Relationship between body mass index of third trimester of pregnancy and type of delivery

Maternal Body Mass Index (BMI) is considered as one of most effective determinant of delivery rout, by increase in this index, risk factor of cesarean section enhanced. Based on high prevalence of obesity in women, this study designed to assess the relationship between admission BMI and type of delivery. Five hundred and forty pregnant women in third trimester of pregnancy (≥37weeks) were studied within 1 year (from June 2012 to June 2013), at Sayad Shirazi Referral Hospital, Gorgan, Iran, through a analytic cross-sectional study. BMI was calculated for each mother at the time of labor admission. Height and weight were measured, and were categorized into 3 groups according to their BMI which included of underweight and normal (BMI<25), overweight (BMI=25-29.9) and obese (BMI≥30). And in each group route of delivery (cesarean or natural delivery) were assessed. Pregnant women with the previous cesarean delivery, history of diabetes type 1, 2 or gestational diabetes, hypertension, twin pregnancy and unwilling to participate in study were excluded from study. Mean of age and mean of gestational age were 25.8±5.4 years and 38.2±2.6 week, respectively. 50.6% of mothers were undergone cesarean delivery and there was a significant relationship between BMI and type of delivery (P<0.0001). For each unit increase in BMI, risk of cesarean section rose 1.08 times (CI95%=1.04-1.13, P<0.0001) and the risk of cesarean delivery in obese pregnant women was 2.8 (CI95%=1.7-4.4, P<0.0001) times higher than those with underweight and normal weight. There is a significant relationship between maternal BMI at the time of labor admission and type of delivery and increasing of BMI is associated with increasing of cesarean section rate. Thus, keeping the BMI in normal range during pregnancy is suggested to pregnant women to reduce the pregnancy complications.