To Örebro University

Objective: The aim of the present study was to assess the impact of different maternal Body Mass Index (BMI) classes on the risk of postpartum endometritis, wound infection, and breast abscess after different modes of delivery. Secondly to estimate how the risk of postpartum infection varies with different maternal BMI groups after induction of labor and after obstetric anal sphincter injuries.

Methods: A population-based observational study including women who gave birth during eight years (N = 841,780). Data were collected from three Swedish Medical Health Registers, the Swedish Medical Birth Register, the Swedish National Patient Register, and the Swedish Prescribed Drug Register. Outcomes were defined by ICD-10 codes given within eight weeks postpartum. The reference population was uninfected women. Odds ratios were determined using Mantel-Haenszel technique. Year of delivery, maternal age, parity and smoking in early pregnancy were considered as confounders.

Results: There was a dose-dependent relationship between an increasing maternal BMI and a higher risk for postpartum infections. Women in obesity class II and III had an increased risk for endometritis after normal vaginal delivery aOR 1.45 (95% CI: 1.29-1.63) and for wound infections after cesarean section aOR 3.83 (95% CI: 3.39-4.32). There was no difference in how maternal BMI affected the association between cesarean section and wound infection, regardless of whether it was planned or emergent. Women in obesity class II and III had a lower risk of breast abscess compared with normal-weight women, aOR 0.47 (95% CI: 0.38-0.58). The risk of endometritis after labor induction decreased with increasing maternal BMI. The risk of wound infection among women with an obstetrical sphincter injury decreased with increasing BMI.

Conclusion: This study provides new knowledge about the impact of maternal BMI on the risk of postpartum infections after different modes of delivery. There was no difference in how BMI affected the association between cesarean section and wound infections, regardless of whether it was a planned cesarean section or an emergency cesarean section.