Chorioamnionitis: Intra-Amniotic Infection

Chorioamnionitis is an acute infection of the amniotic fluid, membranes, placenta, and/or decidua, most commonly caused by ascending polymicrobial bacteria from the lower genital tract (Ureaplasma urealyticum, Mycoplasma hominis, GBS, E. coli, anaerobes). Prolonged rupture of membranes allows bacterial colonization of the amniotic cavity. The inflammatory response involves neutrophil infiltration of the chorion and amnion, release of pro-inflammatory cytokines (IL-1, IL-6, TNF-α), and prostaglandin production that stimulates uterine contractions. Fetal exposure causes fetal inflammatory response syndrome (FIRS) with risks of neonatal sepsis, pneumonia, and neurodevelopmental injury.