Quality of intrapartum cardiotocography in twin deliveries

The quality of intrapartum cardiotocography in preterm labour

OBJECTIVES

The aim of this study is to determine the quality of the foetal heart rate (FHR) recording, defined as signal loss, during preterm labour below 28 weeks gestational age (GA) and contribute to the discussion if cardiotocography (CTG) is of value for the extreme preterm foetus.

METHODS

From January 2010 to December 2019 a retrospective study was conducted with data of 95 FHR recordings of singletons born between 24 and 28 weeks GA at the Amsterdam University Medical Centre, location VUmc. FHR tracings had a duration of at least 30 min and were obtained via external ultrasound mode. Data of all recordings were divided in two groups according to gestation (24-26 weeks and 26-28 weeks). Signal loss was analysed. Statistical significance was calculated by non-parametric tests and chi-square tests. The median signal loss and the proportion of cases exceeding the International Federation of Gynaecology and Obstetrics Guidelines (FIGO) threshold of 20% signal loss were calculated.

RESULTS

One-third of the recordings exceeded the 20% FIGO-criterion for adequate signal quality during the first stage of labour. In the second stage, this was nearly 75%. Similarly, the median signal loss was 13% during the first and 30% during the second stage of labour (p<0.01).

CONCLUSIONS

The quality of FHR monitoring in the extreme preterm foetus is inadequate in a large proportion of the foetuses, especially during the second stage. FHR monitoring is therefore controversial and should be used with caution.

Extraction of fetal heart rate from maternal surface ECG with provisions for multiple pregnancies

Twin pregnancies carry an inherently higher risk than singleton pregnancies due to the increased chances of uterine growth restriction. It is thus desirable to monitor the wellbeing of the fetuses during gestation to detect potentially harmful conditions. The detection of fetal heart rate from the maternal abdominal ECG represents one possible approach for noninvasive and continuous fetal monitoring. Here, we propose a new algorithm for the extraction of twin fetal heart rate signals from maternal abdominal ECG recordings. The algorithm detects the fetal QRS complexes and converts the QRS onset series into a binary signal that is then recursively scanned to separate the contributions from the two fetuses. The algorithm was tested on synthetic singleton and twin abdominal recordings. It achieved an average sensitivity and accuracy for QRS complex detection of 97.5% and 93.6%, respectively.

Misidentification of maternal for fetal heart rate patterns after delivery of the first twin

BACKGROUND

The 2nd born in twin delivery is at higher risk of fetal asphyxia. We tested the hypothesis that inadequate, fetal heart rate (FHR) monitoring has contributed to an inadvertent outcome.

STUDY DESIGN

A database was reviewed consisting of 41 twin deliveries with a pH in the umbilical artery of the 2nd twin below 7.05. Cardiotocograms were examined for possible signs of a maternal instead of a fetal origin of the heart rate pattern.

RESULTS

In four of the reviewed cases, a good outcome had been anticipated by the attending physician based on the cardiotocogram, whereas the 2nd twin was born with low Apgar scores and a low pH of the umbilical artery. In retrospect it was concluded that the recorded heart rate pattern was of maternal origin. In all four cases the heart rate tracings had characteristics typical for a maternal origin.

CONCLUSION

Misidentifying the maternal for the fetal heart rate increases the risk that a compromised fetal condition is missed. This occurrence may contribute to the increased incidence of fetal asphyxia in 2nd twins.