Women are advised to take folic acid (FA) supplements before and during early pregnancy to reduce their risk of a neural tube defect-affected pregnancy. These birth defects occur in the first month of pregnancy, after which there is no proven benefit of continuing FA, yet most women continue to take FA throughout pregnancy. Continuing FA after 12 weeks gestation is associated with an increased risk of adverse outcomes, including gestational diabetes mellitus (GDM). Animal models show a high FA intake in pregnancy promotes insulin resistance, dyslipidemia, and glucose intolerance. GDM affects 1 in 6 Australian pregnancies, but observational and animal studies showing potential harm are insufficient to change policy. Only a high-quality, adequately powered RCT can prove that FA use beyond 12 weeks increases GDM. Accordingly, we are conducting an RCT to determine if stopping FA supplementation after 12 weeks gestation, compared to continuing FA, reduces the risk of developing GDM and related problems (e.g., preterm birth, LGA). Women between 12 -16 weeks’ gestation will be randomized to take a daily prenatal supplement with 500 µg FA and 0 µg FA. The primary outcome is GDM diagnosis, assessed by a 2-h 75 g Oral Glucose Tolerance Test at 24-28 weeks’ gestation. A sample of 2,826 women will yield 90% power to detect a 26% relative reduction in GDM from 18.00% to 13.33% (alpha=0.05). Biological samples will be collected and stored. We will leverage the study to examine the effect of discontinuing folic acid on other maternal and child outcomes.
Tim is a Professor of Nutrition at the Caring Futures Institute at Flinders University in South Australia. Previously, he was a Principal Nutritionist at the South Australian Health and Medical Research Institute Women and Kids Theme (2016-2023), a Professor of Human Nutrition at the University of British Columbia, and a Scientist at BC's Child & Family Research Institute. Within the past five years, Tim has had funding from the Women's and Children's Research Foundation, Nutrition International, the Channel 7 Children's Research Foundation, Australia's National Health and Medical Research Council and Medical Research Futures Fund. His research focuses on micronutrients in pre-pregnancy, pregnancy, lactation, and early life (first 1000 days), and studies have been conducted in Canada, NZ, Australia, Asia, and Africa.