Objective: We report on the risk of miscarriage with high- and low-dosage periconceptional folic acid (FA) supplementation from a double-blind randomized clinical trial for prevention of orofacial cleft recurrence in Brazil. Methods: Women at risk of recurrence of orofacial clefts in their offspring were randomized into high (4 mg/day) and low (0.4 mg/day) doses of FA supplementation. The women received the study pills before pregnancy, and supplementation continued throughout the first trimester. Miscarriage rates were compared between the two FA groups and with the population rate. Results: A total of 268 pregnancies completed the study protocol, with 141 in the 4.0-mg group and 127 in the 0.4-mg group. The miscarriage rate was 14.2% in the low-dose FA group (0.4 mg/day) and 11.3% for the high- dose group (4 mg/day) (P = 0.4877). These miscarriage rates are not significantly different from the miscarriage rate in the Brazilian population, estimated to be around 14% (P = 0.311). Conclusions: These results indicate that high- dose FA does not increase miscarriage risk in this population and add further information to the literature on the safety of high FA supplementation for prevention of birth defect recurrence
