Fetal Exposure to Tobacco Metabolites and Depression During Adulthood: Beyond Binary Measures.

BACKGROUND: Sibling studies of maternal smoking during pregnancy and subsequent risk of depression have produced mixed results. A recent study identified not considering the amount of maternal smoking and age of onset as potentially masking a true association. We examine these issues and also the amount of maternal smoking during pregnancy as a determinant of the severity of depressive symptoms. METHODS: We analyzed data from the community-based National Longitudinal Survey of Youth (US, 1994-2016). Mothers reported smoking during pregnancy (none, <1 pack/day, ≥1 pack/day). We assessed offspring's lifetime depression (i.e., ≥8 symptoms) and symptom counts with the Centers for Epidemiologic Studies Depression scale. We estimated the risk of these two outcomes in the full sample (n = 7172) and among siblings (n = 6145) using generalized linear mixed-effects models with random intercepts by family and family-averaged means for sibling analyses. RESULTS: Among siblings, we observed dose-dependent elevations for both risk of depression (smoking during pregnancy <1 pack/day adjusted risk ratio [aRR] = 1.18; 95% confidence interval [CI] = 1.07, 1.30; smoking ≥1 aRR = 1.36; 95% CI = 1.19, 1.56) and severity of depressive symptoms (smoking <1 pack/day aRR = 1.12; 95% CI = 1.08, 1.16); smoking ≥1 pack/day aRR = 1.25; 95% CI = 1.18, 1.31). Among both samples, the P for trend was <0.01. In analysis limited to offspring diagnosed before age 18, results for severity were attenuated. CONCLUSIONS: This evidence supports the existence of an independent association between maternal smoking during pregnancy and both the risk of depression and the severity of depressive symptoms. The results highlight the utility of considering the amount of smoking, severity of symptoms, and age of onset.

Variation in Breastfeeding Initiation and Duration by Mode of Childbirth: A Prospective, Population-Based Study.

Introduction: Despite known benefits of breastfeeding, including prevention against infections for infants, in the presence of numerous barriers, less than half of infants in high-income countries breastfeed for 6 months. One potential barrier to breastfeeding is birth by cesarean section (C-Section), which can invoke long-term difficulties. However, our structured literature review found that existing empirical research does not fully elucidate this relationship due to differences in operationalization of C-section and breastfeeding, omission of important confounders, and failure to exclude those who did not initiate breastfeeding (or use time-to-event analyses). In this article, we attempt to overcome these limitations. Methods: We analyzed data from 14,414 mother-infant dyads enrolled in the United Kingdom-based prospective Millennium Cohort Study, beginning in 2001. Using multivariable logistic regression, we examined the association between mode of birth (vaginal, emergency C-section, and elective C-section) and likelihood of breastfeeding initiation. We then applied adjusted Accelerated Failure Time survival models to examine the associations between mode of birth and duration of any and exclusive breastfeeding. Results: Those with planned (but not emergency) C-section were less likely to initiate breastfeeding (odds ratio: 0.84, 95% confidence interval [CI]: 0.71-0.99) relative to vaginal births. However, those with either planned or unplanned C-section discontinued both any and exclusive breastfeeding sooner than vaginal births. This effect was more pronounced for those with planned C-section (time ratio [TR]: 0.75, 95% CI: 0.64-0.89) than unplanned C-section (TR: 0.85, 95% CI: 0.74, 0.97) compared with vaginal births. Conclusions: Through application of rigorous methods, this study provides compelling evidence that breastfeeding duration may be impeded by C-section birth. The findings suggest that additional support for mothers who intend to breastfeed and have a C-section birth may be warranted.