophan, melatonin, safety/protective interventions, scheduled waking, sleep hygiene, or sleep restriction are effective in children with parasomnia.
PMCID: PMC3217667  PMID: 21418676
13.  First Steps for Mommy and Me: A Pilot Intervention to Improve Nutrition and Physical Activity Behaviors of Postpartum Mothers and Their Infants 
Maternal and child health journal  2011;15(8):1217-1227.
To assess the feasibility of a pediatric primary care based intervention to promote healthful behaviors among 0–6 month old infants and their mothers. We enrolled two intervention practices (60 mother-infant pairs) and one usual care control practice (24 pairs) in a non-randomized controlled trial. We completed visits and interviews with 80 (95%) pairs at birth and 6 months. The intervention included (1) brief focused negotiation by pediatricians, (2) motivational counseling by a health educator, and (3) group parenting workshops. We evaluated the intervention effects on infant feeding, sleep duration, TV viewing, and mothers’ responsiveness to satiety cues. Maternal behavioral targets included postpartum diet, physical activity, TV and sleep. At 6 months, fewer intervention than control infants had been introduced to solid foods (57% vs. 82%; P = 0.04), and intervention infants viewed less TV (mean 1.2 vs. 1.5 h/d; P = 0.07). Compared to control infants, intervention infants had larger increases in their nocturnal sleep duration from baseline to follow up (mean increase 1.9 vs. 1.3 h/d; P = 0.05); larger reductions in settling time (mean reduction −0.70 vs. −0.10 h/d; P = 0.02); and larger reductions in hours/day of nighttime wakefulness (mean reduction −2.9 vs. −1.5 h/d; P = 0.08). There were no differences in breastfeeding, response to satiety cues, or maternal health behaviors. A program of brief focused negotiation by pediatricians, individual coaching by health educators using motivational interviewing, and group parenting workshops tended to improve infant feeding, sleep and media exposure, but had less impact on mothers’ own health-related behaviors.
PMCID: PMC3219434  PMID: 20957514
Postpartum women; Infancy; Nutrition; Physical activity; Obesity prevention
14.  Nighttime Parenting Strategies and Sleep-Related Risks to Infants 
A large social science and public health literature addresses infant sleep safety, with implications for infant mortality in the context of accidental deaths and Sudden Infant Death Syndrome (SIDS). As part of risk reduction campaigns in the USA, parents are encouraged to place infants supine and to alter infant bedding and elements of the sleep environment, and are discouraged from allowing infants to sleep unsupervised, from bed-sharing either at all or under specific circumstances, or from sofa-sharing. These recommendations are based on findings from large-scale epidemiological studies that generate odds ratios or relative risk statistics for various practices; however, detailed behavioural data on nighttime parenting and infant sleep environments are limited. To address this issue, this paper presents and discusses the implications of four case studies based on overnight observations conducted with first-time mothers and their four-month old infants. These case studies were collected at the Mother-Baby Behavioral Sleep Lab at the University of Notre Dame USA between September 2002 and June 2004.Each case study provides a detailed description based on video analysis of sleep-related risks observed while mother-infant dyads spent the night in a sleep lab. The case studies provide examples of mothers engaged in the strategic management of nighttime parenting for whom sleep-related risks to infants arose as a result of these strategies. Although risk reduction guidelines focus on eliminating potentially risky infant sleep practices as if the probability of death from each were equal, the majority of instances in which these occur are unlikely to result in infant mortality. Therefore, we hypothesise that mothers assess potential costs and benefits within margins of risk which are not acknowledged by risk-reduction campaigns. Exploring why mothers might choose to manage sleep and nighttime parenting in ways that appear to increase potential risks to infants may help illuminate how risks occur for individual infants.
PMCID: PMC3505270  PMID: 22818487
infant sleep; sleep-related risks; Sudden Infant Death Syndrome (SIDS); nighttime parenting; USA
15.  The Effects of Napping on Cognitive Function in Preschoolers 
To determine the relationship between napping and cognitive function in preschool-aged children.
