Picture of the Month What is amniotic fluid ‘ sludge ’ ?

The presence of free-floating hyperechogenic material within the amniotic fluid in close proximity to the uterine cervix (Figures 1 (cover) and 2 and Videoclips S1 and S2) has been described previously in women with an episode of preterm labor1, in women with a history of preterm delivery or threatened preterm labor2, and in asymptomatic women at risk for spontaneous preterm delivery in the mid-trimester of pregnancy3. We have proposed the term amniotic fluid ‘sludge’ to refer to this sonographic finding and provided evidence that ‘sludge’ is an independent risk factor for impending preterm delivery, histological chorioamnionitis and microbial invasion of the amniotic cavity in patients with spontaneous preterm labor and intact membranes1. Moreover, amniotic fluid ‘sludge’ has been identified in asymptomatic women at risk for spontaneous preterm delivery in the mid-trimester of pregnancy and is also an independent risk factor for preterm prelabor rupture of membranes (PROM) and spontaneous preterm delivery3. To determine the nature of amniotic fluid ‘sludge’, the material collected under sonographic guidance was examined under the microscope and microbiological studies were performed.