Survey response rates have been declining over the past decade. The more widespread use of the Internet and Web-based technologies among potential health survey participants suggests that Web-based questionnaires may be an alternative to paper questionnaires in future epidemiological studies.
To compare response rates in a population of parents by using 4 different modes of data collection for a questionnaire survey of which 1 involved a nonmonetary incentive.
A random sample of 3148 parents of Danish children aged 2-17 years were invited to participate in the Danish part of the NordChild 2011 survey on their children’s health and welfare. NordChild was conducted in 1984 and 1996 in collaboration with Finland, Iceland, Norway, and Sweden using mailed paper questionnaires only. In 2011, all countries used conventional paper versions only except Denmark where the parents were randomized into 4 groups: (1) 789 received a paper questionnaire only (paper), (2) 786 received the paper questionnaire and a log-in code to the Web-based questionnaire (paper/Web), (3) 787 received a log-in code to the Web-based questionnaire (Web), and (4) 786 received log-in details to the Web-based questionnaire and were given an incentive consisting of a chance to win a tablet computer (Web/tablet). In connection with the first reminder, the nonresponders in the paper, paper/Web, and Web groups were also present with the opportunity to win a tablet computer as a means of motivation. Descriptive analysis was performed using chi-square tests. Odds ratios were used to estimate differences in response rates between the 4 modes.
In 2011, 1704 of 3148 (54.13%) respondents answered the Danish questionnaire. The highest response rate was with the paper mode (n=443, 56.2%). The other groups had similar response rates: paper/Web (n=422, 53.7%), Web (n=420, 53.4%), and Web/tablet (n=419, 53.3%) modes. Compared to the paper mode, the odds for response rate in the paper/Web decreased by 9% (OR 0.91, 95% CI 0.74-1.10) and by 11% (OR 0.89, 95% CI 0.73-1.09) in the Web and Web/tablet modes. The total number of responders for NordChild declined from 10,291 of 15,339 (67.09%) in 1984 and 10,667 of 15,254 (69.93%) in 1996 to 7805 of 15,945 (48.95%) in 2011 with similar declines in all 5 Nordic countries.
Web-based questionnaires could replace traditional paper questionnaires with minor effects on response rates and lower costs. The increasing effect on the response rate on participants replying for a nonmonetary incentive could only be estimated within the 2 Web-based questionnaire modes before the first reminder. Alternative platforms to reach higher participation rates in population surveys should reflect the development of electronic devices and the ways in which the population primarily accesses the Internet.
mixed-mode survey; patient participation rate; Web-based; paper; questionnaires; nonmonetary incentive
To evaluate general practitioners’ (GPs’) assessment of potential overweight among children attending the five-year preventive child health examination (PCHE) by comparing their assessment of the children's weight-for-stature with overweight defined by body mass index (BMI) according to paediatric standard definitions.
A cross-sectional survey. Data were obtained from a questionnaire survey of children's health in general and their growth in particular.
The five-year preventive child health examination (PCHE) in general practice in the Central Denmark Region.
Children attending the five-year PCHE in general practice, regardless of their weight status.
Main outcome measures
Paediatric standard definitions for childhood overweight based on BMI were used as the gold standard for categorizing weight-for-stature. Identification of overweight was analysed with regard to sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the GPs’ assessment of weight-for-stature.
A total of 165 GPs conducted 1138 PCHEs. GPs assessed that 171 children had a weight-for-stature above normal. Use of the Danish Standards (DS), i.e. the Danish national growth charts for BMI, as the gold standard yielded a sensitivity of 70.1% (95% CI 62.0–77.3) and a specificity of 92.4% (95% CI 90.6–93.9). The sensitivity was influenced by the GPs’ use of BMI and the presence of previous notes regarding abnormal weight development.
At the five-year PCHE almost one-third of overweight children were assessed to be normal weight by GPs. Use of BMI and presence of notes on abnormal weight in medical records were positively associated with a higher identification. Hence, utilization of medical record data and BMI charts may refine GPs’ assessment of childhood overweight.
