Prenatal multivitamin supplementation increases birth weight

Background: The aim of this study is to examine whether there is any positive impact of prenatal iron and vitamin supplementation on birth weight, and if this practice could be a cause of macrosomia. Methods: A total of 1,838 term pregnant women were included in this study and were divided into four groups: iron group (women having only iron supplementation), vitamin (women using only multivitamins), vitamin+iron (women using both iron and multivitamin preparations), and control group (women having neither iron nor vitamin supplements). Statistical analysis was performed to compare age, gravida, parity, hemoglobin, BMI and birth weight. Groups were compared in terms of macrosomia and correlation analysis carried out between demographics and birth weight. Results: The birth weight was significantly higher in the vitamin group and the vitamin+iron group than in the iron group and the control group. Vitamin supplementation increased the risk of macrosomia 3.9 times, while vitamin+iron usage increased the risk 4.8 times. Conclusions: Uncontrolled use of multivitamins and/or iron supplements may increase tendency for fetal macrosomia. The use of multivitamins and/or iron supplements by pregnant women must take into account maternal age, maternal diet and maternal BMI. Our findings support a reduction in the unnecessary use of vitamin and iron supplements in pregnancy, and a reversal of the trend to start vitamin and iron supplementation without any control. The increasing prevalence of obesity and excessive weight in pregnant women should be a warning against the uncontrolled usage of vitamins and iron during pregnancy.