SCOTTSDALE, ARIZ. — The more obese a woman is before becoming pregnant, the lower her chances will be for successful induction of labor, according to researchers who reviewed computerized records of 45,998 pregnancies in a German database.
Dr. Rabbie Hanna and his colleagues reported the rate of successful induction fell from a high of 79% for women of normal weight with a body mass index (BMI) below 25 kg/m
“We saw that as obesity increases, normal labor decreases and induction of labor increases,” Dr. Hanna said in an interview at the annual meeting of the Central Association of Obstetricians and Gynecologists, where he presented the data in a poster.
The study mined a perinatal database of 170,258 cases collected from 1991 to 1997 in the state of Schleswig-Holstein. The investigators selected nulliparous, low-risk women who came to full term with singleton pregnancies. Prepregnancy height and weight had to be in the database for a woman to be included in the analysis.
Among the 45,998 pregnancies that fit these criteria, there were 898 (2%) pregnancies that ended in elective cesarean section and 45,100 (98%) in which the women underwent labor. In this latter group, 6,427 (14%) required induction of labor.
Dr. Hanna and his colleagues also reported that the proportion of women choosing cesarean delivery increased with BMI. The rate of elective cesarean delivery rose from 1.7% of women with normal weight to 6.1% of women who were morbidly obese. Elective cesarean rates were 2.5% in overweight women, 2.9% in those with class I obesity, and 4.9% in those with class II obesity.
The investigators didn't address whether trying to induce labor over two or three days is worthwhile in a morbidly obese patient. “We can't answer that question. She still has a 50–50 chance,” said Dr. Hanna, noting that cesarean delivery is associated with increased risk of complications.