Supplementary Material for: Risk of Impending Preterm Delivery Associated with the Presence of Amniotic Fluid Sludge in Women in Preterm Labor with Intact Membranes

Objective: To determine the association of amniotic fluid sludge with impending preterm delivery in women in preterm labor with intact membranes. Methods: This was a retrospective cohort study in women at 22–34 weeks’ gestation in preterm labor with intact fetal membranes between February 2008 and May 2009. 16 women with amniotic sludge were identified. Each case of amniotic sludge was matched with 3 randomly selected controls. The primary outcome was delivery within 48 h of examination. Results: Mean cervical length was shorter in women with sludge than women without sludge (20.5 ± 9.0 vs. 27.9 ± 6.9 mm, p = 0.0016). There was a significant difference in the mean ultrasound-to-delivery interval in women with and without sludge (21.7 vs. 49.4 days, p = 0.006). Logistic regression analyses demonstrated that amniotic fluid sludge is a strong independent predictor of impending preterm delivery within 48 h (OR 11.2, 95% CI 1.2–125.9), 7 days (OR 3.8, 95% CI 1.2–17.3) and 14 days (OR 7.5, 95% CI 1.8–30.4). Conclusions: Amniotic fluid sludge on ultrasound scan is associated with impending preterm delivery in women in preterm labor with intact membranes.