Maternal Smoking, Breastfeeding, and Risk of Childhood Overweight: Findings from a National Cohort

To examine the association between exposure to tobacco compounds in breast milk and risk of childhood overweight, we used historical data for a subset of 21,063 mother–child pairs in the US Collaborative Perinatal Project. Based on self-reports, mothers were classified as non-smokers, light (1–9 cigarettes/day), moderate (10–19), or heavy (20+) smokers. Feeding type (exclusive breastfeeding or bottle-feeding) was observed during nursery stay after birth. We stratified children by maternal smoking and feeding type, and then fit interaction terms to isolate exposure to tobacco compounds via breast milk from exposure in uterus and in ambient air after birth. Using measured weight and height, overweight at age 7 was defined as a body mass index ≥85th percentile by sex and age. Among exclusively bottle-fed children, adjusted odds ratios (ORs) of overweight at age 7 were 1.24 (95 % confidence interval [CI], 1.12–1.38; vs. non-smoking) for light maternal smoking, 1.43 (95 % CI, 1.25–1.63) for moderate maternal smoking, and 1.46 (95 % CI, 1.28–1.66) for heavy maternal smoking. Among exclusively breastfed children, the corresponding ORs were 1.33 (95 % CI, 0.96–1.84) for light, 1.86 (95 % CI, 1.27–2.73) for moderate, and 2.22 (95 % CI, 1.53–3.20) for heavy maternal smoking. There was a modest positive interaction between breastfeeding and heavy maternal smoking on overweight risk at age 7. Tobacco compounds via breast milk of smoking mothers (significantly for heavy smokers) appear to be associated with a modest elevation in childhood overweight risk at 7 years of age. More aggressive intervention is needed to help pregnant and breastfeeding women to quit smoking.     

Smoking,physical exercise,BMI and late foetal death: a study within the Danish National Birth Cohort

The aim of this paper was to estimate the effect of maternal and paternal smoking on foetal death (miscarriage and stillbirth) and to estimate potential interactions with physical exercise and pre-pregnancy body mass index. We selected 87,930 pregnancies from the population-based Danish National Birth Cohort. Information about lifestyle, occupational, medical and obstetric factors was obtained from a telephone interview and data on pregnancy outcomes came from the Danish population based registries. Cox regression was used to estimate the hazard ratios (adjusted for potential confounders) for predominantly late foetal death (miscarriage and stillbirth). An interaction contrast ratio was used to assess potential effect measure modification of smoking by physical exercise and body mass index. The adjusted hazard ratio of foetal death was 1.22 (95 % CI 1.02–1.46) for couples where both parents smoked compared to non-smoking parents (miscarriage: 1.18, 95 % CI 0.96–1.44; stillbirth: 1.32, 95 % CI 0.93–1.89). On the additive scale, we detected a small positive interaction for stillbirth between smoking and body mass index (overweight women). In conclusion, smoking during pregnancy was associated with a slightly higher hazard ratio for foetal death if both parents smoked. This study suggests that smoking may increase the negative effect of a high BMI on foetal death, but results were not statistically significant for the interaction between smoking and physical exercise.     

妊娠期被动吸烟与出生缺陷关系的Meta分析

目的探讨孕期被动吸烟与出生缺陷的关系。方法运用计算机检索1980年至2010年4月国内外关于孕期被动吸烟与出生缺陷关系的研究文献,采用Cochrane协作网提供的RevMan5.0分析软件对入选的文献进行异质性检验,经Meta分析计算合并效应OR值及其95%CI。结果国内外25篇文献入选。森林图显示纳入文献是异质的(χ2=243.98,P0.000 01),采用随机效应模型计算孕期被动吸烟与出生缺陷关联性的合并效应的OR值为1.70,95%CI:1.34~2.15。其中,国内和国外不同研究人群合并效应的OR值分别为3.62(95%CI:1.71~7.68)和1.28(95%CI:1.04~1.57)。结论孕期被动吸烟可能会增加出生缺陷发生风险。     

Birth Weight,Maternal Body Mass Index,and Early Childhood Growth: A Prospective Birth Cohort Study in China

Background

The relations of birth weight and maternal body mass index (BMI) to overweight remain unresolved. We prospectively examined the relations of birth weight with various anthropometric measures at age 3 to 6 years, the effect of maternal BMI, and the patterns of these relations in an analysis using 9 birth weight categories.

