Vitamin supplements do not prevent miscarriage

Clinical question: 
How effective are vitamin supplements in preventing miscarriage?
Bottom line: 
Taking any vitamin supplements prior to pregnancy or in early pregnancy (less than 20 weeks’ gestation) did not help prevent either early or late miscarriage or stillbirth. Providing women with vitamin A or multivitamin supplements, with or without folic acid, may increase the risk of a multiple birth, which may confer increases in perinatal morbidity and mortality. There was insufficient evidence to examine the effect of different combinations of vitamins on miscarriage, stillbirth and measures of infant growth. The vitamins given included vitamin A, alone or with iron, folic acid, zinc or multivitamins; vitamin C with or without multivitamins or vitamin E; folic acid with or without multivitamins and/or iron; multivitamins with iron and folic acid; and multivitamins alone.
Many of the trials included in the review were not of high quality, either due to poor or unclear allocation concealment, or large losses to follow-up, which increased the risk of bias in the results. The data were also complicated by differing definitions of miscarriage. Other studies did not specify their definition of miscarriage or stillbirth. No trials reported on any potential psychological effects, such as anxiety and depression.
Poor diet with insufficient vitamins has been associated with an increased risk of miscarriage in early pregnancy. This has prompted investigation of the use of vitamin supplements prior to pregnancy or in early pregnancy to reduce the risk of miscarriage.
Review CD#: 
April, 2011
Authored by: 
Brian R McAvoy