The effect of maternal and nutritional factors on birth weight: a cohort study in Tehran, Iran

Purpose This study aims to examine the effect of maternal food intake before and during pregnancy on birth weight. Design/methodology/approach As a prospective cohort study, a total of 585 pregnant women of first trimester, visiting Tehran Metropolitan Area public health centers and private sectors (clinics and hospitals), were interviewed at first phase, and pregestational dietary intake was obtained by a 168-item semiquantitative food frequency questionnaire. At the third trimester, dietary recalls were collected via interview. Finally, birth weight information was extracted from health records. Univariate and multivariate analysis was used to explore the effect of maternal and nutritional factors on birth weight. Findings The results of the analysis show that direct measures of nutrition, measured as food group consumption at first and third trimester of pregnancy, had no significant effect on birth weight once the confounding factors were controlled (p > 0.05). Of control variables included in the analysis, twin pregnancy outcome (p = 0.000), pregnancy number (p = 0.04), prepregnancy weight (p = 0.004) (marginally significant) and gestational age (p = 0.000) (marginally significant) were associated with birth weight. Originality/value The results of this study show no significant role of mother’s nutrition during pregnancy on birth weight, while long-term nutrition outcomes such as prepregnancy weight had significant role. It seems the main reasons behind less important role of pregnancy nutrition on birth weight in this study include the following: food intake deficiency is not a major problem for participants, and cross-sectional data on food intake are less important on outcome of pregnancy weight than long-term nutritional status outcome variables such as mother’s weight and height. This finding should be addressed in public health planning for women at childbearing age.