Study aims to reduce C-section rates in pregnant women with obesity

University of OklahomaNov 6 2024

Pregnant women with obesity face an increased risk of complications, including the need for a cesarean section, which carries its own set of risks. A University of Oklahoma physician-researcher recently earned a $3.1 million National Institutes of Health grant to lead a multicenter national clinical trial studying whether antibiotics given at the beginning of labor induction result in a decrease in C-sections. The trial is thought to be the first large-scale study of its kind in the United States.

Today, 40% of American women are obese when they become pregnant, and they have health problems that make them more likely to require delivery before their due date, typically at 39 weeks. Sometimes, a C-section is necessary, but it can cause other problems, such as wound infections and a higher risk of bleeding. Because labor inductions have increased along with the rise in obesity, we need a way to minimize C-sections so the mother can have the lowest risk for complications. We are conducting this study with first-time mothers with obesity because they have the highest risk for a C-section."

Stephanie Pierce, M.D., study principal investigator, OU Health maternal-fetal medicine specialist and associate professor in the OU College of Medicine

Pierce was awarded the grant after the success of her pilot study demonstrating that antibiotics given at the start of labor induction to first-time pregnant women with obesity resulted in a 27% lower C-section delivery rate. That study was published in the American Journal of Obstetrics and Gynecology MFM (Maternal-Fetal Medicine).

Pierce said that giving antibiotics during labor induction may decrease the level of inflammation in the mother's body. Obesity causes chronic inflammation (a prolonged, low-level immune response), and labor itself is an inflammatory state. Research shows that too much inflammation may cause dysfunction of the uterine muscle, which can cause abnormalities in the labor process. In addition, antibiotics may treat any infections that are not showing symptoms like fever but nonetheless are affecting the labor process.

Antibiotics are frequently prescribed to patients ahead of many types of surgery, including C-sections, but giving antibiotics to women at the start of labor induction (prophylactically) is a brand-new area of study. In the trial, half of the participants will be randomly assigned to receive the antibiotics azithromycin or cefazolin through an IV; the other half will receive an IV placebo.

While the overall aim of the study is to determine whether antibiotic prophylaxis leads to a decrease in C-sections, the research team will also analyze infection rates and complications in mother and baby 30 days after delivery. They will also collect umbilical cord and maternal blood samples for future investigations of the process by which antibiotics lower the probability of a C-section. In addition, the research team will collect stool samples from both mother and infant one month after delivery to investigate whether the antibiotics alter the mother or baby's microbiome, the trillions of microbes in the intestines that are important for normal body functions.

Collectively, the clinical trial aims to enroll nearly 800 pregnant women with obesity. The other participating institutions are Duke University, University of Alabama at Birmingham, University of Florida and MetroHealth Medical Center, which is associated with Case Western University in Cleveland. Enrollment will begin soon, and the study will last five years. As the overall principal investigator, Pierce will manage all aspects of the study.

"This is an exciting opportunity to develop a new intervention that can improve outcomes for pregnant women with obesity," Pierce said. "The issue of obesity has been challenging to obstetricians, and the average BMI during pregnancy is only increasing. It is very gratifying to be part of a team that is developing a solution that has the potential to decrease complications and improve the health of mother and baby alike."