The role of maternal preconception adiposity in human offspring sex and sex ratio.

OBJECTIVE
Determine relations between preconception adiposity and human offspring sex and sex ratio.


METHODS
Within a prospective preconception cohort nested within a randomized controlled trial based at 4 U.S. clinical sites, logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs) for male:female sex ratio and log-identity regression estimated risk differences (RDs) and 95% CIs for male and female live birth by preconception adiposity measures. Inverse probability weights accounted for potential selection bias.


RESULTS
Among 603 women attempting pregnancy, there were meaningful reductions in sex ratio for the highest category of each adiposity measure. The lowest sex ratios were observed for obesity (BMI≥30 kg/m2) (OR = 0.48, 95% CI 0.26, 0.88) relative to normal BMI, and the top tertiles (T3) of leptin and skinfolds (OR = 0.50, 95% CI 0.32, 0.80 and 0.50, 95% CI 0.32, 0.79, respectively) relative to the lowest tertiles. Reductions were driven by 11-15 fewer male live births per 100 women (RD = -15, 95% CI -23, -6.7 for obesity, -11, 95% CI -20, -3.2 for T3 leptin and -11, 95% CI -19, -3.3 for T3 skinfolds).


CONCLUSIONS
Relations between preconception adiposity measures and reduced sex ratio were driven by a reduction in males.