Obesity increases the risk of pregnancy complications, including puerperal infections and cesarean delivery, and risk rises with increasing body mass index (BMI). Since obese women are more likely to have comorbidities that would necessitate delivery prior to their due date (i.e. prior to 40 weeks gestation), and class III obesity specifically is an indication for delivery by 39 weeks, these patients have a high rate of labor induction. In nulliparous women from the general population (obese and non-obese), labor induction at 39 weeks (compared to expectant management) is associated with less maternal morbidity and a lower cesarean rate. Researchers previously conducted a pilot randomized placebo-controlled trial in obese, nulliparous women undergoing labor induction at term and found that the cesarean delivery rate was lower in women who received a prophylactic antibiotic regimen during labor compared with those who received the placebo. Researchers proposed multi-center trial aims to test this hypothesis in a large sample with adequate power to determine whether prophylactic antibiotics during labor are associated with a decrease in the rate of cesarean delivery in term, nulliparous, obese women. If the findings from the pilot trial are confirmed, this would represent a novel intervention to decrease the cesarean delivery rate in a subset of women at highest risk for cesarean-related complications.

This is a multi-center randomized placebo-controlled trial in which nulliparous women with obesity who are undergoing induction of labor at term and not receiving IAP for GBS will be recruited (n=787). The participants will be randomized 1:1 to receive either prophylactic antibiotics during their labor induction (azithromycin 500 milligrams intravenously once and cefazolin 2 grams intravenously every 8 hours for up to three doses) or like-appearing placebos. The participants and their obstetrical providers will be blinded to the study intervention. The study will be conducted with an identical protocol at six study sites. Trained research nurses/assistants at each study site will consent and enroll participants, collect biospecimens, and collect demographic information and data on pregnancy and neonatal outcomes, and will convey this data to the primary site for analysis.

Researchers hypothesize that the group that receives the study drug regimen of prophylactic antibiotics during induction of labor will have a lower rate of cesarean delivery than the group that receives the placebo. They also hypothesize that the group that receives the study drug regimen will have a lower rate of puerperal infection than the placebo group.

Nulliparous women with obesity who are undergoing induction of labor at term will be eligible for participation in the study. Across all sites, 787 total subjects will be recruited.

Inclusion Criteria:

• BMI ≥30
• No prior deliveries at or beyond 20 weeks gestation
• Undergoing induction of labor
• Gestational age 37 weeks or more
• Age 15-45
• Not receiving IAP for GBS prophylaxis

Exclusion Criteria:

• Fetal death prior to labor induction
• Known fetal anomaly
• Multiple gestation
• Ruptured membranes for more than 12 hours
• Chorioamnionitis or other infection requiring antibiotics at the start of the labor induction
• Previous myometrial surgery
• Allergy to azithromycin or beta-lactam antibiotics

All subjects in this study will be pregnant women and fetus/infant dyads

Study participants, clinical personnel, and members of the research team responsible for collecting clinical outcomes will be blinded to the treatment group allocation. The research pharmacist at each site and the research analyst generating the randomization scheme will be the only study team members to know the treatment group allocation.