[Relations between pregestational body mass index, gestational weight gain and birth weight of neonates among women in the Southwest areas of China: A prospective cohort study].

Objective To explore the effects of both pre-gestational BMI and gestational weight gain (GWG) on the birth weight of neonates. Methods A total of 5 395 pregnant women were selected from the Southwest areas of China (Sichuan/Yunnan/Guizhou) and were divided into groups as pre-gestational underweight, normal weight, overweight and obesity, according to the WHO Recommendation on BMI Classification. Guidelines on Pregnancy weight were adopted from the Institute of Medicine to confirm the accuracy of GWG. Multinomial logistic regression model was used to assess the associations between pregestational BMI and GWG, on the birth weight of the neonates. Results After adjusting for related confounders, low pre-gestational BMI appeared as a risk factor for SGA (OR=1.91, 95%CI: 1.47-2.50), and was also associated with the decreased risk of LGA (OR=0.55, 95%CI: 0.47-0.66). Inadequate GWG was both associated with the increased risk of delivering SGA (OR=1.57, 95%CI: 1.21-2.03) and the decreased risk of LGA (OR=0.48, 95%CI: 0.41-0.57). Pre-gestational overweight/obesity (OR=1.85, 95%CI: 1.58-2.17) and excessive GWG (OR=1.87, 95%CI: 1.67- 2.11) were both positively associated with the risks on LGA. Data from the stratified analysis indicated that inadequate GWG was positively associated with the risk of SGA among underweight or normal weight women (all P<0.05), but not with those overweight/obese women. Conclusions Pre-gestational BMI and GWG were important influencing factors on the birth weight of neonates. Health education programs for pregnant women should be intensified and gestational weight gain should also be reasonably under control. Key words: Body mass index; Gestational weight gain; Neonate; Birth weight