Bigger Moms Run Bigger Risk of C-Sections
October 13, 1999 (Dallas) -- Larger women are more likely to need a cesarean delivery when they give birth, according to doctors at the Duke University Medical Center in Durham, N.C. Women hoping to deliver vaginally "should work with their obstetricians to set reasonable weight goals," says assistant professor of anesthesiology, Elizabeth A. Bell, MD.
Bell recommends that prior to labor, obese women have a epidural catheter inserted into the spine so they can receive regional anesthesia quickly should they need a C-section. "The catheter is a tube, like an IV," she tells WebMD. "We can administer light or strong medications through it, depending on what the woman needs." Most of the time "we use light drugs for labor so the mother can still move her legs and walk -- a 'walking epidural.' But with the epidural in place, if you need quick surgery, we can provide the appropriate anesthetic."
"In the past, anesthesia has been one of the leading causes of maternal mortality," Bell says. Pregnancy and obesity both make it difficult to breathe under general anesthesia, so a woman's risk is compounded when the two conditions are combined. The best remedy is to administer regional anesthesia so she can breathe on her own. This is best accomplished if the epidural catheter is in place, Bell explains. This form of anesthesia is extremely safe both for the mother and for the infant.
Bell and her colleagues studied the nearly 2,500 women who gave birth at the Duke University Medical Center in Durham, N.C., over a 16-month period. They calculated each woman's body mass index (BMI), a measurement of body fat calculated using a formula that is based on height and weight, and related it to her chances of having a C-section. Women requiring the surgery were an average weight of 191 pounds and had an average BMI of 53, while women who delivered vaginally weighed an average of 182 pounds and had an average BMI of 31. These differences are statistically significant. The researchers presented their results here at the annual meeting of the American Society of Anesthesiologists.
The researchers also found that the number of women who needed a C-section increased as BMI increased. Among women with a BMI of 20 or less (indicating a low amount of body fat), none had cesarean delivery. When BMI ranged from 21-30 (indicating a range of body fat from healthy to a heftier amount), the incidence was 0.3%, and when BMI was 31-40 (consistent with obesity), the incidence jumped to 31.6% -- a 100-fold difference.
Bell says she has preliminary data suggesting that the risk of cesarean delivery jumps even more markedly once a woman's BMI exceeds 40 -- the equivalent of being 5'5" and weighing 270-280 pounds.
Bell warns slimmer women not to be complacent about these findings. Noting that her group looked at BMI at delivery, she says, "Many women think pregnancy is a time when they can eat anything they want, and they put on a lot of weight. One message to these people is that how much you gain during pregnancy may affect your risk of a C-section, and there might be a consequence to that."