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1.  Patterns of deliveries in a Brazilian birth cohort: almost universal cesarean sections for the better-off 
Revista de saude publica  2011;45(4):635-643.
To describe the patterns of deliveries in a birth cohort and to compare vaginal and cesarean section deliveries.
All children born to mothers from the urban area of Pelotas, Brazil, in 2004, were recruited for a birth cohort study. Mothers were contacted and interviewed during their hospital stay when extensive information on the gestation, the birth and the newborn, along with maternal health history and family characteristics was collected. Maternal characteristics and childbirth care financing – either private or public healthcare (SUS) patients - were the main factors investigated along with a description of C-sections distribution according to day of the week and delivery time. Standard descriptive techniques, χ2 tests for comparing proportions and Poisson regression to explore the independent effect of C-section predictors were the methods used.
The overall C-section rate was 45%, 36% among SUS and 81% among private patients, where 35% of C-sections were reported elective. C-sections were more frequent on Tuesdays and Wednesdays, reducing by about a third on Sundays, while normal deliveries had a uniform distribution along the week. Delivery time for C-sections was markedly different among public and private patients. Maternal schooling was positively associated with C-section among SUS patients, but not among private patients.
C-sections were almost universal among the wealthier mothers, and strongly related to maternal education among SUS patients. The patterns we describe are compatible with the idea that C-sections are largely done to suit the doctor’s schedule. Drastic action is called for to change the current situation.
PMCID: PMC3794425  PMID: 21670862
Parturition; Cesarean Section, trends; Perinatal Care; Obstetrics; Socioeconomic Factors; Cohort Studies.
2.  Maternal smoking and child psychological problems: Disentangling causal and non-causal effects 
Pediatrics  2010;126(1):e57-e65.
To explore associations of maternal prenatal smoking and child psychological problems and determine the role of causal intrauterine mechanisms.
Patients and Methods
Maternal smoking and child psychological problems were explored in 2 birth cohorts in Pelotas, Brazil (n=509; random sub-sample) and Avon Longitudinal Study of Parents and Children (ALSPAC), Britain (n=6,735). Four approaches for exploring causal mechanisms were applied: 1) cross-population comparisons between a high-income and a middle-income country, 2) multiple adjustment for socioeconomic and parental psychological factors, 3) maternal-paternal comparisons as a test of putative intrauterine effects; and 4) search for specific effects on different behavioural subscales.
Socioeconomic patterning of maternal prenatal smoking was stronger in the ALSPAC compared with the Pelotas cohort. Despite this difference in a key confounder, consistency in observed associations was found between these cohorts. In both cohorts, unadjusted, maternal smoking was associated with greater offspring hyperactivity, conduct/externalizing problems, and peer problems, but not with emotional/internalizing problems. After adjusting for confounders and paternal prenatal smoking, only the association with conduct/externalizing problems persisted in both cohorts (conduct problems in the ALSPAC cohort, odds ratio OR: 1.24 [95% confidence interval (CI): 1.07–1.46], p= .005; externalizing problems in the Pelotas cohort, OR:1.82 [95% CI:1.19–2.78], p=.005; ORs reflect ordinal ORs of maternal smokers having offspring with higher scores). Maternal smoking associations were stronger than paternal smoking associations, although statistical evidence for differences was weak in 1 cohort.
Evidence from 4 approaches suggests a possible intrauterine effect of maternal smoking on offspring conduct/externalizing problems.
PMCID: PMC3605780  PMID: 20587678
ALSPAC; Pelotas; prenatal smoking; child; behavioral problems; developmental origins
3.  Prognostic factors for low birthweight repetition in successive pregnancies: a cohort study 
To identify prognostic factors associated with recurrence of low birthweight (LBW) in successive gestations, a study was carried out with a subsample of mothers enrolled in the 2004 Pelotas Birth Cohort.
Data were collected by hospital-based interviews. Newborns were weighed and measured. Gestational age was defined according to the date of last menstrual period, ultra-sound scan before the 20th week of pregnancy or the Dubowitz method. Mothers who reported at least one LBW newborn in the two previous gestations were included. Prevalence ratios (PR) and 95% confidence intervals were estimated from Poisson Regression. All estimates were adjusted for parity.
A total of 4558 births were identified in 2004, and 565 met inclusion criteria, out of which 86 (15.2%) repeated LBW in 2004. Among mothers with two LBW babies before 2004, 47.9% presented LBW recurrence. Belonging to the highest socio-economic stratum (PR 0.89; 0.01-0.46) and gaining ≥ 10 kg during pregnancy (PR 0.09; 0.01-0.77) were protective against LBW recurrence. Higher risk of LBW recurrence was observed among mothers with higher parity (≥3 previous deliveries; PR=1.93; 95% CI 1.23-3.02); who had given birth to a previous preterm baby (PR=4.01; 2.27-7.10); who delivered a female newborn in current gestation (PR=2.61; 1.45-4.69); and that had not received adequate antenatal care (PR=2.57; 1-37-4.81).