Assessment; children; Denmark; general practice; overweight; preventive child health examination
The etiology of type-2 diabetes is only partly known, and a possible role of prenatal stress in programming offspring for insulin resistance has been suggested by animal models. Previously, we found an association between prenatal stress and type-1 diabetes. Here we examine the association between prenatal exposure to maternal bereavement during preconception and pregnancy and development of type-2 diabetes in the off-spring.
We utilized data from the Danish Civil Registration System to identify singleton births in Denmark born January 1st 1979 through December 31st 2008 (N = 1,878,246), and linked them to their parents, grandparents, and siblings. We categorized children as exposed to bereavement during prenatal life if their mothers lost an elder child, husband or parent during the period from one year before conception to the child’s birth. We identified 45,302 children exposed to maternal bereavement; the remaining children were included in the unexposed cohort. The outcome of interest was diagnosis of type-2 diabetes. We estimated incidence rate ratios (IRRs) from birth using log-linear poisson regression models and used person-years as the offset variable. All models were adjusted for maternal residence, income, education, marital status, sibling order, calendar year, sex, and parents’ history of diabetes at the time of pregnancy.
We found children exposed to bereavement during their prenatal life were more likely to have a type-2 diabetes diagnosis later in life (aIRR: 1.31, 1.01–1.69). These findings were most pronounced when bereavement was caused by death of an elder child (aIRR: 1.51, 0.94–2.44). Results also indicated the second trimester of pregnancy to be the most sensitive period of bereavement exposure (aIRR:2.08, 1.15–3.76).
Our data suggests that fetal exposure to maternal bereavement during preconception and the prenatal period may increase the risk for developing type-2 diabetes in childhood and young adulthood.
The aetiology of childhood cancer remains largely unknown but recent research indicates that uterine environment plays an important role. We aimed to examine the association between the Apgar score at 5 min after birth and the risk of childhood cancer.
Nationwide population-based cohort study.
Nationwide register data in Denmark and Sweden.
All live-born singletons born in Denmark from 1978 to 2006 (N=1 771 615) and in Sweden from 1973 to 2006 (N=3 319 573). Children were followed up from birth to 14 years of age.
Main outcome measures
Rates and HRs for all childhood cancers and for specific childhood cancers.
A total of 8087 children received a cancer diagnosis (1.6 per 1000). Compared to children with a 5-min Apgar score of 9–10, children with a score of 0–5 had a 46% higher risk of cancer (adjusted HR 1.46, 95% CI 1.15 to 1.89). The potential effect of low Apgar score on overall cancer risk was mostly confined to children diagnosed before 6 months of age. Children with an Apgar score of 0–5 had higher risks for several specific childhood cancers including Wilms’ tumour (HR 4.33, 95% CI 2.42 to 7.73).
A low 5 min Apgar score was associated with a higher risk of childhood cancers diagnosed shortly after birth. Our data suggest that environmental factors operating before or during delivery may play a role on the development of several specific childhood cancers.
Oncology; Epidemiology; Paediatric oncology; Preventive Medicine
The Strength and Difficulties Questionnaire (SDQ) is a brief behavioural five factor instrument developed to assess emotional and behavioural problems in children and adolescents. The aim of the current study was to evaluate the psychometric properties for parent and teacher ratings in the Danish version of SDQ for different age groups of boys and girls.
The Danish versions of the SDQ were distributed to a total of 71,840 parent and teacher raters of 5-, 7- and 10- to 12-year-old children included in four large scale Danish cohorts. The internal reliability was assessed and exploratory factor analyses were carried out to replicate the originally proposed five factor structure. Mean scores and percentiles were examined in order to differentiate between low, medium and high levels of emotional and behavioural difficulties.
The original five factor structure could be substantially confirmed. The Conduct items however did not solely load on the proposed Conduct scale and the Conduct scale was further contaminated by non-conduct items. Positively worded items tended to load on the Prosocial scale. This was more so the case for teachers than for parents. Parent and teacher means and percentiles were found to be lower compared to British figures but similar to or only slightly lower than those found in the other Nordic countries. The percentiles for girls were generally lower than for boys, markedly so for the teacher hyperactivity ratings.
The study supports the usefulness of the SDQ as a screening tool for boys and girls across age groups and raters in the general Danish population.
