Influence of maternal body mass index on gestational weight gain and birth weight: A comparison of parity

Previous studies have revealed correlations among prepregnancy body mass index (BMI), gestational weight gain and the birth weight of the infant. However, as a variety of indices relating to the physique have been used to assess the optimal weight of pregnant women, no conclusions have yet been established regarding the Japanese population. Therefore, the aim of this study was to analyze the correlations among prepregnancy BMI, gestational weight gain and the birth weight of the infant in primiparous and multiparous females. The study was a retrospective analysis of pregnancy charts from a single birthing center from August 1998 to the end of September 2007. The subjects were primiparous (n=220) and multiparous (n=340) females, and the mean prepregnancy weights of the two groups were 52.8±8.8 and 54.3±9.0 kg, respectively. The mean prepregnancy BMI of the primiparous females was 20.8±3.1 kg/m2, compared with 21.6±3.5 kg/m2 for the multiparous females, and the mean birth weights of the infants were 3,153.0±364.1 g and 3,262.3±370.4 g for primiparous and multiparous females, respectively. When the correlation between the maternal factors and the birth weight of the infant was analyzed, the birth weight was revealed to be positively correlated with delivery weight and gestational weight gain in primiparous females. However, no correlations were observed between the birth weight of the infant and prepregnancy weight or BMI. In multiparous females, birth weight was revealed to be positively correlated with prepregnancy weight, BMI and the maternal delivery weight; however, no correlation was observed between the birth weight of the infant and gestational weight gain. The results of the present study also demonstrated that there were significant differences between the primiparous and multiparous females, with regard to gestational weight gain and weight reduction following delivery. The study indicated that the factors influencing birth weight may be different for primiparous and multiparous females.