Improved quality of antenatal care and adequate maternal weight gain during pregnancy may be feasible strategies to prevent LBW repetition in successive pregnancies.
PMCID: PMC3558483  PMID: 23342985
Prognostic factors; Low birthweight recurrence; Low birthweight; Preterm; Antenatal care
4.  Use of Medicines with Unknown Fetal Risk among Parturient Women from the 2004 Pelotas Birth Cohort (Brazil) 
Journal of Pregnancy  2012;2012:257597.
Background. To estimate the exposure to medicines with unknown fetal risk during pregnancy and to analyze the maternal characteristics associated with it. Methods. A questionnaire was administered to 4,189 mothers of children belonging to the 2004 Pelotas (Brazil) birth cohort study about use of any medicine during gestation. We evaluated the associations between use of medicines with unknown fetal risk and the independent variables through logistic regression models. Unknown fetal risk was defined as medicines in which studies in animals have revealed adverse effects on the fetus, and no controlled studies in women, or studies in women and animals, are available. Results. Out of the 4,189 women, 52.5% used at least one medicine from unknown fetal risk. Use of these medicines was associated with white skin color, high schooling, high income, six or more antenatal care consultations, hospital admission during pregnancy, and morbidity during gestation. Conclusion. The use of unknown fetal risk medicines is high, suggesting that their use must be addressed with caution with the aim of restricting their use to cases in which the benefits are greater than the potential risks.
PMCID: PMC3549362  PMID: 23346403
5.  Breastfeeding and feeding patterns in three birth cohorts in Southern Brazil: trends and differentials 
Breastfeeding is fundamental for child health. Changes in the duration of breastfeeding are compared for three population-based cohorts of children born in 1982, 1993 and 2004 in the city of Pelotas, Southern Brazil. Samples of the 1982 and 1993 children and all of the children from the 2004 cohort study were sought at home when they were aged around 12 months. Both the duration of breastfeeding and the stage at which different kind of foods were regularly introduced were investigated. The median duration of breastfeeding increased from 3.1 to 6.8 months in this period. Exclusive breastfeeding at three months was practically non-existent in 1982 and had reached one third of infants by 2004. The increase was faster after 1993, suggesting an important impact made by promotion activities. Up to about 6-9 months, breastfeeding was more prevalent in high-income families, but after this age it became more common among the poor. Low birth weight babies were breastfeed for shorter durations. The duration of breastfeeding is still far short of international recommendations, justifying further campaigns. Special attention should be given to low birth weight babies and those from low-income families.
PMCID: PMC3532951  PMID: 18797716
Breast Feeding; Child Welfare; Cohort Studies
7.  Life Course Association of Maternal Smoking During Pregnancy and Offspring's Height: Data From the 1993 Pelotas (Brazil) Birth Cohort 
The Journal of Adolescent Health  2012;51(6):S53-S57.
To evaluate the effect of (1) maternal smoking during pregnancy; and (2) partner smoking on offspring's height in infancy, childhood, and adolescence.
All hospital live births from 1993 (5,249) were identified, and these infants were followed up at several ages. Height for age, expressed as z-scores using the World Health Organization growth curves, was measured at all follow-up visits. Maternal smoking during pregnancy was collected retrospectively at birth and analyzed as number of cigarettes/day smoked categorized in four categories (never smoked, <10, 10–19, and ≥20 cigarettes/day). Partner smoking was analyzed as a dichotomous variable (No/Yes). Unadjusted and adjusted analyses were performed by use of linear regression.
The prevalence of self-reported maternal smoking during pregnancy was 33.5%. In the crude analysis, the number of cigarettes/day smoked by the mother during pregnancy negatively affected offspring's height in infancy, childhood, and adolescence. After adjustment for confounders and mediators, this association remained statistically significant, although the magnitude of the regression coefficients was reduced. Paternal smoking was not associated with offspring's height in the adjusted analyses.
In addition to the well-known harmful effects of smoking, maternal smoking during pregnancy negatively affects offspring's height. Public health policies aimed at continuing to reduce the prevalence of maternal smoking during pregnancy must be encouraged.
PMCID: PMC3508408  PMID: 23283162
Smoking; Height by age; Body height; Growth; Child; Adolescent; Cohort studies
8.  Gestational age at birth and morbidity, mortality, and growth in the first 4 years of life: findings from three birth cohorts in Southern Brazil 
BMC Pediatrics  2012;12:169.
