Q&A: Impact of prophylactic antibiotics on cesarean rates for women with obesity
Key takeaways:
- Pilot study results showed prophylactic antibiotic use during labor induction reduced cesarean delivery for women with obesity.
- A larger study is underway to determine whether these results are significant.
Antibiotics given during labor induction for women with obesity may cut cesarean delivery rates by up to 27%, likely by decreasing inflammation, data from a small pilot study suggest. Researchers now aim to learn more in an expanded trial.
After the success of the pilot study, the NIH awarded a $3.1 million grant to Stephanie Pierce, MD, MS, to lead a larger trial evaluating the impact of prophylactic antibiotics at labor induction for women with obesity, who are at greater risk for obstetric complications. The trial is considered to be the first large-scale study of its kind in the United States.
“As physicians, we see the impact of obesity in our patients, and we have very few interventions, especially in obstetrics, that improve outcomes,” Pierce, maternal-fetal medicine specialist and associate professor at the University of Oklahoma College of Medicine, told Healio. “I encourage people to continue to ask these questions and continue to look for ways we can improve care for these patients. Rising obesity rates are a trend we are seeing in our country and in the world. We have a responsibility to our patients to treat in a way that improves their outcomes and health.”
For the pilot study, women who received the prophylactic antibiotics during induction had a 27% lower cesarean delivery rate compared with those who received placebo, which researchers noted may be due to antibiotics decreasing inflammation caused by obesity and labor. The data were published in the American Journal of Obstetrics & Gynecology MFM in 2022.
The upcoming study will be a larger, multicenter national clinical trial with the same aim as the pilot study and a goal of enrolling 800 pregnant women with obesity. Researchers also plan to evaluate infection rates and complications in mothers and infants 30 days postpartum and collect umbilical cord and maternal blood samples for future assessment. In addition, researchers will obtain stool samples from the mother and infant 1 month postpartum to investigate whether antibiotic use altered the microbiomes.
Healio spoke with Pierce about her past, current and future research and the potential clinical implications of the new study for physicians and pregnant patients.
Healio: What prompted you to begin your research in reducing cesarean section rates for women with obesity?
Pierce: We know that people with obesity have a higher risk for some pregnancy complications, and one of the biggest things we talk about is their risk for cesarean section. People who undergo a cesarean section have a higher risk for other complications like infection, postpartum hemorrhage, bleeding and wound infection. Those are all more common in people who have a cesarean section, regardless of their weight. People with obesity who have a cesarean section are at even higher risk for those complications. That is where the drive to find an intervention to decrease the cesarean section rate, particularly in this population, came from.
Also, for people with obesity and higher BMI, cesarean sections are generally more technically difficult. It is best for patients if we can figure out how to minimize or reduce the number of cesarean sections that we are performing in general, but especially in this population that is at high risk for other complications, too.
Healio: Could you summarize the findings from your previous pilot study?
Pierce: In our pilot study, we enrolled 168 nulliparous patients with a BMI of 30 kg/m2 or greater, and we conducted a randomized trial in which half of participants received placebo and the other half received prophylactic antibiotics during labor induction. They received azithromycin once through IV at the beginning of the labor induction, and then cefazolin every 8 hours for up to three doses during the labor induction.
We found in that study that the rate of cesarean section was lower for people who received antibiotics during labor induction compared with those who received placebo. Infection rate was similar between the two groups. But the study was not large enough to be powered for either of those outcomes to detect statistically significant differences. That is the reason we are conducting this larger, multicenter trial where we have statistical power and we can determine definitively whether the prophylactic antibiotics help to improve outcomes for these patients.
Healio: What are you hoping to observe in your upcoming larger study? How is it different from the pilot study?
Pierce: I hope that it shows improved outcomes. I hope that the intervention is associated with a lower rate of cesarean section and a lower rate of infection for these patients. During the pilot study, the absolute rate of infection was pretty low, so it is hard to tell a big difference between the two groups. With bigger numbers, we may be able to say more about their risk for infection, too. I’m hoping that with this larger study, if there is truly lower cesarean section rates among the people who receive antibiotics, then that could certainly have a lot of implications for our clinical practice and for how we manage these patients.
We are going to collect some samples, which we did not do in the pilot study, including maternal blood samples at enrollment to look at inflammatory markers and see if there are individual differences between patients going into induction. We are also going to collect stool samples from moms and infants to analyze whether giving the antibiotics during labor induction has any lasting effects on the gut microbiome, because one of the concerns with giving antibiotics is if it might have a harmful effect on the microbes that make up the gut biome, either for mom or for babies. We are hoping to begin enrollment in the spring of 2025.
Healio: What might be the clinical implications of these findings?
Pierce: There are many surgeries or even minor procedures that we perform as physicians where we give antibiotic prophylaxis. Labor induction is not one of those where we would typically give routine antibiotic prophylaxis. This study will tell us if we should be doing that for these patients with obesity and if it is helpful to improve their outcomes.
For more information:
Stephanie Pierce, MD, MS, can be reached at stephanie-pierce@ouhsc.edu.
References:
- Pierce SL, et al. Am J Obstet Gynecol MFM. 2022;doi:10.1016/j.ajogmf.2022.100681.
- Wilkerson A. OU leading first-of-its-kind national trial exploring potential of antibiotics for lowering C-section rates in women with obesity. OU News. www.ou.edu/news/articles/2024/november/ou-leads-study-exploring-antibiotics-for-lowering-c-setion-rates-in-women-with-obesity#:~:text=A%20University%20of%20Oklahoma%20physician,a%20decrease%20in%20C%2Dsections. Published Nov. 6, 2024. Accessed Nov. 15, 2024.