One of the most effective factors during pregnancy is nutrition. Multivitamins not only supply mothers’ nutrition needs but also affect the health of fetus. On the other hand, weight gain influence the normal health of both the mother and the fetus during the process of pregnancy. The present research intended to investigate the effect of multivitamins on the weight gain of pregnant women with singleton pregnancy, possessing different socio-economic status, as well as the effects of socio-economic factors on the same variable. To this end, 150 pregnant women were studied from week 17 through 37 referring to the Perinatology clinic of Emam Hospital in Sari. The participants were randomly divided into two groups. Then, the demographic data including personal and socio-economic information were recorded. Afterwards, one group was given multivitamin pills while the other group received placebo pills in a daily manner up to week 37. Accordingly, their weight gain was recorded and data were analysed using SAS statistical software. In order to compare the Mean of the aforementioned variables, t-student test and Least Square (LS) means were used. Generalized Linear Model (GLM) analysis method was used to investigate the effect of studied factors on the aforementioned variables. Furthermore, Pearson Correlation between the variables was calculated. According to the results, the weight gain of mothers in control and case (experimental) groups indexed 13.63 and 9.39 kilograms respectively during 20 weeks indicating that there was a statistically significant difference (PËÃ?â??Ã?â??0.05) between the groups. The results of Linear Model showed that none of the variables had any statistically significant effect on weight gain of pregnant mothers. However multivitamin consumption, fathers’occupation and salary were more effective variables. The Pearson Correlation between the variables was calculated showing that there was a statistically significant correlation between mothers’ BMI and weight gain. Consequently, weight gain during pregnancy, in mothers with normal BMI who took multivitamins, was less in comparison to the placebo group. It seems that multivitamins prevent abnormal weight gain in pregnant women by regulating energy and other nutrients metabolism.