We assessed anthropometric status, breastfeeding duration, morbidity, and mortality outcomes during the first four years of life according to gestational age, in three population-based birth cohorts in the city of Pelotas, Southern Brazil.
Total breastfeeding duration, neonatal mortality, infant morbidity and mortality, and anthropometric measures taken at 12 and 48 months were evaluated in children of different gestational ages born in 1982, 1993 and 2004 in Southern Brazil.
Babies born <34 weeks of gestation and those born between 34–36 weeks presented increased morbidity and mortality, were breastfed for shorter periods, and were more likely to be undernourished at 12 months of life, in comparison with the 39–41 weeks group. Children born with 37 weeks were more than twice as likely to die in the first year of life, and were also at increased risk of hospitalization and underweight at 12 months of life. Post-term infants presented an increased risk of neonatal mortality.
The increased risks of morbidity and mortality among preterm (<37 weeks of gestation) and post-term (>41 weeks) are well known. In our population babies born at 37 also present increased risk. As the proportion of preterm and early term babies has increased markedly in recent years, this is a cause for great concern.
PMCID: PMC3504558  PMID: 23114098
Gestational age; Preterm births; Early term births; Post-term births; Infant mortality; Neonatal mortality
9.  Trends in socioeconomic inequalities in anthropometric status in a population undergoing the nutritional transition: data from 1982, 1993 and 2004 pelotas birth cohort studies 
BMC Public Health  2012;12:511.
Socioeconomic inequalities in child nutrition may change rapidly over time, particularly in populations undergoing the nutrition transition. Yet, the few available studies are repeated cross-sectional surveys. By studying three prospective birth cohorts in the same city over a period of more than two decades, we describe secular trends in overweight and stunting at different ages, according to socioeconomic position.
Population-based birth cohort studies were launched in the city of Pelotas (Brazil) in 1982, 1993 and 2004, with follow-up visits at twelve, 24 and 48 months. Children were weighed and measured at every visit. Z-scores of length/height-for-age and body mass index-for-age were calculated using the WHO Child Growth Standards. The slope and relative indices of inequality, based on family income quintiles, were estimated for each follow-up visit.
Between the 1982 and 2004 cohorts, stunting among four-year-olds declined (from 10.9% to 3.6%), while overweight increased (from 7.6% to 12.3%). In every visit, stunting prevalence was inversely related to income. Both absolute and relative inequalities declined over time; among four-year-olds stunting dropped from 26.0% in the 1982 cohort to 6.7% in the 2004 cohort in the poorest group, while in the richest group stunting prevalence dropped from 2.7% in 1982 to 1.1% in the 2004 cohort study. The secular trend towards increased overweight was evident for four-year-olds, in almost all socioeconomic groups, but not among one and two-year-olds. Among four-year old children, overweight prevalence increased in all income quintiles, by 130% in the middle-income group, 64% in the poorest and 41% in the richest group.
The decline in stunting is remarkable, but the increase in overweight among four-year olds – particularly among the poorest and the middle-income groups– requires concerted efforts to prevent the long term consequences of child overweight.
PMCID: PMC3490989  PMID: 22776157
Socioeconomic factors; Health status disparities; Cohort studies; Child nutrition; Overweight; Stunting
10.  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
11.  Food intake profiles of children aged 12, 24 and 48 months from the 2004 Pelotas (Brazil) birth cohort: an exploratory analysis using principal components 
To identify food intake profiles of children during their first four years of life and assess its variations according to sociodemographic and behavioral characteristics.
The Pelotas Birth Cohort Study (Brazil) recruited 4,231 liveborns, who were followed-up at ages 3, 12, 24 and 48 months. Food consumption data of children aged 12, 24 and 48 months was collected using a list of foods consumed during a 24-hour period prior to the interview. The food profiles were identified with the use of principal component analysis (PCA) for each age studied.
Five components were identified at each age, four of them similar in all time points, namely: beverages, milks, staple, and snacks. A meat & vegetables component was identified at 12 and 24 months and a treats component at 48 months. The greatest nutritional differences were found among children from different socioeconomic levels. With regard to the milks component, higher breast milk intake compared to cow's milk was seen among poorer children (12- and 24-month old) and higher milk and chocolate powdered milk drink consumption was seen among more affluent children aged 48 months. Poorer children of less educated mothers showed higher adherence to the treats component (48 months). Regarding to the snack component, poorer children consumed more coffee, bread/cookies while more affluent children consumed proportionately more fruits, yogurt and soft drinks. Child care outside of the home was also a factor influencing food profiles more aligned with a healthier diet.
The study results showed that very early in life children show food profiles that are strongly associated with social (maternal schooling, socioeconomic position and child care) and behavioral characteristics (breast-feeding duration, bottle-feeding and pacifier use).