Methods

The subjects were 210 172 singleton infants born alive with a gestational age ≥28 weeks between October 1993 and December 1996; the subjects were followed up in 2000. Birth weight, maternal height and weight, and other relevant information were measured or collected prospectively. Overweight and underweight were defined by using National Center for Health Statistics/World Health Organization reference data. Logistic regression models were used to estimate relative risks. Analyses stratified by quartile of maternal BMI were performed to examine the effects of maternal BMI on the associations of birth weight with overweight and underweight.

Results

Birth weight was linearly associated with height, weight, and BMI at age 3–6 years. Adjustment for maternal BMI did not alter this association. Birth weight was positively associated with overweight and negatively associated with underweight. The relation curves for both overweight and underweight resembled half of a flat parabolic curve. The associations for overweight and underweight were slightly stronger for the highest and lowest quartiles of maternal BMI, respectively.

Conclusions

Higher birth weight is associated with an increased risk for childhood overweight, and lower birth weight with an increased risk for underweight. The associations between birth weight and early childhood anthropometric growth measures could not explained by maternal BMI.Key words: birth weight, overweight, underweight, maternal body mass index     

Hospital Work and Pregnancy Outcomes: A Study in the Danish National Birth Cohort

Abstract

In hospitals, women of reproductive age do a range of work tasks, some of which are known to carry potential risks. Tasks such as working with radiation, chemicals, and infectious agents, as well as performing heavy lifting or tasks requiring erratic sleep patterns have been reported to increase the risk of reproductive failures. Our aim was to study pregnancy outcomes in female hospital workers in Denmark. We performed a cohort study of 5976 female hospital workers and used as a reference group 60,890 women employed outside of hospitals. The reproductive health of hospital workers working during pregnancy is comparable to those of non-hospital workers for the majority of reproductive failures studied. However, an increased prevalence of congenital abnormalities was noted in some subgroups of hospital workers, which may indicate that some hospital work still entails fetotoxic hazards.     

A Longitudinal Analysis of Adolescent Smoking and its Correlates

ABSTRACT: When designing effective programs, it is important to identify factors associated with tobacco use at particular stages of adolescence, as well as factors associated with changes in tobacco use. This study examined cross-sectional correlates of smoking during early adolescence and during late adolescence in a longitudinal sample to compare the pattern of prediction of smoking at both stages. Changes in predictor variables related to changes in smoking also were examined. Results showed intentions to smoke was the strongest predictor of smoking during both early adolescence and during late adolescence; however, it was a much stronger predictor for the late adolescent stage. In addition, intentions to smoke was the strongest predictor of changes in smoking. However, the pattern of prediction at the two grade levels showed some differences as did predictors of changes in smoking. Implications for designing smoking prevention and cessation programs are addressed.     

Perfluorinated chemicals and fetal growth: a study within the Danish National Birth Cohort

Background

Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) are man-made, persistent organic pollutants widely spread throughout the environment and human populations. They have been found to interfere with fetal growth in some animal models, but whether a similar effect is seen in humans is uncertain.

Objectives

We investigated the association between plasma levels of PFOS and PFOA in pregnant women and their infants’ birth weight and length of gestation.

Methods

We randomly selected 1,400 women and their infants from the Danish National Birth Cohort among those who completed all four computer-assisted telephone interviews, provided the first blood samples between gestational weeks 4 and 14, and who gave birth to a single live-born child without congenital malformation. PFOS and PFOA were measured by high performance liquid chromatography–tandem mass spectrometer.

Results

PFOS and PFOA levels in maternal plasma were on average 35.3 and 5.6 ng/mL, respectively. Only PFOA levels were inversely associated with birth weight (adjusted β = −10.63 g; 95% confidence interval, −20.79 to −0.47 g). Neither maternal PFOS nor PFOA levels were consistently associated with the risk for preterm birth or low birth weight. We observed no adverse effects for maternal PFOS or PFOA levels on small for gestational age.

