Tipping the Weight Scales on Cesarean Odds

Cesarean risk affected by prepregnancy weight and weight gain in pregnancy

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Being obese before pregnancy increases the odds for high blood pressure, diabetes and premature births, but the effect of weight gained during pregnancy may change a mother's plans for delivery.

A recent study looked at the links between weight and cesarean births (surgical delivery of a baby) to see if weight changed the chance of having a cesarean delivery.

The researchers found that women who were obese before they became pregnant had a greater chance of having a cesarean birth. Even women who were underweight before they became pregnant, but gained a lot of weight when pregnant, had increased odds of a cesarean delivery.

"Discuss healthy weight gain during pregnancy with your obstetrician."

Lauren E. Graham, MSPH, from the Department of Public Health Sciences at the University of North Carolina in Charlotte, NC, was part of a team of researchers who conducted this study.

The study used data on 2,157 women from the 2008 to 2009 North Carolina Pregnancy Risk Assessment Monitoring System. The data was obtained two to six months after the women had delivered a baby.

Most of the women in the study were between 25 and 34 years old and about 58 percent were married and non-Hispanic white women.

Each woman’s method of delivery and body mass index (BMI) was obtained from North Carolina birth certificates. The researchers classified the BMI data into groups. A BMI of less than 18.5 was considered underweight. BMI within the normal weight range was 18.5 to 24.9. Overweight was considered a BMI from 25 to 29.9, and a BMI of 30 or greater was considered obese.

The researchers collected additional information on the women that included the amount of weight gained during their pregnancy. The researchers categorized the weight gain as too little for pre-pregnancy BMI (low), adequate for pre-pregnancy BMI (normal) or too much for pre-pregnancy BMI (high).

About half of the women had a normal pre-pregnancy BMI, 13 percent were underweight and 21 percent were overweight.

During pregnancy, about 40 percent of the women gained a high amount of weight and 33 percent gained a normal amount of weight.

Pre-pregnancy obesity was associated with a two-fold increased risk for cesarean delivery, compared to normal pre-pregnancy BMI. Overweight women had 17 percent increased odds of having a cesarean birth compared to women with normal pre-pregnancy BMI.

Compared to normal weight gain during pregnancy, high weight gain increased the odds of a cesarean birth by 41 percent.

When the researchers looked at the combination of pre-pregnancy weight and weight gained during pregnancy on cesarean delivery odds, they found increased odds in some women who were underweight before pregnancy.

Women who were underweight before pregnancy, but gained a normal or high amount of weight during their pregnancy, had 24 and  42 percent increased odds of having a cesarean delivery, respectively, compared to women who had a normal pre-pregnancy BMI and normal or high pregnancy weight gain.

Women who were obese before pregnancy and gained a normal or high amount of pregnancy weight had 71 and 64 percent increased odds of cesarean birth compared to women who were at normal weight before pregnancy and gained a normal or high amount of weight when pregnant.

The highest risks for cesarean delivery were found in women who were obese before pregnancy and had a low weight gain during pregnancy. This group of women had a 2.6-fold higher risk of a cesarean birth compared to women with a normal pre-pregnancy BMI who gained a low amount of weight during pregnancy.

The authors noted several limitations of their study, including that information on BMI at delivery and method of delivery were obtained from birth certificates and could have been inaccurate.

“Given the increases in both obesity and cesarean deliveries in the United States, understanding the BMI-cesarean delivery association is important. Health care practitioners may wish to stress the importance of achieving a healthy weight before pregnancy to reduce the risk of cesarean delivery and other adverse pregnancy outcomes,” the authors wrote.

The research was published in the March issue of Birth.

The authors did not disclose any conflicts of interest.

Review Date: 
March 26, 2014
Last Updated:
March 27, 2014