PMCID: PMC3424118  PMID: 22510615
12.  Measuring socio-economic position for epidemiological studies in low- and middle-income countries: a methods of measurement in epidemiology paper 
Much has been written about the measurement of socio-economic position (SEP) in high-income countries (HIC). Less has been written for an epidemiology, health systems and public health audience about the measurement of SEP in low- and middle-income countries (LMIC). The social stratification processes in many LMIC—and therefore the appropriate measurement tools—differ considerably from those in HIC. Many measures of SEP have been utilized in epidemiological studies; the aspects of SEP captured by these measures and the pathways through which they may affect health are likely to be slightly different but overlapping. No single measure of SEP will be ideal for all studies and contexts; the strengths and limitations of a given indicator are likely to vary according to the specific research question. Understanding the general properties of different indicators, however, is essential for all those involved in the design or interpretation of epidemiological studies. In this article, we describe the measures of SEP used in LMIC. We concentrate on measures of individual or household-level SEP rather than area-based or ecological measures such as gross domestic product. We describe each indicator in terms of its theoretical basis, interpretation, measurement, strengths and limitations. We also provide brief comparisons between LMIC and HIC for each measure.
PMCID: PMC3396323  PMID: 22438428
Socio-economic factors; social class; poverty; measurement; methods; developing countries
13.  Seasonality of infant feeding practices in three Brazilian birth cohorts 
Background We assessed the influence of season of birth on duration of breastfeeding and other feeding patterns in three population-based birth cohort studies in the city of Pelotas, Southern Brazil.
Methods In 1982, 1993 and 2004, all hospital-born children in the city were enrolled in three cohort studies (n = 5914, 5249 and 4287, respectively). Children and their mothers were periodically visited in the first 2 years of life, to collect information on the duration of breastfeeding and the ages at which different types of foods were introduced on a regular basis. Two independent variables were studied: month of birth and mean environmental temperature in the first month of life. Survival analyses and chi-squared tests were used to evaluate the associations. Temperature-based slope indices of inequality were also calculated.
Results Duration of breastfeeding was lower among children born from April to June (months preceding winter) and spending their first month of life in colder temperatures. The influence of season of birth on breastfeeding patterns and the introduction of cow's milk differed according to maternal education, with the strongest effects among children belonging to less educated mothers. Early introduction of fruits (1982 and 1993 cohorts) and vegetables (1982 cohort) were also associated with lower environmental temperature in the first month of life, but not with trimester of birth.
Conclusion Colder temperatures adversely affect duration of breastfeeding and feeding patterns in infancy, especially among the poorest. This finding should be considered in breastfeeding promotion programmes.
PMCID: PMC3396312  PMID: 22354916
Breastfeeding; climate; cohort studies; temperature; supplementary feeding
14.  Maternal smoking during pregnancy and offspring trajectories of height and adiposity: comparing maternal and paternal associations 
Background Maternal smoking during pregnancy is associated with reduced offspring birth length and has been postulated as a risk factor for obesity. Causality for obesity is not established. Causality is well-supported for birth length, but evidence on persistence of height deficits is inconsistent.
Methods We examined the association between maternal smoking during pregnancy and trajectories of offspring height (0–10 years, N = 9424), ponderal index (PI) (0–2 years, N = 9321) and body mass index (BMI) (2–10 years, N = 8887) in the Avon Longitudinal Study of Parents and Children. To strengthen inference, measured confounders were controlled for, maternal and partner smoking associations were compared, dose–response and associations with post-natal smoking were examined.
Results Maternal smoking during pregnancy was associated with shorter birth length, faster height growth in infancy and slower growth in later childhood. By 10 years, daughters of women who smoke during pregnancy are on average 1.11 cm (SE = 0.27) shorter after adjustment for confounders and partner smoking; the difference is 0.22 cm (SE = 0.22) for partner's smoking. Maternal smoking was associated with lower PI at birth, faster PI increase in infancy, but not with BMI changes 2–10 years. Associations were stronger for maternal than partner smoking for PI at birth and PI changes in infancy, but not for BMI changes after 2 years. A similar dose–response in both maternal and partner smoking was seen for BMI change 2–10 years.
Conclusion Maternal smoking during pregnancy has an intrauterine effect on birth length, and possibly on adiposity at birth and changes in height and adiposity in infancy. We do not find evidence of a specific intrauterine effect on height or adiposity changes after the age of 2 years.
PMCID: PMC3396309  PMID: 22407859
Smoking; growth; obesity; pregnancy; child; ALSPAC
15.  Cesarean section and risk of obesity in childhood, adolescence, and early adulthood: evidence from 3 Brazilian birth cohorts123 
Background: The number of cesarean sections (CSs) is increasing in many countries, and there are concerns about their short- and long-term effects. A recent Brazilian study showed a 58% higher prevalence of obesity in young adults born by CS than in young adults born vaginally. Because CS-born individuals do not make contact at birth with maternal vaginal and intestinal bacteria, the authors proposed that this could lead to long-term changes in the gut microbiota that could contribute to obesity.
