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.
Caveat:
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.
Context:
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.
Cochrane Systematic Review:
Rumbold A et al. Vitamin supplementation for preventing miscarriage.
Cochrane Reviews, 2011, Issue 1. Article No. CD004073.
DOI: 10.1002/14651858.CD004073.pub3.
This review contains 28 studies involving 62,669 participants and
64,210 pregnancies.
