Introduction
Cardiotocography (CTG), also referred to as electronic foetal monitoring
(EFM), is the most widely used non-invasive foetal heart rate (FHR)
monitoring before and during labour 1, 2. Foetal
hypoxia and acidosis could be detected primarily through the recognition
of specific patterns on the CTG signal (e.g., decelerations)3-5. These CTG patterns, however, are difficult for
human visual interpretation to reliably and consistently identify1, 6, 7. It is well-established that subjective
assessment of the CTG patterns suffers from poor inter-observer and
intra-observer reproducibility 1, 8-13 and is
associated with increased operative vaginal delivery and Caesarean
section rates without improving perinatal outcomes 14,
15. Computerised cardiotocography (cCTG) has been considered to be
superior to conventional CTG as this approach provides more reliable and
consistent interpretation of the CTG tracing 1, 2, 16,
17. Based on specific criteria of Dawes-Redman system, cCTG enables
quantitative and objective evaluation of the foetal state1, 2. Results from earlier studies comparing human
visual analysis and computerised analysis of FHR tracing supported the
idea that computerised analysis could overcome the subjectivity of
visual interpretation of FHR tracing 18, 19.
Short-term variation (STV) is the measurement of beat-to-beat variation
in the FHR over a very short time scale provided by cCTG20. A study demonstrated that the risk of metabolic
acidaemia increased as the antepartum cCTG STV decreased; at the optimal
cut-off level at 3.0 milliseconds or less, the positive and negative
predictive values were 64.6% and 86.6%, respectively21. The Dawes-Redman approach has the advantages of
enabling objective evaluation of cCTG STV and analyzing the CTG trace
with information on foetal movements, presence of sinusoidal patterns,
and quality of the electronic tracing 1. It has been
observed that there is increasing use of cCTG for the evaluation of
foetal wellbeing especially for high-risk cases, including those with
foetal growth restriction (FGR) and preeclampsia 2, 16,
22. As such, the International Society of Ultrasound in Obstetrics and
Gynecology (ISUOG) has integrated the use of cCTG STV in a recent
guideline for the monitoring and management of pregnancies with FGR22.
Doppler velocimetry by examining the uterine artery pulsatility index
(UtA-PI), umbilical artery pulsatility index (UA-PI), middle cerebral
artery pulsatility index (MCA-PI) and cerebroplacental ratio (CPR)
(which is the ratio between MCA-PI and UA-PI), can evaluate
uteroplacental function and allow for the detection of uteroplacental
insufficiency 23-26. These Doppler indices are
important in the diagnosis, monitoring, and management of high-risk
pregnancies especially for those with FGR 22, 27-29.
In addition, evidence shows that monitoring and delivery timing
according to a specific protocol including Doppler indices and cCTG
provide better-than-expected outcomes for fetuses diagnosed with FGR30.
Despite solid evidence supporting the use of cCTG and Doppler
velocimetry in the management of pregnancies complicated with FGR, there
is a scarcity of data on the clinical utility of cCTG and Doppler
velocimetry in pregnancies in other clinical scenarios, such as during
latent phase of labour or before induction of labour. This study aimed
to investigate the relationship and the potential value of prelabour
maternal-foetal Dopplers and cCTG STV in predicting labour outcomes
including umbilical cord arterial pH, emergency delivery due to
pathological CTG during labour and neonatal intensive care unit
(NICU)/special care baby unit (SCBU) admission.