Causes of Postpartum Endometritis

Postpartum endometritis is a bacterial infection of the uterine lining that occurs within six weeks following childbirth. It represents the most common infectious complication after delivery—particularly after cesarean section, where incidence rates may reach 10–20%, compared with 1–3% after vaginal birth.

The primary etiologic agents are polymicrobial, typically involving a mixture of aerobic and anaerobic organisms. Common pathogens include *Escherichia coli*, *Streptococcus species* (especially *S. agalactiae*), *Enterococcus faecalis*, *Bacteroides fragilis*, and *Prevotella* spp. These microbes often originate from the lower genital tract or gastrointestinal flora and ascend into the uterus during labor, membrane rupture, or instrumentation.

Risk factors significantly increase susceptibility. Prolonged rupture of membranes (>18 hours), prolonged second stage of labor, multiple vaginal examinations during labor, chorioamnionitis, retained placental fragments, and cesarean delivery—especially if performed emergently or without appropriate antibiotic prophylaxis—are well-documented contributors. Maternal comorbidities such as obesity, diabetes, immunosuppression, or bacterial vaginosis further elevate risk.

Pathogenesis involves breach of normal anatomical and immunological defenses: cervical dilation, trauma to the endometrium during delivery, and postpartum uterine involution create an environment conducive to microbial colonization and biofilm formation. Impaired local immune surveillance—due to hormonal shifts and postpartum immune modulation—also facilitates infection establishment.

Clinical presentation typically includes fever (>38.0°C), uterine tenderness, foul-smelling lochia, tachycardia, and leukocytosis. Delayed diagnosis or inadequate treatment may lead to serious sequelae, including pelvic abscess, sepsis, thrombophlebitis (notably ovarian vein thrombosis), and, rarely, chronic pelvic pain or infertility.