Paternal weight prior to conception and infant birthweight: a prospective cohort study

BACKGROUND/OBJECTIVE: Previous studies have consistently demonstrated that maternal weight status both before and during pregnancy is associated with infant birthweight. However, a fundamental limitation across this literature remains that previous studies have not evaluated the concomitant impact of paternal weight at conception, owing to the paucity of studies in which fathers were assessed prior to pregnancy. Thus, we established a cohort of preconception couples to prospectively evaluate the associations of maternal and paternal weight prior to pregnancy with infant birthweight at delivery. METHODS: In this prospective observational cohort study, 1292 newly-married women and their partners in Liuyang, China, were assessed at median of 23.3 weeks before a singleton pregnancy, thereby enabling concomitant assessment of preconception maternal and paternal body mass index (BMI) in relation to infant birthweight. RESULTS: Mean birthweight was 3294 ± 450 g with 147 neonates (11.4%) born large-for-gestational-age (LGA) and 94 (7.3%) small-for-gestational-age (SGA). After adjustment for maternal and paternal factors prior to conception (age, education, smoking, BMI, household income), length of gestation, total gestational weight gain, gestational diabetes, preeclampsia, and infant sex, it was noted that infant birthweight increased by 42.2 g (95% CI 29.5–54.8; p < 0.0001) per unit increase in maternal pregravid BMI and 10.7 g (95% CI 0.5–20.9; p = 0.04) per unit increase in paternal pregravid BMI. Maternal pregravid BMI explained 6.2% of the variance in birthweight whereas paternal BMI explained only 0.7%. Independent predictors of LGA delivery were maternal pregravid BMI (aOR = 1.91, 95% CI 1.50–2.44), maternal age (aOR = 1.48, 95% CI 1.09–2.00), and gestational weight gain (aOR = 1.80, 95% CI 1.40–2.30). Paternal pregravid BMI was not independently associated with LGA or SGA. CONCLUSION: Paternal BMI prior to conception is associated with infant birthweight but only modestly so, in contrast to the dominant impact of maternal BMI prior to conception.