[Relations between pre-pregnancy body mass index, gestational weight gain, and the occurrence of neonatal asphyxia].

Objective: To assess the relationship between pre-pregnancy body mass index (BMI), weight gain during pregnancy, and the risk of neonatal asphyxia.

Methods: Data was collected in 6 countiedeities covered by Peri-natal Health Care Surveillance System which was part of a Sino-American cooperative project on neural tube defects prevention established in 1992. The study population consisted of 83,030 women who attended premarital/preconception medical physical examination program and had delivered single live birth with at least 20 gestational weeks from 1995 to 2000 in Jiaxing area, Zhejiang province.

Results: from the Chi-square test were employed to test the differences in the rates of neonatal asphyxia between groups with different BMI and other characteristics. Multivariate logistic regression method was conducted to examine the association between pre-pregnancy BMI, gestational weight gain, and the risk of asphyxia. Results The average rate of neonatal asphyxia was 11.3% (95% CI: 11.1%-11.6%). The rates of neonatal asphyxia among women with BMI < 18.5 kg/m2, 18.5-22.9 kg/m2, 23.0-24.9 kg/m2, and > or = 25.0 kg/m2 were 11.0% (95% CI: 10.5%-11.5%), 11.3% (95% CI: 11.1%- 11.6%), 11.8% (95% CI: 11.0%-12.6%), and 12.9% (95% CI: 11.6%-14.4%) respectively. The rates of neonatal asphyxia were 12.4% among women with weight gain < 0.3 kg/wk, higher than women with higher weight gain. After adjusting for residential area, maternal age, educational level, occupation, parity, times of prenatal visit, high-risk experiences during pregnancy, high-risk experiences at time of delivery, gestational week and birth weight, the estimated ORs were 1.03 (95% CI: 0.97-1.09), 1.06 (95% CI: 0.96-1.16) and 1.14 (95% CI: 1.00-1.31), respectively. These ORs became 1.02 (95% CI: 0.95-1.09), 1.01 (95% CI:0.90-1.13) and 1.08 (95% CI: 0.92-1.28) after further adjusting the variable "gestational weight gain". The estimated ORs for neonatal asphyxia were 1.06 (95% CI: 1.01-1.12) for women with weight gain at 0.3-kg/wk and 1.09 (95% CI: 1.02-1.20) for women with weight gain <0.3 kg/wk when compared to those with weight gain > or = 0.5 kg/wk.

Conclusion: Lower weight gain seemed to have the effect of increasing the risk of neonatal asphyxia.