The impact of increasing obesity class on obstetrical outcomes.

OBJECTIVE: Nationally, rates of obesity continue to rise, resulting in increased health concerns for women of reproductive age. Identifying the impact of maternal obesity on obstetrical outcomes is important to enhance patient care.

METHODS: We conducted a retrospective cohort study of 6674 women who delivered a singleton infant at ≥ 20 weeks' gestation between December 1, 2007, and March 31, 2010, at The Ottawa Hospital. Maternal pre-pregnancy BMI was used to classify women into normal, overweight, and obese (class I/II/III) categories according to WHO classifications. Obstetrical outcomes among obese women were compared with those of women with normal BMI. Multivariable regression models were used to determine adjusted odds ratios and 95% confidence intervals.

RESULTS: Compared with women with normal BMI, obese women had significantly higher rates of preeclampsia, gestational hypertension, and gestational diabetes, and these rates increased with increasing BMI (trend-test P < 0.001). There was a significant increase in rates of induction of labour in the obesity categories, from 25.3% in women with normal BMI to 42.9% in women with class III morbid obesity (aOR 1.67; 95% CI 1.43 to 1.93). Rates of primary Caesarean section rose with increasing BMI and were highest in women with class III morbid obesity (36.2% vs. 22.1% in women with normal BMI) (aOR 1.46; 95% CI 1.23 to 1.73).

CONCLUSION: Increasing BMI is associated with increasing rates of preeclampsia, gestational hypertension, and gestational diabetes. There is a significant increase in rates of induction of labour with increasing obesity class, and a significantly increased Caesarean section rate with higher BMI. Obstetrical care providers should counsel obese patients about the risks they face and the importance of weight loss before pregnancy.