Do folic acid levels affect rate of miscarriage?





Related Monographs

Consumer Data: Folic Acid
Professional Data: Folic Acid


Folic acid, also known as folate and folinic acid, is a member of the B-vitamin group and is water-soluble. It occurs in a wide variety of foods including dark green leafy vegetables, brewer's yeast, liver, and eggs. Other good sources are beets, broccoli, brussels sprouts, orange juice, cabbage, cauliflower, cantaloupe, kidney and lima beans, wheat germ, and whole grain cereals and breads. There are no known toxicities with folic acid but researchers know that if the dosage is too high, it could hide a B 12 deficiency.1 This condition is remedied by dosage requirements and at levels above 800mcg, folic acid becomes a prescription.
While it has long been known that folic acid is an important nutrient, it has only been in the past thirty years or so that the role of folic acid in pregnancy has been evaluated. To date, we know that use of folic acid during pregnancy can eliminate the chance of the fetus developing neural tube defects such as spina bifida because this nutrient is responsible for closing the neural tube. This valuable information has made folic acid supplementation during pregnancy a standard part of the education and treatment process.
While these thirty years have provided a good body of research, much remains unknown. Other areas that remain unknown are the potential side effects such as miscarriage. To determine if there is a relationship between the use of folic acid and miscarriage, scientists in China decided to evaluate a large group of pregnant women using folic acid.
During the initial planning stages of the study, almost 24,000 women had enrolled in a national campaign throughout China to prevent neural-tube defects via folic acid supplementation at a level of 400 micrograms per day. The RDA (Recommended Daily Allowance) for adults in the US is 400mcg and for women who are pregnant, the recommended dose in the US is 600mcg.
The rate of miscarriage was followed among women with confirmed pregnancies who had both taken their folic acid supplementation and those who had not taken their folic acid supplementation. The overall rate of miscarriage was 9.1%. The rate of miscarriage among women who utilized folic acid supplementation before and during the first trimester of pregnancy was 9.0%. The rate of miscarriage among women who had not utilized the folic acid supplementation before and during the first trimester of pregnancy was 9.3%. The study coordinators have concluded, "in this population-based study of a cohort of women whose use of folic acid supplements while pregnant had been previously documented and who had been pregnant for the first time, we found no evidence that daily consumption of 400 mcg of folic acid before and during early pregnancy influenced their risk for miscarriage."2
With such a large population sample to study, this information appears to be conclusive because the numbers were not statistically significant between the groups.


1. Stabler SP, et al. Vitamin B-12 deficiency in the elderly: current dilemmas. American Journal of Clinical Nutrition. 1997;Vol 66, 741-749.
2. Gindler J. Folic acid supplements during pregnancy and risk of miscarriage. Lancet. Sep 2001;358(9284):796-800.