Daytime napping, nighttime sleep and cognitive function were assessed in fifty-nine typically developing children ages 3-5 years, who were enrolled in full-time childcare. Participants wore an actigraphy watch for 7 days to measure sleep and napping patterns, and completed neuropsychological testing emphasizing attention, response control, and vocabulary. Parents of participants completed behavior ratings and sleep logs during the study. Sleep/wake cycles were scored with the Sadeh algorithm.
Children who napped more on weekdays were also more likely to nap during weekends. Weekday napping and nighttime sleep were inversely correlated, such that those who napped more slept less at night, while total weekday sleep remained relatively constant. Weekday napping was significantly (negatively) correlated with vocabulary and auditory attention span, and weekday nighttime sleep was positively correlated with vocabulary. Nighttime sleep was also significantly negatively correlated with performance, such that those who slept less at night made more impulsive errors on a computerized go/no-go test.
Daytime napping is actually negatively correlated with neurocognitive function in preschoolers. Nighttime sleep appears to be more critical for development of cognitive performance. Cessation of napping may serve as a developmental milestone of brain maturation. Children who nap less do not appear to be sleep deprived, especially if they compensate with increased nighttime sleep. An alternative explanation is that children who sleep less at night are sleep deprived and require a nap. A randomized trial of nap restriction would be the next step in understanding the relationship between napping and neurocognitive performance.
PMCID: PMC3095909  PMID: 21217402
childhood; attention; sleep; cognition; actigraphy; preschool
16.  Influence of early regulatory problems in infants on their development at 12 months: a longitudinal study in a high-risk sample 
This study examined the extent to which regulatory problems in infants at 4 and 6 months influence childhood development at 12 months. The second aim of the study was to examine the influence maternal distress has on 4-month-old children’s subsequent development as well as gender differences with regard to regulatory problems and development.
153 mother-child dyads enrolled in the family support research project “Nobody slips through the net” constituted the comparison group. These families faced psychosocial risks (e.g. poverty, excessive demands on the mother, and mental health disorders of the mother, measured with the risk screening instrument Heidelberger Belastungsskala - HBS) and maternal stress, determined with the Parental Stress Index (PSI-SF). The children’s developmental levels and possible early regulatory problems were evaluated by means of the Ages and Stages Questionnaires (ASQ) and a German questionnaire assessing problems of excessive crying along with sleeping and feeding difficulties (SFS).
A statistically significant but only low, inverse association between excessive crying, whining and sleep problems at 4 and 6 months and the social development of one-year-olds (accounting for 5% and 8% of the variance respectively) was found. Feeding problems had no effect on development. Although regulatory problems in infants were accompanied by increased maternal stress level, these did not serve as a predictor of the child’s social development at 12 months. One-year-old girls reached a higher level of development in social and fine motor skills. No gender differences were found with regard to regulatory problems, nor any moderating effect of gender on the relation between regulatory problems and level of development.
Our results reinforce existing knowledge pertaining to the transactional association between regulatory problems in infants, maternal distress and dysfunctionality of mother-child interactions. They also provide evidence of a slight but distinct negative influence of crying and sleeping problems on children’s subsequent social development. Easily accessible support services provided by family health visitors (particularly to the so-called “at-risk families”) are strongly recommended to help prevent the broadening of children’s early regulatory problems into other areas of behavior.
PMCID: PMC3854693  PMID: 24119426
Early regulatory problems; Early child development; Mother-child-interaction; Maternal distress; At risk
17.  The Origins of 12-Month Attachment: A Microanalysis of 4-Month Mother-Infant Interaction 
Attachment & human development  2010;12(0):3-141.
