Black women have the highest rates of obesity in this country
besity before pregnancy increases the likelihood that women with low-risk pregnancies and who haven’t previously had a cesarean section will deliver by C-section, according to a new study.
“The likelihood of a primary cesarean increased consistently across categories of obesity in a population of low-risk women who would otherwise be likely candidates for a vaginal birth, even after controlling for demographic and medical risk factors,” said lead author Eugene Declercq, professor of community health sciences at the Boston University School of Public Health.
The study, published online in the journal Birth, has the strongest evidence yet identifying pre-pregnancy obesity as an independent risk factor for cesarean delivery. The research team analyzed birth certificate data from 2012 for more than 2.2 million new mothers in 38 states who had not had prior cesareans. Overall, 46 percent of mothers were considered overweight (25 percent) or obese (21 percent).
Rates of cesareans were 1.6 to 2 times higher for obese women than for those of normal weight category, the study found, with higher rates among very obese women. The rate of cesareans for lower-risk women in the normal-weight range was 14.6 percent, according to the study. That increased to 22.9 percent for women in the lower obesity range, and 35.1 percent for women at the high end of the range. Among first-time mothers, more than two in five with pre-pregnancy obesity had C-sections.
Earlier research has shown a connection between obesity and C-sections, but several factors limited those studies, including reliance on survey samples or use of older data. Rates of both obesity and cesarean deliveries have increased in recent years. African-American women carry the largest burden of obesity in this country.
Researchers say there is no clear-cut reason why the primary cesarean rate would be higher in obese women, even when they controlled for maternal age, hypertension, and other medical and social risk factors. One possible reason could be that obese patients are monitored more closely because of a greater risk of stillbirth, which could trigger more interventions. Another reason is that labor management could be influenced by maternal weight, and practitioners may initiate surgery earlier on obese patients to avoid an emergency procedure or complication, though there are added risks associated with surgery in obese patients.
Declercq said that though the once-rapid growth of pre-pregnancy obesity in this country has slowed, “the consequences of having hundreds of thousands of United States mothers begin their pregnancy obese remains.” And while campaigns to prevent maternal obesity may be “challenging,” they are “necessary steps in mitigating the negative effects of obesity on maternal and infant health.”