Periconceptional multivitamin supplementation containing folic acid and sex ratio at birth in a Chinese population: A prospective cohort study

Abstract

Background To determine whether periconceptional use of multivitamin supplements containing folic acid increases the occurrence of male births in a Chinese population. Methods A prospective cohort study was carried out in 18 counties in four provinces of China. Participants were naturally and voluntarily divided into an intervention group (who took a multivitamin pill containing folic acid, n-=-25-418) and a control group (who did not take any multivitamin, n-=-26-580). Multivitamin supplements containing folic acid was ascertained before pregnancy. Pregnant women were followed through the first trimester of pregnancy and the outcome of pregnancy (i.e. livebirth, stillbirth, or fetal death; sex at birth) was recorded. Results A total of 52-043 pregnancies and 51-998 births were recorded between September 2000 and August 2002. The proportion of males born to women who did and did not take the multivitamin were 54.8% (n-=-13-935) and 54.0% (n-=-11-483), respectively. The male to female sex ratios at birth among women who did and did not take the multivitamin were 117:100 and 121:100, respectively. The risk ratio was 1.03 [95% confidence interval 0.99, 1.06] after adjusting for confounding factors. Conclusions These findings suggest that periconceptional multivitamin supplementation containing folic acid is not associated with an increased likelihood of male births in a Chinese population. However, these results may have been affected by induced abortion or selective termination of pregnancy, and the findings must therefore be cautiously interpreted.