Chorioamnionitis following preterm premature rupture of membranes and fetal heart rate variability

INTRODUCTION The objective of this study was to identify prenatal markers of histological chorioamnionitis (HC) during pPROM using fetal computerized cardiotocography (cCTG). MATERIALS AND METHODS Retrospective review of medical records from pregnant women referred for pPROM between 26 and 34 weeks, in whom placental histology was available, in a tertiary level obstetric service over a 5-year period. Fetal heart rate variability was assessed using cCTG. Patients were included if they were monitored at least six times in the 72 hours preceding delivery. Clinical and biological cCTG parameters during the pPROM latency period were compared between cases with or without HC. RESULTS In total, 222 pPROM cases were observed, but cCTG data was available in only 23 of these cases (10 with and 13 without HC) after exclusion of co-morbidities which may potentially perturb fetal heart rate variability measures. Groups were comparable for maternal age, parity, gestational age at pPROM, pPROM duration and neonatal characteristics (p>0.1). Baseline fetal heart rate was higher in the HC group [median 147.3 bpm IQR (144.2-149.2) vs. 141.3 bpm (137.1-145.4) in no HC group; p = 0.02]. The number of low variation episodes [6.4, (3.5-15.3) vs. 2.3 (1-5.2); p = 0.04] was also higher in the HC group, whereas short term variations were lower in the HC group [7.1 ms (6-7.4) vs. 8.1 ms (7.4-9); p = 0.01] within 72 hours before delivery. Differences were especially discriminant within 24 hours before delivery, with less short-term variation [5 ms (3.7-5.9) vs. 7.8 ms (5.4-8.7); p = 0.007] and high variation episodes [3.9 (4.9-3.2) vs. 0.8 (1.5-0.2); p < 0.001] in the HC group. CONCLUSION These results show differences in fetal heart rate variability, suggesting that cCTG could be used clinically to diagnoses chorioamnionitis during the pPROM latency period.