Supplementing women with any vitamins does not reduce the number of women who miscarry or have a stillbirth.
Poor diet, without enough vitamins, has been associated with an increased risk of women losing their baby in early pregnancy. Taking vitamin supplements prior to pregnancy or in early pregnancy may reduce the risk of miscarriage, but this review did not find this to be the case. However, women taking vitamin supplements before or at the time of conception may be more likely to have a multiple pregnancy. More research is needed to determine the impact of different combinations of vitamins. This review included 28 trials involving 96,674 women (98,267 pregnancies). —Cochrane Review