Objective: We assessed whether CS births lead to increased obesity during childhood, adolescence, and early adulthood in 3 birth cohorts.
Design: We analyzed data from 3 birth-cohort studies started in 1982, 1993, and 2004 in Southern Brazil. Subjects were assessed at different ages until 23 y of age. Poisson regression was used to estimate prevalence ratios with adjustment for ≤15 socioeconomic, demographic, maternal, anthropometric, and behavioral covariates.
Results: In the crude analyses, subjects born by CS had ∼50% higher prevalence of obesity at 4, 11, and 15 y of age but not at 23 y of age. After adjustment for covariates, prevalence ratios were markedly reduced and no longer significant for men or women. The only exception was an association for 4-y-old boys in the 1993 cohort, which was not observed in the other 2 cohorts or for girls.
Conclusion: In these 3 birth cohorts, CSs do not seem to lead to an important increased risk of obesity during childhood, adolescence, or early adulthood.
PMCID: PMC3260073  PMID: 22237058
16.  Childbearing during adolescence and offspring mortality: findings from three population-based cohorts in southern Brazil 
BMC Public Health  2011;11:781.
The role of young maternal age as a determinant of adverse child health outcomes is controversial, with existing studies providing conflicting results. This work assessed the association between adolescent childbearing and early offspring mortality in three birth cohort studies from the city of Pelotas in Southern Brazil.
All hospital births from 1982 (6,011), 1993 (5,304), and 2004 (4,287) were identified and these infants were followed up. Deaths were monitored through vital registration, visits to hospitals and cemeteries. The analyses were restricted to women younger than 30 years who delivered singletons (72%, 70% and 67% of the original cohorts, respectively). Maternal age was categorized into three groups (< 16, 16-19, and 20-29 years). Further analyses compared mothers aged 12-19 and 20-29 years. The outcome variables included fetal, perinatal, neonatal, postneonatal and infant mortality. Crude and adjusted odds ratios (ORs) were estimated with logistic regression models.
There were no interactions between maternal age and cohort year. After adjustment for confounding, pooled ORs for mothers aged 12-19 years were 0.6 (95% CI = 0.4; 1.0) for fetal death, 0.9 (0.6; 1.3) for perinatal death, 1.0 (0.7; 1.6) for early neonatal death, 1.6 (0.7; 3.4) for late neonatal death, 1.8 (1.1; 2.9) for postneonatal death, and 1.6 (1.2; 2.1) for infant death, when compared to mothers aged 20-29 years. Further adjustment for mediating variables led to the disappearance of the excess of postneonatal mortality. The number of mothers younger than 16 years was not sufficient for most analyses.
The slightly increased odds of postneonatal mortality among children of adolescent mothers suggest that social and environmental factors may be more important than maternal biologic immaturity.
PMCID: PMC3207956  PMID: 21985467
pregnancy in adolescence; infant mortality; neonatal mortality; perinatal mortality; fetal mortality; cohort studies
17.  Maternal smoking during pregnancy and offspring growth in childhood: 1993 and 2004 Pelotas cohort studies 
Archives of Disease in Childhood  2011;96(6):519-525.
To explore the effects of maternal smoking during pregnancy on offspring growth using three approaches: (1) multiple adjustments for socioeconomic and parental factors, (2) maternal–paternal comparisons as a test of putative intrauterine effects and (3) comparisons between two birth cohort studies.
Population-based birth cohort studies were carried out in Pelotas, Brazil, in 1993 and 2004. Cohort members were followed up at 3, 12, 24 and 48 months. Multiple linear regression analysis was used to examine the relationships between maternal and paternal prenatal smoking and offspring anthropometric indices. In the 2004 cohort, the association of smoking with trunk length, leg length and leg-to-sitting-height ratio at 48 months was also explored.
Maternal smoking during pregnancy was associated with reduced z scores of length/height-for-age at each follow-up in both cohorts and reduced leg length at 48 months in the 2004 cohort. Children older than 3 months born to smoking women showed a higher body mass index-for-age z score than children of non-smoking women.
The results of this study strongly support the hypothesis that maternal smoking during pregnancy impairs linear growth and promotes overweight in childhood.
PMCID: PMC3093240  PMID: 21377989
18.  What are the causal effects of breastfeeding on IQ, obesity and blood pressure? Evidence from comparing high-income with middle-income cohorts 
Background A novel approach is explored for improving causal inference in observational studies by comparing cohorts from high-income with low- or middle-income countries (LMIC), where confounding structures differ. This is applied to assessing causal effects of breastfeeding on child blood pressure (BP), body mass index (BMI) and intelligence quotient (IQ).