Children born after in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) have been reported to have a higher risk of cerebral palsy (CP), perhaps due to the higher frequency of preterm birth, multiple births or vanishing embryo in the pregnancies. However, it has been suggested that the underlying infertility may be part of the pathway. In this study, we examined whether untreated subfecundity (measured by time to pregnancy) or infertility treatment was associated with an increased risk of CP in the offspring.
Using the Danish National Birth Cohort (1997–2003), we compared children born after 0–2 months of waiting time to pregnancy (n = 35 848) with those born after a time to pregnancy of 3–5 months (n = 15 361), 6–12 months (n = 11 528) and >12 months (n = 7387), as well as those born after IVF/ICSI (n = 3617), ovulation induction with or without intrauterine insemination (n = 3000), and unplanned pregnancies (n = 13 462). CP cases were identified through the Danish CP Register.
In total, 165 (0.18%) children were diagnosed with CP in the entire cohort. We found no significant association between time to pregnancy and the risk of CP in children conceived spontaneously. Children born after IVF/ICSI had an increased risk of CP, even after adjustment for preterm birth and multiplicity (hazard ratio 2.30, 95% confidence interval 1.12–4.73).
Subfecundity per se did not appear to be associated with the risk of CP in children, whereas being born after IVF/ICSI conferred an increased risk.
cerebral palsy; infertility; infertility treatment; time to pregnancy; Danish National Birth Cohort
A number of studies have examined the effects of prenatal exposure to stress on birth outcomes but few have specifically focused on psychosocial job strain. In the present protocol, we aim to examine if work characterised by high demands and low control, during pregnancy, is associated with the risk of giving birth to a child born preterm or small for gestational age.
Methods and design
We will use the Danish National Birth Cohort where 100.000 children are included at baseline. In the present study 49,340 pregnancies will be included. Multinomial logistic regression will be applied to estimate odds ratios for the outcomes: preterm; full term but small for gestational age; full term but large for gestational age, as a function of job-strain (high strain, active and passive versus low strain). In the analysis we control for maternal age, Body Mass Index, parity, exercise, smoking, alcohol use, coffee consumption, type of work (manual versus non-manual), maternal serious disease and parents' heights as well as gestational age at interview.
The prospective nature of the design and the high number of participants strengthen the study. The large statistical power allows for interpretable results regardless of whether or not the hypotheses are confirmed. This is, however, not a controlled study since all kinds of 'natural' interventions takes place throughout pregnancy (e.g. work absence, medical treatment and job-redesign). The analysis will be performed from a public health perspective. From this perspective, we are not primarily interested in the effect of job strain per se but if there is residual effect of job strain after naturally occurring preventive measures have been taken.
To estimate the prevalence of the ADHD phenotype based on parent and teacher reports in a general population sample of 7- to 9-year-old Norwegian children and evaluate the effect of parent attrition, gender and informant on the prevalence estimate.
The population consisted of all children (N = 9,430) attending 2nd–4th grade in the City of Bergen, Norway. The 18 symptoms of ADHD corresponding to the SNAP-IV and DSM-IV were included in the Bergen Child Study questionnaire to teachers and parents. Teacher information was available for 9,137 children (97%) and information from both informants was available for the 6,237 children (66%) whose parents agreed to participate in the study.
The prevalence of the ADHD phenotype based on the combination of parent and teacher reports was 5.2% among participants. Teacher ratings of non-participants had a doubled rate of ADHD high scorers with an OR of 2.1 (95% CI, 1.9–2.4). The non-participant ADHD high scorers had more inattentive and fewer hyperactive/impulsive symptoms as compared to participating ADHD high scorers. Teachers reported high scores of hyperactivity/impulsivity and the combined symptom constellation much more frequently in boys than girls, while the difference between genders was less marked according to parent reports.
The ADHD phenotype was twice as prevalent among non-participants as among participants. Reported prevalences in population studies are therefore likely to be underestimates, if such attrition bias is not accounted for. Choice of informant, criteria for symptom count, definitions of subtypes and gender differences influence the prevalence estimates of the ADHD phenotype.
