(P27-101-25) Duration of Folic Acid Supplementation and Pregnancy Outcomes: A Prospective Multicenter Cohort Study in China

Objectives: Folic acid supplementation (FAS) before and in early pregnancy prevents neural tube defects, but the benefits of extending FAS to late-pregnancy on pregnancy outcomes remains unclear. We aimed to investigate the associations between duration of FAS and a spectrum of pregnancy outcomes, and to determine whether the associations were modified by maternal age or pre-pregnancy body mass index (BMI).

Methods: Data on 15,694 singleton pregnant women were drawn from a prospective multi-center cohort conducted from 2017 to 2021 at eight hospitals in China. Two-level mixed-effect log binomial regression models were used to estimate the risk ratios (RRs) and 95% confidential intervals (CIs) for pregnancy complications according to FAS durations till mid-pregnancy, and for birth outcomes till late-pregnancy.

Results: Among 15,694 included women, 4523 (28.8%) had no FAS peri- or during pregnancy (no-FAS), 2854 (18.2%) supplemented only during peri-pregnancy (peri-FAS), 921 (5.9%) from peri- to mid-pregnancy (mid-FAS) and 7396 (47.0%) consecutively to late-pregnancy (late-FAS). Compared with no-FAS, peri-FAS reduced the risk of macrosomia (adjusted RR 0.85, 95% CI 0.84, 0.97); mid-FAS reduced the risks of gestational hypertensive disorders (GHDs) (adjusted RR 0.84, 95% CI 0.74, 0.96) and preeclampsia (adjusted RR 0.81, 95% CI 0.67, 0.97); late-FAS reduced the risk of preterm birth (adjusted RR 0.66, 95% CI 0.58, 0.75), macrosomia (adjusted RR 0.88, 95% CI 0.79, 0.97), SGA (adjusted RR 0.82, 95% CI 0.70, 0.97) and LGA (adjusted RR 0.81, 95% CI 0.73, 0.90). Among women with advanced maternal age or overweight/obesity, mid-FAS increased the risk of GDM (advanced maternal age: adjusted RR 1.12, 95% CI 1.02, 1.23; overweight/obesity: adjusted RR 1.30, 95% CI 1.11, 1.52).

Conclusions: Extending FAS to mid-pregnancy decreased risks of GHDs and preeclampsia, and decreased risks of adverse birth outcomes when extending to late-pregnancy. These findings support extending FAS to late-pregnancy, whereas women with advanced maternal age and overweight/obesity should be cautious on prolonging FAS.

Funding Sources: The National Natural Science Foundation of China (grant number 81801542)
Clinical Medicine Plus X—Young Scholars Project, Peking University