The influence of increasing BMI in nulliparous women on pregnancy outcome

Objective

The aim of the study was to demonstrate the influence of BMI in pregnancy on rates of adverse pregnancy outcome in overweight nulliparous women.

Study design

The study was a retrospective review of data from the local hospital database held at the Jessop Wing of the Royal Hallamshire Hospital in Sheffield. We reviewed all nulliparous women with recorded BMI at booking between January 2001 and November 2008 who delivered singleton babies. All the women were stratified into five groups (underweight, normal, overweight, obese, and morbidly obese). The different BMI range groups were compared with the group of women with a normal BMI (20-25). SPSS v15 was used for statistical analysis.

Results

The caesarean section rate rose from 18.2% in women of normal BMI to 40.6% in the morbidly obese women (RR 2.2 - CI 1.7-2.8). Morbidly obese women had three times that risk of macrosomia compared with normal BMI women (RR 3.1 - CI 2.1-4.8). The stillbirth rate was associated with increasing obesity with RR 16.7 (CI 4.9-56) for the morbidly obese women.

Conclusions

Increasing degrees of obesity are associated with increases in the incidence of caesarean section, fetal birth weight and adverse pregnancy outcomes. The increased risk shows an increment in a stepwise fashion among the different BMI groups.