Attention-deficit/hyperactivity disorder; Child psychiatry; Epidemiology; Attrition; Gender
It has previously been reported that children born after infertility treatment had a slight delay in early motor milestones. In this study, we examined whether children of infertile couples with or without infertility treatment had a higher risk of developmental coordination disorder (DCD).
We used data on parental infertility and DCD among 23 167 singletons from the Danish National Birth Cohort (1996–2002). Data on time to pregnancy (TTP) and infertility treatment were collected early in pregnancy. Data on DCD in children were collected using the Developmental Coordination Disorder Questionnaire, filled in by the mothers during follow-up when the children were 7 years old. We used the recommended cut-off for the age group to classify children.
Compared with children born of fertile couples, children conceived after a waiting TTP of longer than 12 months had a slightly higher risk of DCD [odds ratio (OR) 1.35, 95% confidence interval (CI) 1.03–1.77], but the estimated OR was not significant in children born after infertility treatment (OR 1.19, 95% CI 0.86–1.66). None of the individual treatment procedures was significantly associated with a higher risk of DCD. Children of parents who had not planned their pregnancy showed no elevated risk.
Our findings are overall reassuring, although it is possible that low fecundity may be associated with a modestly increased risk of DCD.
assisted reproduction technologies; developmental coordination disorder; infertility
Mixed-handedness, which may reflect atypical brain laterality, has been linked to a number of medical conditions as well as prenatal stress.
The aim of the study was to examine whether infertility or infertility treatment was associated with an increased risk of mixed-handedness in children.
Study design, subjects and outcome measures
We used data from three population-based birth cohorts in Denmark: the Aalborg-Odense Birth Cohort (1984-1987), the Aarhus Birth Cohort (1990-1992) and the Danish National Birth Cohort (1996-2002) (N=7728, 5720 and 29486, respectively). Data on time to pregnancy and infertility treatment was collected during pregnancy. Handedness was reported in a follow-up questionnaire when the children were at least 7 years old. Children were categorized as mixed-handed if the mothers reported that they used both hands equally.
Children born after infertility treatment, particularly intrauterine insemination, had a higher risk of being mixed-handed compared to children of fertile couples with a time to pregnancy ≤12 months (odds ratio 1.41, 95% confidence interval 1.09-1.82). Children of couples with unplanned pregnancies, particularly after an oral contraceptives failure, were also more likely to be mixed-handed. There was no association between a long waiting time to pregnancy and mixed-handedness in children.
Children born after infertility treatment, particularly intrauterine insemination, and children exposed to oral contraceptives during early gestation may have a higher risk of being mixed-handed.
Infertility; Infertility treatment; Mixed-handedness; Oral contraceptives; Time to pregnancy
It has been suggested that prenatal stress contributes to the risk of obesity later in life. In a population–based cohort study, we examined whether prenatal stress related to maternal bereavement during pregnancy was associated with the risk of overweight in offspring during school age.
We followed 65,212 children born in Denmark from 1970–1989 who underwent health examinations from 7 to 13 years of age in public or private schools in Copenhagen. We identified 459 children as exposed to prenatal stress, defined by being born to mothers who were bereaved by death of a close family member from one year before pregnancy until birth of the child. We compared the prevalence of overweight between the exposed and the unexposed. Body mass index (BMI) values and prevalence of overweight were higher in the exposed children, but not significantly so until from 10 years of age and onwards, as compared with the unexposed children. For example, the adjusted odds ratio (OR) for overweight was 1.68 (95% confidence interval [CI] 1.08–2.61) at 12 years of age and 1.63 (95% CI 1.00–2.61) at 13 years of age. The highest ORs were observed when the death occurred in the period from 6 to 0 month before pregnancy (OR 3.31, 95% CI 1.71–6.42 at age 12, and OR 2.31, 95% CI 1.08–4.97 at age 13).
Our results suggest that severe pre-pregnancy stress is associated with an increased risk of overweight in the offspring in later childhood.
To assess the risk of developing Type-1 diabetes among children who were exposed to maternal bereavement during the prenatal or 1-year preconception period.
We identified N = 1,548,746 singleton births born in Denmark between January 1st 1979 through December 31st 2004, and their next of kin. Altogether, 39,857 children were exposed to bereavement during their prenatal life. The main outcome of interest was hospitalization for type-1 diabetes (ICD 8: 249; ICD 10: E10).
