[Association and interaction of pre-pregnant body mass index and gestational weight gain of women on neonatal birthweight].

To investigate the association between maternal pre-pregnant body mass index and gestational weight gain, as well as their interaction on neonatal birthweight. We built a cohort in Anqing Municipal Hospital from January 2014 to March 2015, enrolling pregnant women who decided to give birth in this hospital. All women were asked to fill a questionnaire for basic information collection. Medical information of both pregnant women and their newborns were obtained through electronic medical record. Chi-square analysis, multinomial logistic regression, multiplicative and additive interaction methods were used to analyze the association between pre-pregnant body mass index and gestational weight gain as well as their interactions on birth weight of the neonates. A total of 2 881 pregnant women were included in this study. Of the 2 881 newborns, 359 (12.46) were small for gestational age (SGA) and 273 (9.48) were large for gestational age (LGA). After adjusting the possible confounding factors, results from the multinomial logistic regression showed that pre-pregnancy underweight women were more possible to deliver SGA (a=1.33, 95: 1.02-1.73). If the gestational weight gain was below the recommended criteria, the risk of SGA (a=1.64, 95: 1.23-2.19) might increase. Pre-pregnancy overweight/obese could increase the risk of being LGA (a=1.86, 95: 1.33-2.60). Maternal gestational weight gain above the recommendation level was associated with higher rates of LGA (a=2.03, 95: 1.49-2.78). Results from the interaction analysis showed that there appeared no significant interaction between pre-pregnancy BMI and gestational weight on birthweight. Pre-pregnancy body mass index and gestational weight gain were independently associated with neonatal birthweight while pre-pregnancy BMI and gestational weight gain did not present interaction on birthweight.