'Super obese' parturients may account for higher C-section rates.(Obstetrics)

PALM DESERT, CALIF. -- There may be a threshold of morbid obesity associated with a sharply increased risk of nonelective cesarean delivery that is not shared by less obese women, according to results of a preliminary study presented at the annual meeting of the Society for Obstetric Anesthesiology and Perinatology.

The issue may have clinical implications for management of women at the lower ranges of morbid obesity who may wish to undergo labor without early and aggressive epidural management in anticipation of a probable cesarean section.

In their study, investigators at the University of Michigan, Ann Arbor, looked for a linear increase in cesarean deliveries as obesity increased, but instead found that nonelective cesarean deliveries did not significantly increase until body mass indexes rose above 46.

At the highest ranges of obesity, a very significant increase in nonelective C-sections was seen in the study of 226 parturients: 58% of those with a BMI of 47-88, compared with 39% for women with BMIs between 30 and 46.

Monica Riesner, M.D., of the department of anesthesiology at the University of Michigan, presented the findings on behalf of a colleague, Jill Mhyre, M.D., who could not attend the meeting.

Dr. Mhyre and associates studied the charts of obese parturients who delivered vaginally or by nonelective C-section at their institution between 1999 and 2002. Women undergoing elective C-sections were not included in the analysis.

Among the patients meeting study criteria, 62 had a BMI between 30 and 39.9 (defined as obese by the Institute of Medicine); 116 had a BMI between 40 and 49.9, and 48 had a BMI between 50 and 88. A BMI greater than 50 has been proposed by some authors to constitute a new category, the "super obese."