Clinical significance of the presence of amniotic fluid ‘sludge’ in asymptomatic high-risk patients for spontaneous preterm delivery

Objective—To determine the clinical significance of the presence of amniotic fluid (AF) ‘sludge’ among asymptomatic patients at high-risk for spontaneous preterm delivery. Study design—This retrospective case-control study included 281 patients with (n=66) and without (n=215) AF ‘sludge’, who underwent transvaginal ultrasound between 13 and 29 completed weeks of gestation. Patients with threatened preterm labor, multiple gestation, fetal anomalies, placenta previa, and uterine contractions were excluded. Results—The prevalence of AF ‘sludge’ in the study population was 23.5% (66/281). The rates of spontaneous preterm delivery at <28, <32, <35, and <37 weeks of gestation were 14.7% (29/197), 21.3% (46/216), 28.7% (62/216), and 42.1% (91/216), respectively. Patients with ‘sludge’ had: (1) a higher rate of spontaneous preterm delivery at <28 weeks [46.5% (20/43) vs. 5.8% (9/154), p<0.001], <32 weeks [55.6% (25/45) vs. 12.3% (21/171), p<0.001], and <35 weeks [62.2% (28/45) vs. 19.9% (34/171), p<0.001]; (2) a higher frequency of clinical chorioamnionitis [15.2% (10/66) vs. 5.1% (11/215), p=0.007], histologic chorioamnionitis [61.5% (40/65) vs. 28% (54/193), p<0.001] and funisitis [32.3% (21/65) vs. 19.2% (37/193), p=0.03]; (3) a higher frequency of preterm PROM [(39.4% (26/66) vs. 13.5% (29/215), p<0.001], lower gestational age at preterm PROM [24.7 weeks (22.3-28.1) vs. 32.3 weeks (27.7-34.8); p<0.001]; and (4) shorter ultrasound-to-delivery [‘sludge’ positive: 127 days (95% CI: 120-134) vs. ‘sludge’ negative: 161 days (95% CI: 153-169), p<0.001] and ultrasound-to-preterm PROM intervals [‘sludge’ positive: 23 days (95% CI: 7-39) vs. ‘sludge’ negative: 57 days (95% CI: 38-77), p=0.003] than those without ‘sludge’. AF ‘sludge’ was an independent explanatory variable for the occurrence of spontaneous preterm delivery at <28, <32, and <35 weeks, preterm PROM, MIAC, and histologic chorioamnionitis. Moreover, the combination of a cervical length <25 mm and ‘sludge’ confers an odds ratio of 14.8 and 9.9 for spontaneous preterm delivery at <28 and <32 weeks, respectively. Conclusions—AF ‘sludge’ is an independent risk factor for spontaneous preterm delivery, preterm PROM, MIAC, and histologic chorioamnionitis in asymptomatic patients at high risk for spontaneous Address correspondence to: Roberto Romero, M.D., Perinatology Research Branch, NICHD, NIH, DHHS, Wayne State University/ Hutzel Women’s Hospital, 3990 John R, Box 4, Detroit, MI 48201, USA, Telephone (313) 993-2700, Fax: (313) 993-2694, e-mail: [email protected]. NIH Public Access Author Manuscript Ultrasound Obstet Gynecol. Author manuscript; available in PMC 2008 May 21. Published in final edited form as: Ultrasound Obstet Gynecol. 2007 October ; 30(5): 706–714. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript preterm delivery. Furthermore, the combination of ‘sludge’ and a short cervix confers a higher risk for spontaneous preterm delivery at <28 and <32 weeks than that of a short cervix alone.