New fetal heart monitor works, but clinicians don't know how to use it

December 1, 2007

The STAN S 21 fetal heart monitor--developed in Sweden and widely used throughout Scandinavia--failed to alter the incidence of emergency operative deliveries or of neonatal encephalopathy (NNE).

The STAN S 21 fetal heart monitor-developed in Sweden and widely used throughout Scandinavia - failed to alter the incidence of emergency operative deliveries or of neonatal encephalopathy (NNE), according to a review of its use in 1,502 laboring women in a London teaching hospital.

The reason, according to the authors of the study, isn't that the technology, which combines cardiotography (CTG) (fetal heart rate monitoring and internal contraction monitoring) with ST waveform analysis, doesn't work, but rather that users are often less than proficient at CTG interpretation, delay in taking action when it is indicated, and do not adhere to usage guidelines.

In fact, the technology worked fairly well. In the study, action was indicated in 23.8% of the women and not indicated in 73.8%. Traces were uninterpretable in 2.4%. Of the 836 (55.7%) cases with available cord blood gas determinations, 16 of the 23 cases with metabolic acidosis, 16 of the 23 cases with low Apgar scores, and 4 of the 5 cases with metabolic acidosis combined with a low Apgar score were preceded by a significant STAN event.

The monitor comes with what are supposed to be clear guidelines as to when intervention (either delivery or alleviation of a cause of fetal distress, such as uterine overstimulation or maternal hypotension) is required. But as a result of user problems throughout Europe, a meeting was held earlier this year in the Netherlands to revise STAN guidelines and measures in an effort to reduce user errors and ambiguity and the risk of adverse outcomes. Additional study will be required to determine whether their efforts were successful.

Doria V, Papageorghiou AT, Gustafsson A, et al. Review of the first 1502 cases of ECG-ST waveform analysis during labour in a teaching hospital. BJOG. 2007;114:1202-1207.

Amer-Wahlin I, Arulkumaran S, Hagberg H, et al. Fetal electrocardiogram: ST waveform analysis in intrapartum surveillance. BJOG. 2007;114:1191-1193.