A detailed microanalysis of 4-month mother-infant face-to-face communication revealed a fine-grained specification of essential communication processes that predicted 12-month insecure attachment outcomes, particularly resistant and disorganized classifications. An urban community sample of 84 dyads were videotaped at 4 months during a face-to-face interaction, and at 12 months during the Ainsworth Strange Situation. Four-month mother and infant communication modalities of attention, affect, touch, and spatial orientation were coded from split-screen videotape on a 1s time base; mother and infant facial-visual “engagement” variables were constructed. We used contingency measures (multi-level time-series modeling) to examine the dyadic temporal process over time, and specific rates of qualitative features of behavior to examine the content of behavior. Self-contingency (auto-correlation) measured the degree of stability/lability within an individual’s own rhythms of behavior; interactive contingency (lagged cross-correlation) measured adjustments of the individual’s behavior that were correlated with the partner’s previous behavior.
We documented that both self- and interactive contingency, as well as specific qualitative features, of mother and infant behavior were mechanisms of attachment formation by 4 months, distinguishing 12-month insecure, resistant, and disorganized attachment classifications from secure; avoidant were too few to test. All communication modalities made unique contributions. The separate analysis of different communication modalities identified intermodal discrepancies or conflict, both intrapersonal and interpersonal, that characterized insecure dyads. Contrary to dominant theories in the literature on face-to-face interaction, measures of maternal contingent coordination with infant yielded the fewest associations with 12-month attachment, whereas mother and infant self-contingency, and infant contingent coordination with mother, yielded comparable numbers of findings. Rather than the more usual hypothesis that more contingency is “better,” we partially supported our hypothesis that 12-month insecurity is associated with both higher and lower 4-month self- and interactive contingency values than secure, as a function of mother vs. infant and communication modality. Thus, in the origins of attachment security, more contingency is not necessarily better.
A remarkable degree of differentiation was identified in the 4-month patterns of “future” C and D infants, classified as resistant and disorganized, respectively, at 12 months. Only future D infants were emotionally distressed, with simultaneous positive and negative discrepant affect; only their mothers showed difficulty in sharing infant affect, particularly distress, and lowered their contingent coordination with infant facial-visual engagement. This lowered contingent coordination makes it more difficult for infants to come to expect that their emotional/attentional states can influence mothers to coordinate with them and thus compromises the infant’s sense of interactive efficacy. Only future C dyads showed the spatial approach/avoid pattern of “chase and dodge;” only mothers of future D infants showed the spatial intrusion pattern of “looming” into the infant’s face. Both future C and D dyads showed patterns of touch dysregulation. Future C infants inhibited their emotional coordination with mothers’ less affectionate touch, as if tuning it out. Future D dyads showed a dyadic touch dysregulation, in which mothers lowered their coordination with infant touch, while infants had a lowered ability to use their own touch. Both mothers of future C and D infants disturbed the stability of the spatial “frame” of the encounter by transitioning among upward, forward and loom orientations in less predictable ways than mothers of future B infants. Only mothers of future D infants disturbed the attentional “frame” as well, by looking and looking away from the infant’s face in less predictable ways than mothers of future B infants. Only mothers of future D infants showed methods of managing their own state which distanced them from their infants, such as extensive looking away and “closing up” their faces.
The intact interactive contingency of the mother of the future C infant overall safeguards the infant’s interactive agency, and the infant’s expectation that mother will match the direction of infant affective change, sharing infant states. However, we proposed that the future C infant will have difficulty feeling sensed and known by mother during her spatial/tactile intrusions.
The central feature of future D dyads is intrapersonal and interpersonal discordance or conflict in the context of intensely distressed infants. Lowered maternal contingent coordination, and failures of maternal affective correspondence, constitute maternal emotional withdrawal from distressed infants, compromising infant interactive agency and emotional coherence. The level of dysregulation in future D dyads is thus of an entirely different order than that of future C dyads. We proposed that the future D infant represents not being sensed and known by the mother, particularly in states of distress. We proposed that the emerging internal working model of future D infants includes confusion about their own basic emotional organization, about their mothers’ emotional organization, and about their mothers’ response to their distress, setting a trajectory in development which may disturb the fundamental integration of the person.
