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 benefit in terms of fetal morbidity and mortality are controversial. While early trials could not demonstrate a benefit from intrapartum monitoring [1, 2], a recent systematic review and meta analysis published by the Cochrane Collaboration clarifies 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 significant difference in the overall perinatal death rate compared to intermittent auscultation [relative risk (RR) 0.85, 95% confidence 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 significant 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 significantly 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 wave recorded by a fetal scalp electrode to determine the fetal stress status. In a study of 1,200 parturients from the UK, Westgate et al. [6] successfully demonstrated that fetal ST waveform analysis in addition to a non-reassuring electrocardiotocogram significantly reduces the proportion of deliveries for fetal distress (cases 27/615 vs. controls 58/606; P < 0.001) [4]. This finding was fully confirmed in a large Swedish study of 4,966 parturients [5]. Using the same study design, Amer-Wahlin et al. [7] showed that the intervention group (cardiotocography + fetal ST wave monitoring) had significantly lower rates of umbilical artery metabolic acidosis than the control group (cardiotocography only) [15 of 2,159 (0.7%) vs. 31 of 2,079 (2%), RR 0.47 (95% CI 0.25–0.86), P = 0.02] and a lower rate of operative delivery for fetal distress [193 of 2,519 (8%) vs. 227 of 2,447 (9%), RR 0.83 (0.69–0.99), P = 0.047]. Despite these data leaving no doubt as to the validity of this method, it has to be acknowledged that the difference between both groups (8 vs. 9%) i.e., the number of operative deliveries avoided, was small and of doubtful clinical relevance. Consequently, fetal ST waveform analysis has not yet gained widespread acceptance. This may be due to the small benefit involved, high costs associated with the necessary equipment, unwillingness of adding more technology to the labor ward or a combination of these factors.

In summary, it seems clear that despite numerous and well-designed clinical trials involving significant technology, intrapartum fetal monitoring by cardiotocography has not been improved during the last two decades. Obviously, fetal monitoring has arrived at a level, which is difficult to improve within the given clinical and technical settings. If we accept trading in low rates of operative delivery for an improved fetal morbidity, research resources may be better placed in other areas of concern, namely preeclampsia, premature rupture of membranes, placental insufficiency and premature labor. Compared to the valuable endeavour of reducing high rates of cesarean delivery i.e. due to continuous intrapartum fetal monitoring, it should be accepted that the stakes of human suffering as well as health-care costs are much higher in other areas, premature delivery and its sequelae.