Association of amniotic fluid sludge with preterm labor and histologic chorioamnionitis in pregnant Japanese women with intact membranes: A retrospective study

Aim The presence of amniotic fluid sludge has been identified as a risk factor for preterm birth. We sought to validate the clinical characteristics of amniotic fluid sludge in Japanese pregnant women with preterm labor and intact membranes. Methods This was a retrospective study of 54 patients. The presence of amniotic fluid sludge was confirmed using transvaginal ultrasonography data during pregnancy. The following data were collected: gestational age, the presence of histologic chorioamnionitis, time from the diagnosis of threatened premature labor to delivery, oncofetal fibronectin (onfFN) levels, C-reactive protein peak value levels, cervical length at the time of onset of threatened premature labor and types of neonatal complications. Results Significant differences (P = 0.03) were observed in the age at delivery in relation to the presence of amniotic sludge: delivery occurred at 28.3 +/- 4.5 weeks and 31.7 +/- 4.3 weeks in sludge positive patients and sludge-negative patients, respectively. Presence of sludge in patients diagnosed with histological chorioamnionitis at <37 weeks of gestation differed significantly (P = 0.01): sludge-positive, 81.8%; sludge-negative, 20.9%. Among the sludge-positive patients, 100% were positive for serum onfFN (>= 50 ng/mL), whereas only 54% of sludge-negative patients were positive for serum onfFN (P = 0.03). Presence of amniotic fluid sludge did not significantly affect neonatal complications. Conclusion Our results confirmed previous findings that amniotic fluid sludge is a self-determining risk factor for preterm birth and chorioamnionitis in pregnant Japanese women.