Intrapartum cardiotocography with simultaneous maternal heart rate registration improves neonatal outcome.

BACKGROUND: Intrapartum cardiotocographic monitoring of fetal heart rate by abdominal external ultrasound transducer without simultaneous maternal heart rate recording has been associated with increased risk of early neonatal death and other asphyxia-related neonatal outcomes. It is unclear, however, whether this increase in risk is independently associated with fetal surveillance method or is attributable to other factors.

OBJECTIVES: In a large retrospective cohort of deliveries, the aim of the present study was to compare different fetal surveillance methods and their association with adverse short-term and long-term fetal and neonatal outcomes.

STUDY DESIGN: Fetal heart rate and maternal heart rate patterns were recorded by cardiotocography during the labor in spontaneous term singleton cephalic vaginal deliveries in the Hospital District of Helsinki and Uusimaa, Finland between October 1st 2005, and September 30th 2023. According to the method of cardiotocography monitoring at birth, the cohort was divided into three groups: women with ultrasound transducer, women with both ultrasound transducer and maternal heart rate transducer, and women with internal fetal scalp electrode. Umbilical artery pH and base excess values, low one- and five-minute Apgar scores, need for intubation and resuscitation, neonatal intensive care unit admission for asphyxia, neonatal encephalopathy, and early neonatal death were used as outcome variables.

RESULTS: Of the 213,798 deliveries that met the inclusion criteria, the monitoring type was external ultrasound transducer in 81,559 (38.1%), both external ultrasound transducer and maternal heart rate recording in 62,268 (29.1%), and fetal scalp electrode in 69,971 (32.7%) cases, respectively. Compared with concurrent external fetal and maternal heart rate recording both neonatal encephalopathy (odds ratio 1.48, 95% confidence interval 1.08-2.02) and severe acidemia (UA pH <7.00 and/or UA BE ≤-12.0 mmol/L) (odds ratio 2.03, 95% confidence interval 1.65-2.50) were significantly higher in fetuses of women with ultrasound transducer alone. Monitoring with ultrasound transducer alone was also associated with increased risk of neonatal intubation for resuscitation (odds ratio 1.22, 95% confidence interval 1.03-1.44). A greater risk of severe neonatal acidemia was observed both in the ultrasound transducer (odds ratio 2.78, 95% confidence interval 2.23-3.48) and concurrent ultrasound transducer and maternal heart rate recording (odds ratio 1.37, 95% confidence interval 1.05-1.78) groups compared with those monitored with fetal scalp electrode. No difference in risk of neonatal encephalopathy was found between newborns monitored with concurrent ultrasound transducer and maternal heart rate recording and those monitored with fetal scalp electrode.

CONCLUSIONS: The use of external ultrasound transducer monitoring of fetal heart rate without simultaneous maternal heart rate recording is associated with higher rate of neonatal encephalopathy and severe neonatal acidemia. We suggest that external fetal heart rate monitoring with concurrent maternal heart rate recording, or internal fetal scalp electrode, should be used routinely as a fetal surveillance tool in term labors.