Do vitamin supplements increase the risk of early fetal death?

A new study from Denmark suggests that multivitamin use during the period from before conception to early pregnancy may be linked to a slightly higher risk of early fetal loss. Experts criticize the study for not proving a cause and effect relationship.

The observational study analyzed self-reported data from 35, 914 women on vitamin supplement use during a 12-week period from before conception to early pregnancy (periconceptional) and cases of fetal death (1). The data analysis indicated that women using multivitamins had a small increased risk of early (but not late) fetal death. The use of folate supplements alone was not associated with fetal death.

The researchers noted that further studies on preconceptional multivitamin use are needed to guide public health recommendations. Experts commented that the observed association does not allow one to come to valid conclusions. The study did not measure the nutritional status (e.g., blood concentrations of the single vitamins) of the participants. Earlier research found that women with low levels of folic acid had a 50% in- creased risk of losing their babies early in pregnancy (2, 3). In addition, having enough folic acid in the early months of pregnancy can reduce the risk of having a baby born with a serious birth defect of the brain or spine (4). Early fetal death is very common, occurring in 15% of pregnancies in the developed world.

1. Nohr E. A. et al. Periconceptional intake of vitamins and fetal death: a cohort study on multivitamins and folate. Int J Epidemiol. Published online January 2014.
   
2. Hovdenaka N. and Haram K. Influence of mineral and vitamin supplements on pregnancy outcome. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2012; 164(2):127-132.
   
3. Black R. E. Micronutrients in pregnancy. British Journal of Nutrition. 2001; 85(2):S193–S197.
   
4. Goh Y. J. et al. Prenatal multivitamin supplementation and rates of congenital anomalies: a meta-analysis. Journal of Obstetrics and Gynaecology Canada. 2006; 28:680–689.