Background: Amniotic fluid sludge (AFS) has been demonstrated in cases of intrauterine infection, one of the causes of preterm labor. Therefore, AFS is used as a predictor of preterm labor.

Objective: To determine prevalence of AFS in low-risk pregnant women and diagnostic performance of AFS for screening of preterm delivery in low-risk cases of preterm delivery.

Materials and Methods: Prospective descriptive study was conducted in low-risk pregnant women of preterm delivery who attended the antenatal care clinic in Rajavithi Hospital at gestational age (GA) 16 to 24 weeks between May 1, 2016 and October 31, 2017. All subjects were examined by transvaginal ultrasound to demonstrate AFS and then followed until delivery.

Results: Prevalence of AFS in all cases was 72/330 cases (21.8%). Premature delivery occurred in AFS positive and AFS negative were 3/72 (4.2%) and 22/258 (8.5%), respectively. Baseline characteristics were similar except mean BMI, and type of contraception. Mean GA at delivery was the only significant different obstetrical outcome. Diagnostic performances of AFS for screening low risk pregnant women for spontaneous preterm delivery less than 37 weeks of gestation had sensitivity of 12.0%, specificity of 77.4%, accuracy of 77.4%, positive predictive value of 4.2% and negative predictive value of 91.5%.

Conclusion: Prevalence of AFS in low-risk pregnant women of preterm delivery was 21.8%. AFS is not sensitive for screening of preterm delivery in low-risk cases.

Keywords: Amniotic fluid sludge, Preterm labor, Pregnancy