Modern intrapartum fetal monitoring: room for improvement?

Abstract

Electronic fetal heart monitoring is the standard of care for intrapartum surveillance of the fetus. Despite its widespread use and general acceptance, data regarding the clinical beneWt in terms of fetal morbidity and mortality are controversial. While early trials could not demonstrate a beneWt from intrapartum monitoring [1, 2], a recent systematic review and meta analysis published by the Cochrane Collaboration clariWes that electronic fetal heart rate monitoring by cardiotocography does not reduce fetal mortality, but reduces neonatal seizures by 50%. Based on 22 randomized trials, continuous cardiotocography showed no signiWcant diVerence in the overall perinatal death rate compared to intermittent auscultation [relative risk (RR) 0.85, 95% conWdence interval (CI) 0.59–1.23, n = 33,513, 11 trials], but was associated with a halving of neonatal seizures (RR 0.50, 95% CI 0.31–0.80, n = 32,386, 9 trials). Cardiotocography had no signiWcant impact on the rates of cerebral palsy (RR 1.74, 95% CI 0.97–3.11, n = 13,252, 2 trials) [3]. Therefore, it is clear that electronic fetal heart rate monitoring is a valuable instrument for improving fetal morbidity. It comes, however, at a high price for the mother, because it signiWcantly increases the risk of cesarean section (RR 1.66, 95% CI 1.30–2.13, n = 18,761, 10 trials) as well as vaginal operative delivery (RR 1.16, 95% CI 1.01–1.32, n = 18,151, 9 trials) [3]. After the widespread acceptance of continuous electronic fetal heart rate monitoring, numerous interventions have been tested in an attempt to reduce the increased rate of operative deliveries while at the same time maintaining or improving fetal safety, among them fetal scalp blood sampling, fetal ST waveform analysis and fetal pulse oxymetry. Only fetal scalp blood sampling, however, has been implicated into clinical practice so far. Fetal scalp blood sampling and the subsequent assessment of fetal pH or lactate values is a promising method using equipment readily available in the labor ward. Despite its common use and interesting experimental data and correlations with perinatal fetal outcome, fetal scalp blood sampling has not been tested in randomized trials. Thus, there are no data allowing for an evidence-based recommendation of this method as an adjunct to non-reassuring fetal heart rate patterns on cardiotocography. Based on what we know today, fetal pulse oxymetry is not helpful in improving maternal or fetal outcomes. Bloom et al. [4] clearly demonstrated in a recent large randomized trial of 5,341 nulliparous women that fetal pulse oxymetry is not associated with a reduced rate of cesarean delivery or with an improvement in perinatal morbidity and mortality. This is in accordance with a previous Cochrane Collaboration review [5], making further trials of this diagnostic method seem unpromising. On the other hand, fetal ST waveform analysis has been shown to reduce the rate of cesarean section in two properly designed randomised trials [6, 7]. This technique uses electrocardiogram analysis of the ST C. Tempfer · L. HeXer · P. Husslein Department of Obstetrics and Gynecology, Medical University of Vienna, Vienna, Austria