Amniotic fluid sludge as a marker of intra-amniotic infection and histological chorioamnionitis in cervical insufficiency: a report of four cases and literature review.

Amniotic fluid sludge (AFS) is defined as the presence of particulate matter in the amniotic fluid in close proximity to the cervix. Although its prevalence is known to correlate with the risk of preterm delivery, initial reports describe a strong association between AFS and microbial invasion of the amniotic cavity (MIAC) and histological chorioamnionitis. However, AFS is also present in uncomplicated pregnancies, and its prevalence appears to increase with gestational age. Recent evidence debates the usefulness of AFS as a marker of early preterm delivery risk. We present four cases with AFS diagnosed by transvaginal ultrasound at admission for cervical insufficiency between 20 and 24 weeks of gestation, with confirmed lower genital tract and intra-amniotic infections by amniocentesis and histological chorioamnionitis and funisitis. Our findings reinforce the presence of AFS as a useful marker of MIAC, chorioamnionitis and funisitis that increase the likelihood of preterm delivery at an extreme gestational age.