[Relationship between the risk of emergency cesarean section for nullipara with the prepregnancy body mass index or...

Objective: To investigate the risk of emergency cesarean section during labor with the pre-pregnancy body mass index or gestational weight gain. Methods: A total of 6 908 healthy nullipara with singleton pregnancy and cephalic presentation who was in term labor in Beijing Obstetrics and Gynecology Hospital from August 1(st), 2014 to September 30(th), 2015 were recruited. They were divided into two groups, the vaginal delivery group (92.88%, 6 416/6 908) and the emergency cesarean section group (7.12%, 492/6 908). According to WHO body mass index (BMI) classification criteria and the pre-pregnancy BMI, the 6 908 women were divided into three groups, the underweight group(BMI<18.5 kg/m(2); 17.39%, 1 201/6 908), the normal weight group(18.5-24.9 kg/m(2); 73.00%, 5 043/6 908), the overweight and obese group (≥ 25.0 kg/m(2); 9.61%, 664/6 908). According to the guidelines of Institute of Medicine (IOM) , they were divided into three groups, the inadequate gestational weight gain (GWG) group (16.72%, 1 155/6 908), the appropriate GWG group (43.11%, 2 978/6 908), the excessive GWG group (40.17%, 2 775/6 908). Unadjusted and adjusted odds ratio (OR) and confidence interval (CI) of the risk of emergency cesarean section were calculated by bivariate logistic regression. Results: (1) Comparing to the vaginal delivery group, women in the emergency cesarean section group were older, with a lower education level. Their prepregnancy BMI was higer and had more gestational weight gain. They had higher morbidity of pregnancy induced hypertension and gestational diabetes mellitus. Comparing to the vaginal delivery group, the neonates in the emergency cesarean section group were elder in gestational week, with higher birth weight. More male infants and large for gestation age infants were seen in the emergency cesarean section group (all P<0.05) . (2) Overweight and obesity were associated with the increased risk of emergency cesarean section for nullipara, with the unadjusted OR of 1.98 (95%CI: 1.54-2.54), adjusted OR (aOR) of 1.66 (95%CI: 1.27-2.16). In the inadequate GWG group and the excessive GWG group, overweight and obese women had increased risk of emergency cesarean section, with adjusted OR of 2.33 (95%CI: 1.06-5.14) and 1.62 (95%CI: 1.44-2.28), respectively. In the appropriate GWG group, there was no significant difference in the risk of emergency cesarean section between the overweight and obese women and the normal weight women, with aOR of 1.54 (95%CI: 0.94-2.54). The underweight group was associated with decreased risk of emergency cesarean section (OR=0.55, 95%CI: 0.40-0.74; aOR=0.66, 95%CI: 0.48-0.90). While no significant difference in the risk of emergency cesarean section was found between the underweight women, the overweight and obese women, with the aOR of 0.31 (95%CI: 0.07-1.32), 0.73 (95%CI: 0.48-1.10), 0.66 (95%CI: 0.38-1.12), respectively. (3) Absolute value of gestational weight gain was associated with the increased risk of emergency cesarean section, (aOR=1.03, 95%CI: 1.01-1.05). GWG above IOM giudelines did not independently affect the risk of emergency cesarean section (OR=1.30, 95%CI: 1.07-1.58; aOR=1.01, 95%CI: 0.82-1.24). In the underweight group, the normal weight group and the overweight or obese group, the excessive GWG women and the appropriate GWG women had no significant difference in the risk of emergency cesarean section (aOR=1.03, 95%CI: 0.55-1.12; aOR=1.02, 95%CI: 0.80-1.30; aOR=1.03, 95%CI: 0.59-1.78) , respectively. GWG below IOM giudelines was associated with decreased risk of emergency cesarean section (OR=0.62, 95%CI: 0.45-0.85; aOR=0.64, 95%CI: 0.46-0.88). In the underweight group and the overweight or obese group, there was no significant difference in the emergency cesarean section risk between the inadequate GWG women and the appropriate GWG within women (aOR= 0.24, 95%CI: 0.06-1.01; aOR= 0.90, 95%CI: 0.40-2.04) . In the normal weight group, the inadequate GWG women had lower risk of emergency cesarean section (aOR=0.65, 95%CI: 0.45-0.95). Conclusions: Overweight and obese women have increased risk of emergency cesarean section. The prepregnancy BMI is supposed to be an appropriate level. Absolute value of gestational weight gain is associated with increased risk of emergency cesarean section. There is no correlation between the excessive GWG and the risk of emergency cesarean section.