The findings have rich implications for clinical intervention, with remarkable specificity for different kinds of mother and infant distress. The concepts of heightened and lowered self- and interactive contingency, in different modalities, as well as the specific behavioral qualities identified, provide a more differentiated set of concepts to guide clinical intervention.
PMCID: PMC3763737  PMID: 20390524
18.  Use of Sleep Aids During the First Year of Life 
Pediatrics  2002;109(4):594-601.
In an attempt to foster self-soothing during the night, a novel sleep aid infused with maternal odor was introduced to 4 groups of infants ranging in age from 3 to 12 months. Infants’ use of parent-provided sleep aids also was examined.
Nighttime sleep and waking behaviors were videotaped for 2 consecutive nights on 3 occasions over a 3-month interval. Using all-night video recording, the study examined the infant’s use of a novel sleep aid and parent-provided sleep aids during sleep onset and after nighttime awakenings.
Results indicated that infants of different ages differed in the types of sleep aids used when falling asleep either at the beginning of the night or after awakenings in the middle of the night. More 3-month-olds used their thumbs/fingers/hands, whereas more 6-month-olds used soft objects. The 6-month-olds were most likely to use the novel sleep aid. Almost all of the infants at all 4 ages used some type of object during the night. Intra-individual analyses showed that infants tended to change their pattern of sleep aid use over the 3-month study period.
The data provide evidence that infants during the first year of life use sleep aids frequently and interchangeably rather than a specific favorite object.
PMCID: PMC1351014  PMID: 11927702
19.  Intimate partner violence: associations with low infant birthweight in a South African birth cohort 
Metabolic brain disease  2014;29(2):281-299.
Violence against women is a global public health problem. Exposure to intimate partner violence (IPV) during pregnancy has been associated with a number of adverse maternal and fetal outcomes, including delivery of a low birthweight (LBW) infant. However, there is a paucity of data from low-middle income countries (LMIC). We examined the association between antenatal IPV and subsequent LBW in a South African birth cohort. This study reports data from the Drakenstein Child Lung Health Study (DCLHS), a multidisciplinary birth cohort investigation of the influence of a number of antecedent risk factors on maternal and infant health outcomes over time. Pregnant women seeking antenatal care were recruited at two different primary care clinics in a low income, semi-rural area outside Cape Town, South Africa. Antenatal trauma exposure was assessed using the Childhood Trauma Questionnaire (CTQ) and an IPV assessment tool specifically designed for the purposes of this study. Potential confounding variables including maternal sociodemographics, pregnancy intention, partner support, biomedical and mental illness, substance use and psychosocial risk were also assessed. Bivariate and multiple regression analyses were performed to determine the association between IPV during pregnancy and delivery of an infant with LBW and/or low weight-for-age z (WAZ) scores. The final study sample comprised 263 mother-infant dyads. In multiple regression analyses, the model run was significant [r2=0.14 (adjusted r2=0.11, F(8, 212) = 4.16, p=0.0001]. Exposure to physical IPV occurring during the past year was found to be significantly associated with LBW [t=−2.04, p=0.0429] when controlling for study site (clinic), maternal height, ethnicity, socioeconomic status, substance use and childhood trauma. A significant association with decreased WAZ scores was not demonstrated. Exposure of pregnant women to IPV may impact newborn health. Further research is needed in this field to assess the relevant underlying mechanisms, to inform public health policies and to develop appropriate trauma IPV interventions for LMIC settings.
PMCID: PMC4300125  PMID: 24729207
Intimate partner violence; Trauma; Pregnancy; Low birth weight; South Africa
20.  Bottle feeding and the sudden infant death syndrome. 
BMJ : British Medical Journal  1995;310(6972):88-90.