Methods Standardized approaches for assessing the confounding structure of breastfeeding by socio-economic position were applied to the British Avon Longitudinal Study of Parents and Children (ALSPAC) (N ≃ 5000) and Brazilian Pelotas 1993 cohorts (N ≃ 1000). This was used to improve causal inference regarding associations of breastfeeding with child BP, BMI and IQ. Analyses were extended to include results from a meta-analysis of five LMICs (N ≃ 10 000) and compared with a randomized trial of breastfeeding promotion.
Findings Although higher socio-economic position was strongly associated with breastfeeding in ALSPAC, there was little such patterning in Pelotas. In ALSPAC, breastfeeding was associated with lower BP, lower BMI and higher IQ, adjusted for confounders, but in the directions expected if due to socioeconomic patterning. In contrast, in Pelotas, breastfeeding was not strongly associated with BP or BMI but was associated with higher IQ. Differences in associations observed between ALSPAC and the LMIC meta-analysis were in line with those observed between ALSPAC and Pelotas, but with robust evidence of heterogeneity detected between ALSPAC and the LMIC meta-analysis associations. Trial data supported the conclusions inferred by the cross-cohort comparisons, which provided evidence for causal effects on IQ but not for BP or BMI.
Conclusion While reported associations of breastfeeding with child BP and BMI are likely to reflect residual confounding, breastfeeding may have causal effects on IQ. Comparing associations between populations with differing confounding structures can be used to improve causal inference in observational studies.
PMCID: PMC3147072  PMID: 21349903
ALSPAC; breastfeeding; causation; cognition; cohort; Pelotas
19.  Adolescent blood pressure, body mass index and skin folds: sorting out the effects of early weight and length gains 
Although there is longstanding evidence of the short-term benefits of promoting rapid growth for young children in low-income settings, more recent studies suggest that early weight gain can also increase the risk of chronic diseases in adults. This paper attempts to separate the effects of early life weight and length/height gains on blood pressure, body mass index (BMI), sum of skin folds and subscapular/triceps skin fold ratio at 14–15 years of age.
The sample comprised 833 members of a prospective population-based birth cohort from Brazil. Conditional size (weight or height) analyses were used to express the difference between observed size at a given age and expected size based on a regression, including all previous measures of the same anthropometric index. A positive conditional weight or height indicates growing faster than expected given prior size.
Conditional weights at all age ranges were positively associated with most outcomes; each z-score of conditional weight at 4 years was associated with an increase of 6.1 mm in the sum of skin folds (95% CI 4.5 to 7.6) in adolescence after adjustment for conditional length/height. Associations of the outcomes with conditional length/height were mostly negative or non-significant—each z-score was associated with a reduction of 2.4 mm (95% CI −3.8 to −1.1) in the sum of skin folds after adjustment for conditional weight. No associations were found with the skin fold ratio.
The promotion of rapid length/height gain without excessive weight gain seems to be beneficial for long-term outcomes, but this requires confirmation from other studies.
PMCID: PMC3245895  PMID: 21325148
Blood pressure; chronic disease; cohort studies; prospective studies; skinfold thickness; adolescents cg; blood pressure; children; chronic DI; cohort me
20.  Long-Lasting Maternal Depression and Child Growth at 4 Years of Age: A Cohort Study 
The Journal of Pediatrics  2010;157(3-3):401-406.
To investigate the association between sustained maternal depression at 12, 24, and 48 months post-partum and child anthropometry at age of 4 years.
Study design
A total of 99.2% of the 4287 children born in 2004 in Pelotas, Brazil, were enrolled in a cohort study. At 3, 12, 24, and 48 months, mothers were interviewed and provided information on several characteristics. Maternal depression was investigated through the Edinburgh Postnatal Depression Scale (EPDS). Weight-for-age, height-for-age, and weight-for-height z-scores at 48 months, according to World Health Organization growth curves, were the outcomes. Multivariate analyses were conducted through logistic regression.
At the 48-month follow-up, of the 3792 children, prevalence of underweight was 1.7%; stunting, 3.6%; wasting, 0.6%; and overweight, 12.2%. Depression (EPDS ≥13) was observed in 17.9% of the 3748 mothers. Of the mothers, 4.7% were persistently depressed at the 12-, 24-, and 48-month visits. In crude analyses, maternal depression was positively associated with underweight and stunting. After adjustment, maternal depression was not associated with any of the anthropometric indices.
Long-lasting maternal depression at 12, 24, and 48 months post-partum is not a risk factor for impaired child growth or overweight at age of 4 years.
