Objective: To evaluate the relationship between gestational weight gain and pre-pregnancy body mass index (BMI) on the risk of adverse obstetric and neonatal outcomes using cut off BMI criteria by Regional Office for the Western Pacific Region of WHO (WPRO).

Materials and Methods: The present study was a retrospective cohort. Subjects of live birth singletons who had full term delivered at four tertiary care centers, teaching university hospitals between January and December 2012 were enrolled. All pregnant women with pre-pregnancy BMI 18.5 kg/m2 or over were recruited and categorized into two groups, normal BMI and high BMI. The level of BMI at 18.5 to 22.9 kg/m2 was defined as normal BMI, and level at or over 23 kg/m2 was defined as high BMI, respectively. Gestational weight gain (GWG) was grouped into two categories as recommended weight gain (RWG) and excessive weight gain (EWG) which defined as 11.5 to 16 kg and above 16 kg in normal pre-pregnancy BMI and 5 to 9 kg and above 9 kg in high prepregnancy BMI, respectively. The association between RWG and EWG in different pre-pregnancy BMI groups and poor adverse pregnancy outcomes were evaluated.

Results: Two thousand seven hundred and thirty-three pregnant women were recruited. Normal and high pre-pregnancy BMI women were 1,840 (67.33%) and 893 (32.67%), respectively. Of these, 2,036 cases had complete data for evaluation. In normal prepregnancy BMI, 737 (59.58%) were categorized as RWG (11.5 to 16 kg) and 500 (40.42%) as EWG (>16 kg), while in high prepregnancy BMI, 273 (34.17%) were categorized as RWG (5 to 9 kg) and 526 (65.83%) as EWG (>9 kg). The mean weight gain in the normal pre-pregnancy BMI group was 13.80+1.35 kg vs. 20.39+3.84 kg in the RWG and EWG group, respectively. While the mean weight gain in high pre-pregnancy BMI group was 7.32+1.38 kg vs. 15.24+4.46 kg in the RWG and EWG group, respectively. In
multivariate logistic analysis, normal pre-pregnancy BMI group with EWG had increased risk of instrumental delivery or cesarean section (Odd ratio; with OR 1.06, 95% CI 1.03 to 1.08, p<0.001) and high pre-pregnancy BMI group with EWG, there was significant\ increased risk of preeclampsia with birth weight above 90th centile (OR 1.09, 95% CI 1.04 to 1.15 and OR 1.09, 95% CI 1.06 to 1.12 with p = 0.001 and <0.001, respectively).

Conclusion: For pregnant women with high pre-pregnancy BMI by WPRO criteria increased the risk of pregnancy complications
and adverse pregnancy outcomes especially in excessive weight gain women. The high pre-pregnancy BMI should be a concern for pre-conception counseling. Optimal GWG ranges should develop based on pre-pregnancy BMI cut off for Asian women.

Keywords: Neonatal birth weight, Gestational weight gain, Pre-pregnancy BMI, WPRO