Conclusion

Our nationwide cohort data suggest an inverse association between maternal plasma PFOA levels and birth weight. Because of widespread exposure to these chemicals, our findings may be of potential public health concern.     

Subfecundity as a correlate of preeclampsia: a study within the Danish National Birth Cohort

A long interpregnancy interval is associated with preeclampsia. If some women experiencing a long interval between births had difficulty conceiving, subfecundity and preeclampsia may share a common etiology. Therefore, the authors examined the association between subfecundity and preeclampsia. By using interview data collected during the second trimester of pregnancy (1998-2001) from women participating in the Danish National Birth Cohort, they identified 20,034 and 24,698 singleton livebirths to primiparous and multiparous women, respectively, for whom preeclampsia information was available from hospital birth records. Among women with no known hypertension, the authors estimated a higher risk of preeclampsia in those with longer times to pregnancy (TTPs), after adjustment for maternal age, prepregnancy body mass index, and smoking. Compared with primiparas who became pregnant right away (referent category), the risk of preeclampsia increased with TTP and then stabilized for women taking 6 months or longer to conceive, whose risk of preeclampsia increased by 50%. Multiparas also had an increased risk, but only those reporting a TTP longer than 12 months (odds ratio = 2.47, 95% confidence interval: 1.30, 4.69). The authors found that a long TTP was associated with preeclampsia, supporting the hypothesis that some factors delaying clinically recognized conception may also be in a causal pathway for preeclampsia.     

Maternal common mental disorders and infant development in Ethiopia: the P-MaMiE Birth Cohort

Background  

Chronicity and severity of early exposure to maternal common mental disorders (CMD) has been associated with poorer infant development in high-income countries. In low- and middle-income countries (LAMICs), perinatal CMD is inconsistently associated with infant development, but the impact of severity and persistence has not been examined.     

Maternal Dietary Patterns during Pregnancy in Relation to Offspring Forearm Fractures: Prospective Study from the Danish National Birth Cohort

Limited evidence exists for an association between maternal diet during pregnancy and offspring bone health. In a prospective study, we examined the association between dietary patterns in mid-pregnancy and offspring forearm fractures. In total, 101,042 pregnancies were recruited to the Danish National Birth Cohort (DNBC) during 1996–2002. Maternal diet was collected by a food frequency questionnaire. Associations were analyzed between seven dietary patterns extracted by principal component analysis and offspring first occurrence of any forearm fracture diagnosis, extracted from the Danish National Patient Register, between time of birth and end of follow-up (<16 year) (n = 53,922). In multivariable Cox regression models, offspring of mothers in the fourth vs. first quintile of the Western pattern had a significant increased risk (Hazard ratio, 95% confidence interval: 1.11, 1.01–1.23) of fractures, and there was a borderline significant positive trend (p = 0.06). The other dietary patterns showed no associations and neither did supplementary analyses of macro- and micronutrients or single food groups, except for the intake of artificially sweetened soft drinks, which was positively associated with offspring forearm fractures (p = 0.02). In the large prospective DNBC high mid-pregnancy consumption of Western diet and artificially sweetened soft drinks, respectively, indicated positive associations with offspring forearm fractures, which provides interesting hypotheses for future research.     

Laboratory work and pregnancy outcomes: a study within the National Birth Cohort in Denmark

Aims

To examine pregnancy outcomes in women doing laboratory work.

Methods

Using data from the Danish National Birth Cohort (1997–2003), the authors conducted a prospective cohort study of 1025 female laboratory technicians and 8037 female teachers (as reference). The laboratory technicians were asked about laboratory work tasks during pregnancy in an interview (at around 16 weeks of gestation). Pregnancy outcomes were obtained by linking the cohort to the national registers. Hazard ratios (HRs) of late fetal loss and diagnosing of congenital malformations were calculated by using Cox regression, and odds ratios (ORs) of preterm birth and small for gestational age were calculated by using logistic regression.