OBJECTIVE--To determine whether the risk of the sudden infant death syndrome is increased in bottle fed babies. DESIGN--Population based case-control study matching for age and time. SUBJECTS--All babies aged 1 week to 1 year dying of sudden infant death syndrome during November 1987 to April 1989 or February 1990 to June 1991 and two live controls. SETTING--Avon and north Somerset. MAIN OUTCOME MEASURES--Breast or bottle feeding, sleeping position, maternal smoking, parental employment, and length of gestation. RESULTS--Compared with being fully breast fed, the crude odds ratio for sudden infant death in fully bottle fed babies was 3.1 and for mixed breast and bottle fed babies 1.5. These odds ratios fell to 1.8 (95% confidence interval 0.7 to 4.8) and 1.2 (0.5 to 2.7) respectively after maternal smoking, parental employment, preterm gestation, and sleeping position had been adjusted for. Sleeping position partly masked the effect of being bottle fed on sudden infant death as breast fed babies were more likely to have slept prone than bottle fed babies. CONCLUSIONS--Bottle feeding is not a significant independent risk factor for the sudden infant death syndrome. Patterns of maternal smoking, preterm gestation, and parental employment status account for most of the apparent association with bottle feeding.
PMCID: PMC2548486  PMID: 7833732
21.  Trends and Factors Associated with Infant Sleeping Position: The National Infant Sleep Position Study 1993-2007 
SIDS remains the leading cause of postneonatal death in the US. To decrease risk, infants should be placed supine for sleep.
Determine trends and factors associated with choice of infant sleeping position.
National Infant Sleep Position Study (NISP): Annual nationally representative telephone surveys.
48 contiguous states of the United States.
Nighttime caregivers of infants born within the last 7 months between 1993 and 2007. Approximately 1000 interviews each year.
Main Outcome Measure:
Infant usually placed to sleep in the supine position.
For the 15-year period, supine sleep increased (p<0.0001) and prone sleep decreased (p<0.0001) for all infants with no significant difference in trend by race. Since 2001 a plateau has been reached for all races.
Factors associated with increase supine sleep between 1993-2007 included: time, maternal race other than Black, higher maternal education, not living in Southern States, first-born infant, and full-term infant. Impact of these variables was reduced when variables related to maternal concerns about infant comfort, infant choking and advice received from doctors were taken into account.
Between 2003 and 2007, choice of infant sleep position could be explained almost entirely by caregiver concern about comfort, choking and advice. Race no longer was a significant predictor of supine sleep.
Since 2001 supine sleep has reached a plateau, and there continue to be racial disparities in both sleep practice and death rates. There have been changes in factors associated with sleep position and maternal attitudes about issues such as comfort and choking concerns may account for much of the racial disparity in practice. To decrease SIDS, we must ensure that public health measures reach the populations at risk and include messages that address concerns about infant comfort or choking in the supine position.
PMCID: PMC2898125  PMID: 19996049
22.  Setting research priorities to reduce global mortality from preterm birth and low birth weight by 2015 
Journal of Global Health  2012;2(1):010403.
This paper aims to identify health research priorities that could improve the rate of progress in reducing global neonatal mortality from preterm birth and low birth weight (PB/LBW), as set out in the UN's Millennium Development Goal 4.
We applied the Child Health and Nutrition Research Initiative (CHNRI) methodology for setting priorities in health research investments. In the process coordinated by the World Health Organization in 2007–2008, 21 researchers with interest in child, maternal and newborn health suggested 82 research ideas that spanned across the broad spectrum of epidemiological research, health policy and systems research, improvement of existing interventions and development of new interventions. The 82 research questions were then assessed for answerability, effectiveness, deliverability, maximum potential for mortality reduction and the effect on equity using the CHNRI method.
