THE RELATION BETWEEN BODY MASS INDEX AND INCIDENCE OF DELIVERY OUT OF DUE DATE IS DISCREPANT: AN OBSERVATIONAL STUDY
Wagdy M Amer
Department of Obstetrics & Gynecology, Faculty of Medicine, Benha University
Objectives: To evaluate the impact of body mass index (BMI) on the timing of labor in relation to the due date of delivery. Patients & Methods: 553 women were evaluated for baseline BMI and classified according to WHO classification. At the time of delivery, BMI was re-evaluated and excess BMI gain was determined. Time of delivery in relation to the due date of delivery and the incidence of preterm delivery (PTD) and postdate delivery (PDD) were determined. The relation between time of delivery and at-booking BMI was studied and Kaplan-Meier regression analysis was used to determine the cumulative risk of PTD and PDD at various values of BMI. Results: 35 parturient (6.33%) had PTD with mean gestational age (GA) of 239.8±8.65 days and 20 parturient had PDD at GA of 296.5±1.55 days. Eighteen under and average weights parturient had PTD, while 17 overweight-to-obese II parturient had PTD. PDD was prevalent among overweight-to-obese II parturient. There was a significant correlation between at-booking BMI and incidence of PTD and PDD and Kaplan-Meier regression analysis showed a progressive increase of PTD risk with increased at-booking BMI and risk was 40% for women with BMI of 35 kg/m2 and 80% for women with BMI >35 kg/m2. Also, the risk of PDD was 100% in women with a BMI of >35 but <36 kg/m2, and rise to 140% at BMI higher than 36 kg/m2. Conclusion: Preconception or at time of pregnancy diagnosis BMI strongly influences the time of delivery in relation to the due time. Extremes of BMI are associated with a high prevalence of PTD, while obesity is associated with PDD. BMI higher than 30 kg/m2 is associated with a high cumulative risk of delivery out of the due time and this risk multiplies extensively with each increase of BMI by 1 kg/m2.