Midtrimester Intra-Amniotic Sludge and the Risk of Spontaneous Preterm Birth

We examined the association between midtrimester intra-amniotic sludge and spontaneous preterm birth (PTB) in asymptomatic women undergoing amniocentesis. We performed a prospective cohort study of women having an amniocentesis for fetal karyotyping between 14 and 24 weeks' gestation. Cervical length and the presence of amniotic sludge were assessed by transvaginal ultrasound. Amniotic fluid concentrations of matrix metalloproteinase-8, glucose and lactate were measured. Early (< 32 weeks) and late (32 to 36 weeks) preterm premature rupture of membranes (PPROM) and spontaneous PTB constituted primary outcomes. Nonparametric analyses were conducted. Three hundred ten women, including 94 (30%) with free-floating echogenic particles and 16 (5%) with dense amniotic sludge, were recruited. Dense amniotic sludge was linked with early (13%) but not with late (0%) primary outcome (p < 0.01). Two women with combined dense amniotic sludge and short cervix delivered 4 and 10 weeks later (at 20 and 25 weeks, respectively) and had a higher median amniotic lactate concentration than controls (p < 0.05). A third woman with dense amniotic sludge at 15 weeks was diagnosed with a short cervix and an intra-amniotic infection at 22 weeks that was eradicated with intravenous antibiotics. Midtrimester dense amniotic sludge is associated with early PPROM and spontaneous PTB.