The top 10 identified research priorities were dominated by health systems and policy research questions (eg, identification of LBW infants born at home within 24–48 hours of birth for additional care; approaches to improve quality of care of LBW infants in health facilities; identification of barriers to optimal home care practices including care seeking; and approaches to increase the use of antenatal corticosteriods in preterm labor and to improve access to hospital care for LBW infants). These were followed by priorities for improvement of the existing interventions (eg, early initiation of breastfeeding, including feeding mode and techniques for those unable to suckle directly from the breast; improved cord care, such as chlorhexidine application; and alternative methods to Kangaroo Mother Care (KMC) to keep LBW infants warm in community settings). The highest-ranked epidemiological question suggested improving criteria for identifying LBW infants who need to be cared for in a hospital. Among the new interventions, the greatest support was shown for the development of new simple and effective interventions for providing thermal care to LBW infants, if KMC is not acceptable to the mother.
The context for this exercise was set within the MDG4, requiring an urgent and rapid progress in mortality reduction from low birth weight, rather than identifying long-term strategic solutions of the greatest potential. In a short-term context, the health policy and systems research to improve access and coverage by the existing interventions, coupled with further research to improve effectiveness, deliverability and acceptance of existing interventions, and epidemiological research to address the key gaps in knowledge, were all highlighted as research priorities.
PMCID: PMC3484758  PMID: 23198132
23.  The Contribution of Infant, Maternal, and Family Conditions to Maternal Feeding Competencies 
Because little is known about the role of family problem-solving processes in the development of mothers’ competencies in feeding a very low birth-weight (VLBW) infant, we explored the contribution made by the competence in negotiating displayed by a mother and family member as they jointly problem solve infant-care issues. The infant’s neonatal biomedical condition, maternal depressive symptoms, and family poverty status may also contribute to feeding competencies.
A sample of 41 mothers of VLBW infants from 2 longitudinal studies who were observed during feeding at 1 and 8 months infant postterm age, with a family member of their choosing, participated in a dyadic problem-solving exercise. We assessed maternal feeding competencies with the Parent–Child Early Relational Assessment (Clark, 1997) and dyadic negotiating competence using an observational scale from the Iowa Family Interaction Rating Scales (Melby & Conger, 2001). We classified infant condition through medical record audit. Maternal depressive symptoms were assessed with the Center for Epidemiologic Studies-Depression (CES-D) Scale (L. S. Radloff, 1977), and family poverty status was determined through the mother’s report of family income.
Mothers’ feeding competencies, structured into 2 factors, Parental Positive Affective Involvement, Sensitivity, and Responsiveness (PPAISR) and Parental Negative Affect and Behavior (PNAB, scored in the direction of low negativity) were stable from 1 to 8 months, accounting for the entire set of predictor variables. Neonatal biomedical condition had no effect on either PPAISR or PNAB; depressive symptoms were negatively associated with PNAB at 8 months; poverty status negatively predicted both PPAISR and PNAB at 1 and 8 months; and negotiating competence of the mother–family member dyad was positively associated with PNAB at 1 month.
Evidence that family poverty status and dyadic negotiating competence were both associated with maternal feeding competencies supports inclusion of these family-level variables in a model of feeding competencies. A mother’s negotiating competence with another family member who takes a responsible role in infant care may support maternal feeding competencies during a VLBW infant’s early weeks when parenting patterns are forming.
PMCID: PMC3227219  PMID: 22140356
24.  Eye of the beholder? Maternal mental health and the quality of infant sleep 
Transactional models of parenting and infant sleep call attention to bidirectional associations among parenting, the biosocial environment, and infant sleep behaviors. Although night waking and bedtime fussing are normative during infancy and early childhood, they can be challenging for parents. The current study, conducted in the United States between 2003 and 2009, examined concurrent and longitudinal associations between maternal mental health and infant sleep during the first year. Concurrent associations at 6 and 12 months and longitudinal associations from 6 to 12 months were studied in a non-clinic referred sample of 171 economically and culturally diverse families. Mothers with poorer mental health reported that their infants had more night waking and bedtime distress and were more bothered by these sleep issues. Associations between infant sleep and maternal mental health were moderated by culture (Hispanic/Asian vs. other) and by stressors that included high parenting stress, more stressful life events, and low family income. Individual differences in maternal well-being may color mothers’ interpretations of infants’ sleep behaviors. It may be prudent to intervene to support maternal mental health when infants are referred for sleep problems.
