1002 What category II features prompt the diagnosis of NRFS in the first stage?

Abstract

Non-reassuring fetal status (NRFS), as detected by continuous electronic fetal monitoring (EFM), is a common indication for cesarean delivery (CD) in the first stage. This study aims to identify Category II EFM features that place patients at risk for CD for NRFS. We performed a nested case control study of singleton term pregnancies admitted for labor or induction. Cases were patients with NRFS as the sole indication for CD in the first stage. Controls were all other deliveries without NRFS. We excluded patients with NRFS as a co-indication for CD and second stage NRFS. Trained obstetrical research nurses extracted EFM data from the 60 mins before delivery. The primary outcome was a composite of high risk category II EFM features including minimal variability, recurrent late or variable decelerations, >1 prolonged deceleration, or tachycardia. Secondary outcomes were individual components of the composite, total deceleration area (TDA) and TDA ≥ 90th percentile. We performed a sensitivity analysis comparing first stage CD for NRFS to first stage CD without NRFS. 476 patients had a first stage CD for NRFS. There were 7500 patients who delivered without NRFS. Although presence of composite high-risk Category II EFM features was similar between CD for NRFS and control deliveries [34.7% vs 32.8%, aOR 1.23; 95% CI 0.90-1.69], those undergoing CD for NRFS were more likely to have recurrent late decelerations and ≥ 1 prolonged deceleration and less likely to have minimal variability. TDA was higher in the NRFS group, however TDA>90th percentile was similar between groups. In a sensitivity analysis of first stage CD for NRFS vs first stage CD without NRFS, those with NRFS were more likely to have composite high risk Category II features [aOR 3.59; 95% CI 2.21-5.83]. The majority of first stage CD for NRFS do not have Category II EFM features previously described as ‘high-risk’ for adverse outcomes. Recurrent late and prolonged decelerations are the most common features prompting providers to perform a first stage CD for NRFS.