The increasing epidemic of obesity affects all areas of obstetrics. Obesity is associated with medical, surgical, and obstetrical complications and higher rates of induction dysfunctional labor patterns. Since one-third of all reproductive-aged women are obese and almost 10% are extremely obese, this represents a significant problem for obstetricians. Thus, researchers from the division of maternal fetal medicine in the department of obstetrics and gynecology at University of Cincinnati College of Medicine in Ohio conducted a study to better understand the association between failed induction and obesity as well as to determine if the link is correlated with increasing class of obesity.
To do this, the researchers conducted a population-based cohort deliveries study using the Ohio Department of Health’s birth certification database. The researchers sought to compare the rate of failed induction of labor between obese and normal weight women. For the purpose of the study, failed induction was defined as cesarean delivery after an attempted induction. Rates of neonatal morbidity (ie, assisted ventilation for more than 6 hours, neonatal transport to a tertiary care center, seizures, birth injury, and a 5-minute Apgar score < 7) were also assessed for normal versus obese women. Weight classes were stratified as underweight (Body Mass Index [BMI] < 18.5), normal (BMI between 18.5 and 24.9), overweight (BMI between 25 and 29.9), obesity class I (BMI is between 30 and 34.9), obesity class II (BMI is between 35 and 39.9), and obesity class III (BMI ≥ 40).
In this study, 12% of the women were in obesity class I, 7% were in obesity class II, and 5% were in obesity class III. Obese women were more likely to be older, from a low socioeconomic class, African American, and were more likely to have received infertility treatment. They were also more likely to have such medical complications as chronic hypertension and diabetes.
The researchers found that the rate of induction was associated with increased obesity class, with a 28% rate in women with normal weights and a 34% rate in women in the obesity class III group. They further found that failed induction was more likely in women who were obese as compared to the women with normal weights, with the rate of failure increasing with the obesity class. In looking at other factors, the researchers determined the most profound rate (80%) of failed induction occurred in women in obesity class III who did not have prior vaginal delivery and who had infants weighing more than 4500 grams.
Obesity was also associated with significantly increased neonatal morbidity. In comparison to those infants born to women with normal weights, infants born to women who were obese were more likely to have an Apgar score less than 7 at 5 minutes, require assisted ventilation, require use of antibiotics, and experience neonatal transfer.
“Our study demonstrates that obese women are twice as likely to fail an induction of labor as their normal weight counterparts,” the researchers explained. “Induction of labor, particularly in the obese population, should be undertaken when indicated only after counseling the women of the risk, benefits, alternatives and likelihood of achieving a vaginal delivery with an induction of labor.”
CDC: Maternal and Infant Health Research: Pregnancy ComplicationsObesity and Pregnancy: An Expert Interview
Addressing Maternal Obesity While Fostering Healthy HabitsObesity and Reproductive Disorders
Wolfe KB, Rocco RA, Warshak CR. The effect of maternal obesity on the rate of failed induction of labor. Am J Obstet Gynecol. 2011; Apr 8 [Epub].