Folic acid is involved in gametogenesis, fertilisation and pregnancy, and thus may play an important role in human reproduction.
In the 1990s it was recommended that folic acid be given between a dose of 0.4 and 0.8 mg to prevent neural tube defects. There were some controversial studies in the mid-1990s that may have suggested that folic acid supplementation may increase spontaneous abortion. This was successfully challenged by other studies, and in the recent Cochrane review, based on three randomised control trials, suggested that folic acid in both doses of 0.8 mg and 0.4 mg in two studies, plus a multivitamin supplementation before and during pregnancy, did not increase abortion rates.
In another observational study called the Nurse Study 2 (NHS 2) suggested reduced spontaneous abortion risk among women using folic acid before or during early pregnancy particularly, and recommended that this be taken.