Intra-Amniotic Sludge, Short Cervix, and Risk of Preterm Delivery

Objective: To evaluate the association between intra-amniotic sludge seen at cervical ultrasound and preterm delivery. Method: This retrospective study included women at high risk for preterm delivery who were referred for second trimester cervical length measurement by ultrasound between 18 and 32 weeks' gestation. Patients with multiple gestations, cerclage, or preterm labour were excluded. Ultrasound images were reviewed by two independent observers and divided into three groups: (1) no amniotic sludge, (2) light sludge, and (3) dense sludge in the amniotic fluid. The primary outcome measures were delivery within 14 days of examination and delivery before 34 weeks' gestation. Logistic regression analyses were performed to adjust for confounding factors. Results: Eighty-nine patients met the inclusion criteria. Mean gestational age at presentation was 25.8 +/- 4.4 weeks, and mean cervical length was 33 +/- 12 mm. The prevalence of light and dense amniotic fluid sludge was 10.1% and 5.6%, respectively. Delivery within 14 days of examination occurred in four (5.3%) women with no sludge, in two (22.2%) women with light sludge, and in three (60.0%) women with dense sludge (P < 0.01). Delivery before 34 weeks occurred in five (6.7%), four (44.4%) and four (80.0%) women, respectively (P < 0.01). Logistic regression analyses demonstrated that light amniotic fluid sludge, dense sludge, and cervical length of less than 25 mm were all significant and independent predictors of delivery within 14 days of examination and delivery prior to 34 weeks. Conclusion: The presence of amniotic fluid sludge is associated with delivery within 14 days and delivery before 34 weeks' gestation.