Multivitamin use was associated with a 16% reduction in the risk of pre-term birth, and a 20% reduction in the risk of preterm labour, according to findings published in the American Journal of Clinical Nutrition.
The reported benefits were limited to normal weight women, and no benefits were observed in overweight women, report researchers from the University of Pittsburgh in the US and the University of Aarhus in Denmark.
“It may be that multivitamin use around the time of conception could be a safe and simple strategy to improve pregnancy outcomes, similar to folate supplementation,” wrote the researchers.
Caution
The authors said that their results should be “interpreted with caution” because multivitamin use is linked to other lifestyle factors.
“Because of current recommendations, it is unlikely that a randomized trial of peri-conceptional multivitamins is feasible,” they said.
“Therefore, methodologically rigorous prospective observational studies may be the only way to investigate if multivitamin supplementation around the time of conception may reduce risk of preterm births or small-for-gestational-age births.”
Study details
The researchers followed 35,897 women participating in the Danish National Birth Cohort. Multivitamin use was recorded during a 12 week period around the time of conception. Premature birth was defined as birth prior to the 37th week of pregnancy.
Results showed that normal weight regular users of multivitamins – defined as using for four to six weeks around the period of conception – had significantly reduced risks of preterm birth and labour.
Multivitamin use was also associated with a 17% reduction in the risk of giving birth to underweight babies, relative to the gestation period.
“The dominant brand of multivitamin supplements reported in the Danish National Birth Cohort contained 200 micrograms of folic acid,” explained the researchers.
“Thus, folate may be involved in the multivitamin-small-for-gestational-age births association, but other micronutrients may be important in the association between periconceptional multivitamin use and pre-term birth.”
The authors also note that zinc, and vitamins C and E have previously been linked to the risk of pre-term birth, which may be related to the impact of oxidative stress on the placenta.
Source: American Journal of Clinical Nutrition
2011, Volume 94, Pages 906-912
“Periconceptional multivitamin use and risk of preterm or small-for-gestational-age births in the Danish National Birth Cohort”
Authors: J.M. Catov, L.M. Bodnar, J. Olsen, S. Olsen, E.A. Nohr