PMCID: PMC2937222  PMID: 20400093
BMI, Body mass index; EPDS, Edinburgh Postnatal Depression Scale; GA, Gestational age; H/A, Height-for-age; LBW, Low birth weight; LMP, Last menstrual period; W/A, Weight-for-age; W/H, Weight-for-height; WHO, World Health Organization
21.  Late preterm birth is a risk factor for growth faltering in early childhood: a cohort study 
BMC Pediatrics  2009;9:71.
Rates of preterm birth are increasing worldwide and this increase is mostly due to infants born between 34 and 36 weeks of gestational age, the so-called "late preterm" births. The aim of this study was to assess the effect of late preterm birth over growth outcomes, assessed when children were 12 and 24 months old.
In 2004, all births taking place in Pelotas (Southern Brazil) were recruited for a cohort study. Late preterm (34/0-36/6 weeks of gestational age) and term children (37/0-42/6 weeks) were compared in terms of weight-for-age, length-for-age and weight-for-length z-scores. Weight-for-age, length-for-age and weight-for-length z-scores below -2 were considered, respectively, underweight, stunting and wasting. Singleton newborns with adequate weight for gestational age at birth, successfully followed-up either at 12 or 24 months of age were analyzed and adjusted odds ratios with 95% confidence intervals calculated through logistic regression.
3285 births were included, 371 of whom were late preterm births (11.3%). At 12 months, prevalence of underweight, stunting and wasting were, respectively, 3.4, 8.7 and 1.1% among late preterm children, against 1.0, 3.4 and 0.3% among term children. At 24 months, correspondent values were 3.0, 7.2 and 0.8% against 0.8, 2.9 and 0.4%. Comparing with the term children, adjusted odds of being underweighted among late preterm children was 2.57 times higher (1.27; 5.23) at 12 months and 3.36 times higher (1.56; 7.23) at 24; of being stunted, 2.35 (1.49; 3.70) and 2.30 (1.40; 3.77); and of being wasted, 3.98 (1.07; 14.85) and 1.87 (0.50; 7.01). Weight gain from birth to 12 and 24 months was similar in late preterm and term children, whereas length gain was higher in the former group in both periods.
Late preterm children grow faster than children born at term, but they are at increased risk of underweight and stunting in the first two years of life. Failure to thrive in the first two years may put them at increased risk of future occurrences of serious morbidity in late childhood and of chronic disease development in adult life.
PMCID: PMC2780991  PMID: 19917121
22.  Bed-Sharing at 3 Months and Breast-Feeding at 1 Year in Southern Brazil 
The Journal of Pediatrics  2009;155(4-4):505-509.
To investigate the association between bedsharing at age 3 months and breastfeeding (BF) at age 12 months.
Study design
Almost all children born in Pelotas, Brazil in 2004 (99.2%) were enrolled in a cohort study. At birth, age 3 months, and age 12 months, mothers were interviewed to gather information on sociodemographic, reproductive, BF, and bedsharing characteristics. Bedsharing was defined as habitual sharing of a bed between mother and child for the entire night or part of the night. The analysis was limited to children from single births who were breastfed at 3 months. Multivariate analyses were carried out using Poisson regression.
Of 4231 live births, 2889 were breastfed at age 3 months. The prevalence of BF at age 12 months was 59.2% in the children who bedshared at 3 months and 44% in those who did not (adjusted prevalence ratio [PR] for weaning= 0.75; 95% confidence interval [CI] = 0.69-0.81; P < .001). Among children who were exclusively breastfed at 3 months, 75.1% of those who also bedshared were still breastfed at age 12 months, versus 52.3% of those who did not bedshare (adjusted PR = 0.63; 95% CI = 0.53- 0.75; P < .001). The adjusted PR was 0.74 (95% CI = 0.60-0.90; P = .003) in children who were predominantly breastfed and 0.83 (95% CI = 0.76-0.90; P < .001) in those who were partially breastfed.
Bedsharing at 3 months protected against weaning up to age 12 months.
PMCID: PMC3420018  PMID: 19595369
BF, Breast-feeding; CI, Confidence interval; DLP, Date of last period; IEN, National Economic Indicator (Brazil); LBW, Low birth weight; PR, Prevalence ratio; SIDS, Sudden infant death syndrome
23.  Inequities in maternal postnatal visits among public and private patients: 2004 Pelotas cohort study 
BMC Public Health  2009;9:335.
The postnatal period is the ideal time to deliver interventions to improve the health of both the newborn and the mother. However, postnatal care shows low-level coverage in a large number of countries. The objectives of this study were to: 1) investigate inequities in maternal postnatal visits, 2) examine differences in postnatal care coverage between public and private providers and 3) explore the relationship between the absence of maternal postnatal visits and exclusive breastfeeding, use of contraceptive methods and maternal smoking three months after birth.
