Category II Fetal Monitoring in Fetuses With Congenital Heart Defects: Are They Any Different? [06O

Abstract

INTRODUCTION: The majority of literature investigating continuous electronic fetal monitoring (EFM) excludes anomalous fetuses. The objective of this study was to determine if Category II EFM characteristics differed between fetuses with and without congenital heart defects (CHD). METHODS: This was a retrospective IRB-approved cohort study of singleton, term pregnancies admitted for induction or labor with an antenatal diagnosis of fetal CHD between 2017–2019. We excluded fetuses with genetic abnormalities. Cases were matched by race and obesity in a 1:2 ratio to a historic control of term pregnancies with structurally normal fetuses. EFM characteristics in the 1 hour before delivery were extracted. The primary outcome was incidence of Category II EFM features; secondary outcome was total deceleration area (TDA). RESULTS: 47 cases of fetal CHD were matched to 94 controls. There was no difference in advanced maternal age, other baseline demographics, or mode of delivery between groups. Fetuses with CHD were less likely to have prolonged decelerations (6.4 vs 25.5%, P<.01) or any periods of tachycardia (4.3 vs 17.0, p 0.03) compared to normal fetuses. Other Category II features were similar between groups including incidence of recurrent late and variable decelerations and minimal variability. There was no difference in TDA between groups. CONCLUSION: Prolonged decelerations and tachycardia were less common in CHD fetuses. The incidence of other Category II features were similar to nonanomalous fetuses. These results suggest that structural heart defects do not increase the risk of concerning EFM patterns. Future studies should evaluate the risk of acidemia with Category II EFM and CHD.