Vitamin D sufficiency during pregnancy helps keep balance of infant sex ratio

A healthy vitamin D status may help combat systemic inflammation in mothers that could otherwise impair the implantation or survival of male fetuses in utero, a recent study has found.

The researchers enrolled 1,191 women attempting pregnancy, in whom preconception levels of 25-hydroxyvitamin D (25(OH)D) were measured using enzyme-linked immunosorbent assays. The primary outcome of interest was offspring sex ratio, assessed through medical charts.

The average 25(OH)D level was 30.8±12.2 ng/mL, with more than half (53 percent) of the women classified as vitamin D insufficient. There was a total of 1,094 livebirths eligible for analysis, including eight twin gestations.

Participants who had sufficient prepregnancy levels of serum 25(OH)D were more than 20-percent more likely to give birth to male infants than comparators with levels below the referent value (adjusted relative risk [RR], 1.26, 95 percent confidence interval [CI], 1.03–1.53).

In absolute terms, vitamin D sufficiency vs insufficiency correlated with 5.60 more male infants per 100 women.

In contrast, vitamin D status had no clear impact on the proportion of female births. Stratifying the sample according to prepregnancy levels of high-sensitivity C-reactive protein, the researchers saw that the impact of vitamin D status was stronger in women with elevated inflammation, suggesting that vitamin D could counteract inflammatory dysregulation in pregnancy that could impair the conception and survival of male infants.

Further accounting for pregnancy and live births did not meaningfully change the initial findings.

“[T]hese findings shed light on the influence of maternal nutrition on offspring sex ratio in humans and lend additional evidence to the importance of the health status of women attempting to conceive, for whom vitamin D and inflammation status could impact the chances of establishing and maintaining a pregnancy after producing a male conceptus,” the researchers said.