Safety of Internal Electronic Fetal Heart Rate Monitoring During Labor

Abstract Objective: To investigate the safety and efficacy of internal electronic fetal heart rate (FHR) monitoring during labor. Methods: This was a retrospective case-control study, which was an analysis of monitoring FHR with a fetal scalp electrode or a Doppler probe (94 pregnant women per group). In the internal monitoring group, when the opening of the uterine orifice was ≥3 cm, the fetal scalp electrode was placed after natural or artificial rupture of the membrane. FHR was simultaneously monitored using a Doppler probe. In the external monitoring group, continuous FHR monitoring was performed using an ultrasound Doppler transducer fixed on the maternal abdomen. The toco transducer was used to record uterine contractions. Pathological examination of the placenta was performed prospectively in 49 and 48 cases in the internal electronic FHR monitoring group and control group, respectively. Maternal-infant outcomes (e.g. fever, puerperal infection, puerperal morbidity, delivery mode, Apgar score, and scalp injury) were recorded. Umbilical artery blood was extracted for blood gas analysis. Differences between the two groups were compared using the paired t-test, χ2 test, Yates corrected χ2 test or Fisher exact test. Results: Non-statistically significant differences between the internal and external monitoring groups were observed in the incidence of neonatal acidosis (1/94 (1.06%) vs. 3/94 (3.19%), respectively; χ2 = 0.255, P = 0.613), cesarean section/operative vaginal delivery (8/94 (8.51%) vs. 15/94 (15.96%), respectively; χ2 = 2.427, P = 0.181), fever during labor (18/94 (19.15%) vs. 15/94 (15.96%), respectively; χ2 = 0.331, P = 0.565), puerperal morbidity (2/94 (2.13%) vs. 3/94 (3.19%), respectively; χ2 = 0.000, P = 1.000), chorioamnionitis (9/49 (18.37%) vs. 7/48 (14.58%), respectively; χ2 = 0.252, P = 0.616), and neonatal asphyxia (0/94 (0.00%) vs. 1/94 (1.06%), respectively; χ2 = 0.000, P = 1.000). There were no puerperal infections, neonatal scalp injuries, or scalp abscesses found in either group. Using the internal monitoring value as reference, the incidence of FHR false deceleration in external FHR monitoring was 20.21% (19/94 women). Conclusion: Internal FHR monitoring during labor does not increase the incidence of adverse perinatal outcomes. External monitoring was associated with FHR false decelerations.