We found the strongest association for type-1 diabetes among children exposed to traumatic father or sibling deaths (aIRR: 2.03, 1.22–3.38); the association was mainly seen for girls (aIRR: 2.91, 1.61–5.26).
We found evidence to suggest that female fetuses exposed to severe prenatal stress are at increased risk for developing type-1 diabetes.
Babies born of infertile couples, regardless of treatment, have a higher risk of preterm birth and low birthweight, conditions associated with delayed development. We examined developmental milestones in singletons as a function of parental infertility [time to pregnancy (TTP) >12 months] and infertility treatment. From the Danish National Birth Cohort (1997–2003), we identified 37,897 singletons born of fertile couples (TTP ≤12 months), 4351 born of infertile couples conceiving naturally (TTP >12 months), and 3309 born after infertility treatment. When the children were about 18 months old, mothers reported 12 developmental milestones by responding to structured questions. We defined a failure to achieve the assessed milestone or the minimal numbers of milestones in a summary (motor, or cognitive/language skills) as delay. Naturally conceived children born of infertile couples had a pattern of psychomotor development similar to that of children born of fertile couples, but increasing TTP correlated with a modest delay. When the analysis was restricted to infertile couples (treated and untreated), children born after treatment showed a slight delay in cognitive/language development (odds ratio 1.24, [95% confidence interval 1.01, 1.53] for not meeting at least three out of six cognitive/language milestones); children born after intracytoplasmic sperm injection (ICSI) had the highest estimated relative risk of delay for most milestones, especially motor milestones. These results suggest that a long TTP may be associated with a modest developmental delay. Infertility treatment, especially ICSI, may be associated with a slight delay for some of these early milestones.
child development; infertility; assisted reproductive techniques
The reproductive health of children born of infertile couples may be affected by infertility treatment or factors associated with infertility. We examined sexual maturation in children of parents with infertility.
We used data from a follow-up of 3382 girls and 2810 boys born between 1984 and 1987 in the Aalborg–Odense Birth Cohort. We had mothers’ report of time to pregnancy (TTP) and infertility treatment (at the time, mostly hormonal) from the pregnancy questionnaire administered in 1984–1987, and the children’s report of their own sexual maturation from the follow-up questionnaire administered in 2005, when they were between 18 and 21 years old. Many reported age only in year when they had the events related to sexual maturation, and for each event, we imputed the month based on the median month at each year of age among those reporting both years and months.
In girls, the mean age at menarche was 13.3 years and, in boys, the mean age at appearance of acne, voice break, regular shaving and first nocturnal emission were 14.5, 14.5, 17.2 and 14.7 years, respectively. We saw no significant differences in age at these events among children born of either fertile (with TTP of 0–12 months and no treatment), untreated infertile (with TTP of more than 12 months and no treatment) or treated infertile couples (with a history of examination or treatment for infertility).
Our data suggest no significant association between parental infertility or hormonal treatment and timing of sexual maturation in the offspring.
infertility; infertility treatment; puberty; time to pregnancy
Non-right handedness, particularly mixed-handedness, has been associated with a number of medical conditions. We examined whether handedness was associated with fecundity, measured by time to pregnancy.
We used data on parental handedness and time to pregnancy from two regional birth cohorts in Denmark: the Aalborg-Odense Birth Cohort (1984–1987) and the Aarhus Birth Cohort (1990–1992) (N=5808 and 3426, respectively). We applied discrete-time survival analysis to assess fecundity in relation to handedness.
In both cohorts, we saw a slightly lower fecundity in individuals who reported being mixed-handed. Left handedness was not significantly associated with fecundity.
Our data showed a modest association between mixed-handedness and subfecundity, which suggests that these traits may share a common prenatal etiology.
handedness; fecundity; time to pregnancy
To examine the association between infertility, with or without treatment, and fetal growth, as well as perinatal and infant mortality.