PMCID: PMC3540198  PMID: 22858167
night waking; infancy; sleep problems; depressive symptoms; anxiety; United States; mothers; ethnicity
25.  US Birth Weight/Gestational Age-Specific Neonatal Mortality: 1995–1997 Rates for Whites, Hispanics, and Blacks 
Pediatrics  2003;111(1):e61-e66.
In recent years, gains in neonatal survival have been most evident among very low birth weight, preterm, and low birth weight (LBW) infants. Most of the improvement in neonatal survival since the early 1980s seems to be the consequence of decreasing birth weight-specific mortality rates, which occurred during a period of increasing preterm and LBW rates. Although the decline in neonatal mortality has been widely publicized in the United States, research suggests that clinicians may still underestimate the chances of survival of an infant who is born too early or too small and may overestimate the eventuality of serious disability. So that clinicians may have current and needed ethnic- and race-specific estimates of the “chances” of early survival for newborn infants, we examined birth weight/gestational age-specific neonatal mortality rates for the 3 largest ethnic/racial groups in the United States: non-Hispanic whites, Hispanics, and non-Hispanic blacks. Marked racial variation in birth weight and gestational age-specific mortality has long been recognized, and growing concerns have been raised about ongoing and increasing racial disparities in pregnancy outcomes. Our purpose for this investigation was to provide an up-to-date national reference for birth weight/gestational age-specific neonatal mortality rates for use by clinicians in care decision making and discussions with parents.
The National Center for Health Statistics linked live birth-infant death cohort files for 1995–1997 were used for this study. Singleton live births to US resident mothers with a reported maternal ethnicity/race of non-Hispanic white, non-Hispanic black, or Hispanic (n = 10 610 715) were selected for analysis. Birth weight/gestational age-specific neonatal mortality rates were calculated using 250 g/2-week intervals for each ethnic/racial group.
The overall neonatal mortality rates for whites, Hispanics, and blacks were 3.24, 3.45, and 8.16 neonatal deaths per 1000 live births, and the proportion of births <28 weeks was 0.35%, 0.45%, and 1.39%, respectively. Newborns who weighed <1500 g comprised <2.5% of all births in each racial/ethnic group but accounted for >50% of neonatal deaths. For whites, Hispanics, and blacks, >50% of newborns 24 to 25 weeks of gestational age survived. For most combinations of birth weights <3500 g and gestational ages of <37 weeks, the neonatal mortality rate was lowest among blacks, compared with whites or Hispanics. At these same gestational age/birth weight combinations, Hispanics have slightly lower mortality rates than whites. For combinations of birth weights >3500 g and gestational ages of 37 to 41 weeks, Hispanics had the lowest neonatal mortality rate. In these birth weight/gestational age combinations, where approximately two thirds of births occur, blacks had the highest neonatal mortality rate.
Compared with earlier reports, these data suggest that a substantial improvement in birth weight/gestational age-specific neonatal mortality has occurred in the United States. Regardless of ethnicity/race, the risk of a neonatal death does not exceed 50% (the suggested definition for the limit of viability), except for birth weights below 500 g and gestational ages <24 weeks. Notwithstanding, ethnic/racial variations in neonatal mortality rates continue to persist, both in overall rates and within birth weight/gestational age categories. Blacks continue to have higher proportions for preterm and LBW births, compared with either whites or Hispanics. At the same time, blacks experience lower risks of neonatal mortality for preterm and LBW infants, while having higher risks of mortality among term, postterm, normal birth weight, and macrosomic births.
PMCID: PMC1382183  PMID: 12509596
VLBW, very low birth weight; LBW, low birth weight; BG-NMR, birth weight/gestational age-specific neonatal mortality rate; NCHS, National Center for Health Statistics; LMP, last normal menstrual period

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