Adding maternal heart rate monitoring to electronic fetal monitoring was associated with better neonatal outcomes.

Intrapartum electronic fetal monitoring is used in high-risk pregnancies to monitor for signs of fetal hypoxia. It also is used commonly in pregnancies with low risk for fetal hypoxia, despite considerable uncertainty regarding the balance of harms and benefits.

In a large retrospective cohort of about 210,000 singleton term vaginal deliveries from 2005 to 2023, Finnish researchers compared neonatal outcomes associated with three intrapartum fetal monitoring methods: invasive monitoring via fetal scalp electrode (FSE; 33% of deliveries), noninvasive (i.e. external) abdominal ultrasound transducer alone (38% of deliveries) and noninvasive abdominal ultrasound transducer with concomitant maternal heart rate monitoring (MHR; 29% of deliveries). MHR was either via pulse oximetry or as a component of the abdominal ultrasound transducer. The neonatal outcomes tracked in this study were umbilical artery pH, Apgar scores, need for intubation and resuscitation, neonatal intensive care unit admission for asphyxia, neonatal encephalopathy and early neonatal death.

Key results were as follows:

• compared with ultrasound plus MHR, use of ultrasound alone was associated with significantly higher odds of neonatal encephalopathy (odds ratio [OR], 1.48), severe acidaemia (pH, below 7.0; OR, 1.97), and neonatal intubation (OR, 1.22)
• invasive monitoring with FSE was associated with significantly lower odds of severe acidaemia than ultrasound plus MHR, but rates of neonatal encephalopathy or intubation did not differ
• 16 neonatal deaths occurred in the ultrasound-alone group and five and six, respectively, in the ultrasound plus MHR and FSE groups, although the differences were not statistically significant.

Comment: A concern with noninvasive fetal monitoring is that a maternal tachycardia might be misidentified as a reassuring fetal heart rate. Despite the inherent limitations of the observational study design, these results suggest that adding maternal heart rate monitoring as part of noninvasive intrapartum fetal monitoring in centres where it is not standard practice is a feasible, relatively low-cost intervention to improve perinatal morbidity and mortality.

Marie Claire O’Dwyer, MB BCh BAO, MPH, Clinical Assistant Professor in Family Medicine, University of Michigan Medical School, Ann Arbor, USA.

Tarvonen M, et al. Intrapartum cardiotocography with simultaneous maternal heart rate registration improves neonatal outcome. Am J Obstet Gynecol 2024; 230: 379.e1-379.e12.

This summary is taken from the following Journal Watch title: Women’s Health.