The aim of this paper was to review the effects of folic acid supplementation before and throughout pregnancy on fetal development with a focus on studying the effects of correct dosage. Related publications were reviewed to determine and quantify associations of maternal use of folic acid before conception and during pregnancy as risk factor for Neural Tube Defects (NTD), Orofacial Clefts, and ischemic heart diseases. Challenges in global prevalence estimation include quality of surveillance methods, geographic, socioeconomic factors, availability, use of folic acid, ethnic, genetic factors, limitations in education and access to care. For primary prevention of NTD in women with no prior affected pregnancy, 0.4 mg daily dose of folic acid was recommended and 4.0 mg daily dose was effective in preventing NTD in women with a prior affected pregnancy. Maternal supplementation in early pregnancy reduces the risk of oral cleft in infants. Folic acid may prevent or promote cancer development and progression depending on the timing of intervention.