From the Danish National Birth Cohort (1997–2003), we identified 51,041 singletons born of fertile couples (time to pregnancy ≤12 months), 5787 born of infertile couples conceiving naturally (time to pregnancy >12 months), and 4317 born after treatment. We defined SGA as the lowest 5% of birth weight by sex and gestational age.
Crude estimates suggested an increased risk of perinatal mortality and SGA among infertile couples (treated and untreated), but the odds ratios (ORs) of perinatal mortality among infertile couples were attenuated after adjustment for maternal age and body mass index [1.32, 95% confidence interval (CI) 0.95–1.84 among untreated and 1.26, 95% CI 0.86–1.85 among treated couples]. The elevated risk of SGA among infertile couples persisted after adjustment for maternal age, parity and smoking (OR 1.24, 95% CI 1.10–1.40 among untreated, and OR 1.40, 95% CI 1.23–1.60 among treated). The risk of SGA increased with time to pregnancy, and a longer time to pregnancy was associated with a small reduction in birth weight across the whole distribution.
The increased risk of SGA observed among infertile couples with or without infertility treatment suggests that infertility may be a risk factor for intrauterine growth restriction. Treatment per se may have little effect on fetal growth. A small to moderate increased risk of perinatal mortality in infertile couples cannot be ruled out due to the small number of cases.
The process of seeking asylum and the related organisational conditions in the host country may adversely affect the children's mental health. The objective of this study was to examine the mental health of children seeking asylum in relation to organisational factors of the asylum system including length of stay and number of relocations.
The population included all 260 parent-accompanied asylum-seeking children aged 4–16 years living in the asylum centres managed by the Danish Red Cross in October–December 2006. Mental health was evaluated using the Strengths and Difficulties Questionnaire. School teachers evaluated children aged 4–16; and the 11–16-year-olds completed the self-report version. To assess the association between organisational factors and mental health, binary logistic regression analyses were done using backwards elimination. We received responses for 246 children equivalent to 95% of the study population.
Using teachers' reports, we found that children who had been asylum-seeking for more than one year in Denmark had an increased risk of having mental difficulties (odds ratio 5.5, 95% CI 1.8–16.3); four or more relocations in the asylum system were also associated with a higher risk (3.0, 1.4–6.7). When the self-report data were included, the associations were even stronger.
Protracted stays at asylum centres and multiple relocations within the asylum system appear to have an adverse effect on asylum-seeking children's mental health. A limit to the duration of the children's stay in the asylum system should be ensured. Follow-up studies with inclusion of other conditions, such as parental mental health and the children's previous trauma, are needed to clarify the influence of the different factors and their interactions.
We have previously observed that an increasing time to pregnancy (TTP) is associated with a reduced frequency of twin deliveries in couples not receiving infertility treatment. By using updated information, we assessed the frequencies of dizygotic and monozygotic twin deliveries as a function of infertility (TTP>12 months), as well as infertility treatment.
From the Danish National Birth Cohort (1997−2003), we identified 51730 fertile couples with TTP=12 months, 5838 infertile couples who conceived naturally with TTP>12 months, and 5163 infertile couples who conceived after treatment. Information on zygosity, available for part of the cohort (1997−2000), was based on standardized questions on the similarities between the twins at the age of 3−5 years.
Compared with fertile couples, the frequency of dizygotic twin deliveries was lower for infertile couples conceiving naturally (Odds ratio 0.4, 95% confidence interval 0.2−0.7) and was much higher for infertile couples conceiving after treatment (17.3, 14.4−20.7). The frequency of dizygotic twin deliveries decreased with TTP in untreated couples, while the frequency of monozygotic twin deliveries remained constant.
The frequency of dizygotic twin deliveries decreased with time to pregnancy and substantially increased with infertility treatment, whereas monozygotic twin deliveries remained substantially unchanged.
infertility; infertility treatment; time to pregnancy; twinning; zygosity
Attention Deficit/Hyperactivity Disorder (ADHD) affects many children, adolescents, and adults and is associated with a number of impairments. Poor academic performance is related to ADHD in clinical samples. However, it is unclear to what extent core ADHD symptoms and scholastic impairment are related in non-referred school-aged children.
