ST segment analysis (STAN) was developed in an attempt to reduce perinatal harm and to minimise the rise in caesarean sections and instrumental births seen with CTG use. STAN technology analyses the shape of the fetal electrocardiogram (ECG or EKG), in particular the ST segment, looking for signs that low oxygen levels are impacting on the function of the heart. It is used in addition to, rather than as a replacement for, CTG monitoring during labour. Meta-analysis of randomised controlled trials has shown no improvement in perinatal mortality or neonatal seizures, and no change in the caesarean section rate (Blix et al., 2015).
New research from Blix and colleagues (2022) has examined the real-world impact of the introduction of STAN systems on maternal and perinatal outcomes. Their research examined outcomes in hospitals in Norway, comparing periods of time prior to and following the introduction of STAN systems. In total, data were collected regarding over one million women with singleton pregnancies who gave birth after 36 weeks of gestation. 76% of hospitals in Norway had adopted STAN technology.
While the rate of stillbirth and neonatal death had fallen during the period 1985 to 2014 when the study was conducted, subsequent analysis showed that this was not associated with the use of STAN technology. Similarly, while caesarean section and instrumental birth rates rose over time, this could also not be ascribed to the introduction of STAN systems. The only statistically significant impact was an increase in the rate of babies born with an Apgar of less than seven at five minutes of age. While statistically significant, the size of the impact was small, with an additional one baby born with a low Apgar for every 3-4000 births. They also looked to see if there was a training effect: that is, that outcomes gradually improved over time as people became familiar with the technology. This was not the case for mortality rates.
While there are limitations to these types of before and after study in proving causation, they do provide useful information about the large-scale impact of new treatments. In the face of this additional evidence that STAN adds no benefits over standard intrapartum CTG monitoring, I wonder whether hospitals will begin to deimplement this technology.
Blix, E., Brurberg, K. G., Reierth, E., Reiner, L. M., & Oian, P. (2015). ST waveform analysis versus cardiotocography alone for intrapartum fetal monitoring: a systematic review and meta-analysis of randomized trials. Acta Obstetricia et Gynecologica Scandinavica, 95(1), 16-27. https://doi.org/10.1111/aogs.12828
Blix, E., Eskild, A., Skau, I., & Grytten, J. (2022). The impact of the introduction of intrapartum fetal ECG ST segment analysis. A population study. Acta Obstetrica et Gynecologica Scandanavica, in press, 1-10. https://doi.org/10.1111/aogs.14347