Lifecourse relationship between maternal smoking during pregnancy, birth weight, contemporaneous anthropometric measurements and bone mass at 18 years old. The 1993 Pelotas Birth Cohort

BACKGROUND: Maternal smoking during pregnancy is associated with short-term and also long-term harmful effects on offspring. OBJECTIVE: The aim of this study is to evaluate the associations of maternal smoking during pregnancy with offspring bone health at 18 years old, and the role of birth weight and contemporaneous height, weight and body mass index (BMI) in this association. Data from the 1993 Pelotas Birth Cohort were analyzed using path analysis stratified by sex. Adolescents at 18 years old (N = 1512 males, 1563 females). DXA-determined total body bone mineral density (BMD) and bone mineral content (BMC) were assessed at 18 years old. RESULTS: Each additional cigarette smoked during pregnancy was associated with a lower BMC by − 4.20 g in males (95% CI − 8.37; − 0.05), but not in females [− 2.22 g (95% CI − 5.49; 1.04)]; weaker inverse associations were observed for BMD. This inverse association was explained by the influence of maternal smoking on birth weight and contemporaneous anthropometry, particularly height. A 1 kg higher birth weight was associated with a higher BMC by around 144 g in males and by around 186 g in females, and also with a higher BMD by around 0.019 g/cm(2) in males and by around 0.018 g/cm(2) in females, respectively. CONCLUSIONS: Lifecourse analysis using path models has enabled to evaluate the role of mediators in the associations of maternal smoking during pregnancy and birth weight with bone mass in the offspring, thus generating improved understanding of the etiology of bone health and the importance of early life experiences.