In the calendar year of 2004 a birth cohort study was started in the city of Pelotas, Brazil. Mothers were interviewed soon after delivery and at three months after birth. The absence of postnatal visits was defined as having no consultations between the time of hospital discharge and the third month post-partum. Logistic regression analysis was used to estimate the association between absence of postnatal visits and type of insurance scheme adjusting for potential confounding factors.
Poorer women, black/mixed, those with lower level of education, single mothers, adolescents, multiparae, smokers, women who delivered vaginally and those who were not assisted by a physician were less likely to attend postnatal care. Postnatal visits were also less frequent among women who relied in the public sector than among private patients (72.4% vs 96% among public and private patients, respectively, x2 p < 0.001) and this difference was not explained either by maternal characteristics or by health care utilization patterns. Women who attended postnatal visits were more likely to exclusively breastfeed their infants, to use contraceptive methods and to be non-smokers three months after birth.
Postpartum care is available for every woman free of charge in the Brazilian Publicly-funded health care system. However, low levels of postpartum care were seen in the study (77%). Efforts should be made to increase the percentage of women receiving postpartum care, particularly those in socially disadvantaged groups. This could include locally-adapted health education interventions that address women's beliefs and attitudes towards postpartum care. There is a need to monitor postpartum care and collected data should be used to guide policies for health care systems.
PMCID: PMC2749044  PMID: 19751521
24.  Differentials and income-related inequalities in maternal depression during the first two years after childbirth: birth cohort studies from Brazil and the UK 
Depression is a prevalent health problem among women during the childbearing years. To obtain a more accurate global picture of maternal postnatal depression, studies that explore maternal depression with comparable measurements are needed. The aims of the study are: (1) to compare the prevalence of maternal depression in the first and second year postpartum between a UK and Brazilian birth cohort study; (2) to explore the extent to which variations in the rates were explained by maternal and infant characteristics, and (3) to investigate income-related inequalities in maternal depression after childbirth in both settings.
Population-based birth cohort studies were carried out in Avon, UK in 1991 (ALSPAC) and in the city of Pelotas, Brazil in 2004, where 13 798 and 4109 women were analysed, respectively. Self-completion questionnaires were used in the ALSPAC study while questionnaires completed by interviewers were used in the Pelotas cohort study. Three repeated measures of maternal depression were obtained using the Edinburgh Postnatal Depression Scale in the first and second year after delivery in each cohort. Unadjusted and adjusted analyses were carried out. The Relative index of Inequality was used for the analysis of income-relate inequalities so that results were comparable between cohorts.
At both the second and third time assessments, the likelihood of being depressed was higher among women from the Pelotas cohort study. These differences were not completely explained by differences in maternal and infant characteristics. Income-related inequalities in maternal depression after childbirth were high and of similar magnitude in both cohort studies at the three time assessments.
The burden of maternal depression after childbirth varies between and within populations. Strategies to reduce income-related inequalities in maternal depression should be targeted to low-income women in both developed and developing countries.
PMCID: PMC2698823  PMID: 19500361
25.  Socioeconomic position and overweight among adolescents: data from birth cohort studies in Brazil and the UK 
BMC Public Health  2009;9:105.
Developed and developing countries are facing rapid increases in overweight and obesity among children and adolescents. The patterns of overweight/obesity differ by age, sex, rural or urban residence and socioeconomic position (SEP) and vary between and within countries.
We investigated patterns of SEP – overweight status association among adolescents from the UK (ALSPAC) and Brazil (the 1982 and 1993 Pelotas birth cohort studies).
All analyses were performed separately for males and females. Logistic regression analysis was used to examine the relationships between overweight status and two SEP indicators – family income and maternal education.
A strong positive association was observed in 11-year-old boys from the 1993 Pelotas cohort, with higher prevalence of overweight among the least poor and among those whose mothers had more years of schooling (x2 for linear trend p < 0.001). In ALSPAC study higher prevalence of overweight was seen among boys whose mothers had lower educational achievement (x2 for linear trend p = 0.006). Among 11 year-old girls from 1993 Pelotas cohort study there was a positive association (higher prevalence of overweight in the higher socioeconomic and educational strata, x2 for linear trend p < 0.001 and p = 0.01, respectively) while an inverse association was found in the ALSPAC study (x2 for linear trend p < 0.001). Among males from the 1982 cohort study, overweight at 18 years of age showed a positive association with both SEP indicators while among females, the reverse association was found.
The results of this study demonstrate that the social patterning of overweight varies between and within populations over time. Specific approaches should be developed within populations in order to contain the obesity epidemic and reduce disparities.
PMCID: PMC2673220  PMID: 19368733

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