Data come from three population-based cohorts from Sweden, Denmark, and Finland, which are part of the Nordic Network on ADHD. The combined sample size was 13,087 children who were studied at ages 7–8 or 10–12 years. Teachers rated children on inattention and hyperactivity symptoms and reported children's scholastic performance on basic skills.
There was a significant association in all cohorts between core ADHD symptoms and scholastic impairment in reading, writing, and mathematics. Particularly, inattention was related to a two to tenfold increase in scholastic impairment. Prevalence of hyperactivity symptoms was similar across the three cohorts, but inattention was lowest among children from the Finnish cohort, after stratification on living conditions.
These results extend previous reports of scholastic impairment among children with clinically diagnosed ADHD to non-referred population samples from three European countries. Surveillance policies should be implemented in school systems to catch children in need of behavioral or scholastic support early.
Objective To estimate the effect of reducing caffeine intake during pregnancy on birth weight and length of gestation.
Design Randomised double blind controlled trial.
Participants 1207 pregnant women drinking at least three cups of coffee a day, recruited before 20 weeks' gestation.
Interventions Caffeinated instant coffee (568 women) or decaffeinated instant coffee (629 women).
Main outcome measures Birth weight and length of gestation.
Results Data on birth weight were obtained for 1150 liveborn singletons and on length of gestation for 1153 liveborn singletons. No significant differences were found for mean birth weight or mean length of gestation between women in the decaffeinated coffee group (whose mean caffeine intake was 182 mg lower than that of the other group) and women in the caffeinated coffee group. After adjustment for length of gestation, parity, prepregnancy body mass index, and smoking at entry to the study the mean birth weight of babies born to women in the decaffeinated group was 16 g (95% confidence interval −40 to 73) higher than those born to women in the caffeinated group. The adjusted difference (decaffeinated group−caffeinated group) of length of gestation was −1.31 days (−2.87 to 0.25).
Conclusion A moderate reduction in caffeine intake in the second half of pregnancy has no effect on birth weight or length of gestation.
Trial registration Clinical Trials NCT00131690.
Objectives To examine whether infertile couples (with a time to pregnancy of > 12 months), who conceive naturally or after treatment, give birth to children with an increased prevalence of congenital malformations.
Design Longitudinal study.
Setting Danish national birth cohort.
Participants Three groups of liveborn children and their mothers: 50 897 singletons and 1366 twins born of fertile couples (time to pregnancy ≤ 12 months), 5764 singletons and 100 twins born of infertile couples who conceived naturally (time to pregnancy > 12 months), and 4588 singletons and 1690 twins born after infertility treatment.
Main outcome measures Prevalence of congenital malformations determined from hospital discharge diagnoses.
Results Compared with singletons born of fertile couples, singletons born of infertile couples who conceived naturally or after treatment had a higher prevalence of congenital malformations—hazard ratios 1.20 (95% confidence interval 1.07 to 1.35) and 1.39 (1.23 to 1.57). The overall prevalence of congenital malformations increased with increasing time to pregnancy. When the analysis was restricted to singletons born of infertile couples, babies born after treatment had an increased prevalence of genital organ malformations (hazard ratio 2.32, 1.24 to 4.35) compared with babies conceived naturally. No significant differences existed in the overall prevalence of congenital malformations among twins.
Conclusions Hormonal treatment for infertility may be related to the occurrence of malformations of genital organs, but our results suggest that the reported increased prevalence of congenital malformations seen in singletons born after assisted reproductive technology is partly due to the underlying infertility or its determinants. The association between untreated infertility and congenital malformations warrants further examination.
We aimed to examine whether exposure to prenatal stress following maternal bereavement is associated with an increased risk of febrile seizures. In a longitudinal population-based cohort study, we followed 1,431,175 children born in Denmark. A total of 34,777 children were born to women who lost a close relative during pregnancy or within 1 year before the pregnancy and they were included in the exposed group. The exposed children had a risk of febrile seizures similar to that of the unexposed children (hazard ratio (HR) 1.00, 95% CI 0.94–1.06). The HRs did not differ according to the nature or timing of bereavement. Our data do not suggest any causal link between exposure to prenatal stress and febrile seizures in childhood.
Prenatal stress; Bereavement; Febrile seizures; Fetal programming; Longitudinal study