Results

Overall, there were no significant differences in pregnancy outcomes between laboratory technicians and teachers. However, we found that laboratory technicians working with radioimmunoassay or radiolabelling had an increased risk of preterm birth (OR = 2.2, 95% CI 0.8 to 6.2 for radioimmunoassay, and OR = 1.9, 95% CI 0.8 to 4.6 for radiolabelling) and “major” malformations (HR = 2.1, 95% CI 1.0 to 4.7 for radioimmunoassay, and HR = 1.8, 95% CI 0.9 to 3.7 for radiolabelling). The ORs of preterm birth doubled for women working with these tasks every day or several times a week. When an exposure matrix was applied, an increased risk of “major” malformations for exposure to organic solvents was seen.

Conclusions

The results did not indicate any high risk of reproductive failures in laboratory technicians in general. Exposure to radioisotopes may carry a high risk of preterm birth and congenital malformations. This finding deserves further investigation.     

Fetal growth indicators and perfluorinated chemicals: a study in the Danish National Birth Cohort

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are widespread persistent organic pollutants that have been associated with reduced birth weight at doses expected in many pregnant populations. The authors randomly selected 1,400 pregnant women and their newborns from the Danish National Birth Cohort (1996-2002) to investigate whether these compounds reduce organ growth. PFOS and PFOA were measured in maternal blood samples taken early in pregnancy. Placental weight, birth length, and head and abdominal circumferences were measured shortly after birth by trained midwives or nurses. Maternal PFOA levels in early pregnancy were associated with smaller abdominal circumference and birth length. For each ng/ml increase in PFOA, birth length decreased by 0.069 cm (95% confidence interval: 0.024, 0.113) and abdominal circumference decreased by 0.059 cm (95% confidence interval: 0.012, 0.106). An inverse association was also observed between PFOA and placental weight and head circumference, and a positive association was observed with newborn ponderal index, but none of these associations was statistically significant. Maternal PFOS levels were not associated with any of the five fetal growth indicators. These findings suggest that fetal exposure to PFOA but not PFOS during organ development may affect the growth of organs and the skeleton.     

Maternal Health Literacy and Late Initiation of Immunizations Among an Inner-City Birth Cohort

To determine if maternal health literacy influences early infant immunization status. Longitudinal prospective cohort study of 506 Medicaid-eligible mother-infant dyads. Immunization status at age 3 and 7 months was assessed in relation to maternal health literacy measured at birth using the Test of Functional Health Literacy in Adults (short version). Multivariable logistic regression quantified the effect of maternal health literacy on immunization status adjusting for the relevant covariates. The cohort consists of primarily African-American (87%), single (87%) mothers (mean age 23.4 years). Health literacy was inadequate or marginal among 24% of mothers. Immunizations were up-to-date among 73% of infants at age 3 months and 43% at 7 months. Maternal health literacy was not significantly associated with immunization status at either 3 or 7 months. In multivariable analysis, compared to infants who had delayed immunizations at 3 months, infants with up-to-date immunizations at 3 months were 11.3 times (95%CI 6.0–21.3) more likely to be up-to-date at 7 months. The only strong predictors of up-to-date immunization status at 3 months were maternal education (high school graduate or beyond) and attending a hospital-affiliated clinic. Though maternal health literacy is not associated with immunization status in this cohort, later immunization status is most strongly predicted by immunization status at 3 months. These results further support the importance of intervening from an early age to ensure that infants are fully protected against vaccine preventable diseases.     

Infertility, infertility treatment and psychomotor development: the Danish National Birth Cohort

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.     

Maternal Fish Consumption and Infant Birth Size and Gestation: New York State Angler Cohort Study

Background  

The scientific literature poses a perplexing dilemma for pregnant women with respect to the consumption of fish from natural bodies of water. On one hand, fish is a good source of protein, low in fat and a rich source of other nutrients all of which have presumably beneficial effects on developing embryos and fetuses. On the other hand, consumption of fish contaminated with environmental toxicants such as polychlorinated biphenyls (PCBs) has been associated with decrements in gestation and birth size.