Acute histologic chorioamnionitis at term: nearly always noninfectious

Area of Science:

• Obstetrics and Gynecology
• Perinatal Medicine
• Infectious Disease

Background:

• The association between histologic acute chorioamnionitis and infection is well-documented in preterm deliveries.
• However, this link is less understood in term pregnancies, where infection is less prevalent.

Purpose of the Study:

• To investigate the relationship between histologic acute chorioamnionitis and infection in low-risk, term pregnancies.
• To explore potential noninfectious causes and associated factors of histologic chorioamnionitis in this population.

Main Methods:

• Secondary analysis of 195 low-risk women with term pregnancies from a randomized trial.
• Placental evaluation included histologic scoring and comprehensive microbiologic analysis (cultures, PCR).
• Infection was defined by specific microbial load criteria; chorioamnionitis was graded (0, 1, or 2).

Main Results:

• Histologic chorioamnionitis (Grade 1 or 2) was found in 34% of placentas, but infection was only present in 4%.
• Histologic chorioamnionitis strongly correlated with intrapartum fever (69% vs. 26% in afebrile women, P<.0001), often associated with epidural use.
• Elevated inflammatory markers (IL-8, IL-6) and higher white blood cell counts were observed with increasing grades of chorioamnionitis.

Conclusions:

• Histologic chorioamnionitis in term pregnancies frequently stems from noninfectious inflammatory processes.
• The condition is significantly associated with maternal fever, likely linked to epidural analgesia.
• An activated maternal immune system at delivery admission is also associated with histologic chorioamnionitis.