Evolving Frameworks for the Foundation and Practice of Electronic Fetal Monitoring

Since the 1970s,electronic fetal monitoring(EFM)also known as cardiotocography(CTG)has been used extensively in labor around the world,despite its known failure to help prevent many babies from developing neonatal encephalopathy and cerebral palsy.Part of EFM’s poor performance with respect to these outcomes arises from a fundamental misunderstanding of the differences between screening and diagnostic tests,subjective classifications of fetal heart rate(FHR)patterns that lead to large inter-observer variability in its interpretation,failure to appreciate early stages of fetal compromise,and poor statistical modeling for its use as a screening test.We have developed a new approach to the practice and interpretation of EFM called the fetal reserve index(FRI)which does the following:(1)breaking FHR components down into 4 components,(heart rate,variability,accelerations,and decelerations);(2)contextualizing the metrics by adding increased uterine activity;(3)adding specific maternal,fetal,and obstetric risk factors.The result is an eight-point scoring metric that,when directly compared with current American College of Obstetricians and Gynecologists EFM categories,even in version 1.0 with equal weighting of variables,shows that the FRI has performed much better for identifying cases at risk before damage had occurred,reducing the need for emergency deliveries,and lowering overall Cesarean delivery rates.With increased data,we expect further refinements in the specifics of scoring that will allow even earlier detection of compromise in labor.

Applicability of initial optimal maternal and fetal electrocardiogram combination vectors to subsequent recordings

A series of experiments are conducted to confirm whether the vectors calculated for an early section of a continuous non-invasive fetal electrocardiogram （fECG） recording can be directly applied to subsequent sections in order to reduce the computation required for real-time monitoring. Our results suggest that it is generally feasible to apply the initial optimal maternal and fetal ECG combination vectors to extract the fECG and maternal ECG in subsequent recorded sections.

Safety of Internal Electronic Fetal Heart Rate Monitoring During Labor

Objective:To investigate the safety and efficacy of internal electronic fetal heart rate(FHR)monitoring during labor.Methods:This was a retrospective case-control study,which was an analysis of monitoring FHR with a fetal scalp electrode or a Doppler probe(94 pregnant women per group).In the internal monitoring group,when the opening of the uterine orifice was≥3 cm,the fetal scalp electrode was placed after natural or artificial rupture of the membrane.FHR was simultaneously monitored using a Doppler probe.In the external monitoring group,continuous FHR monitoring was performed using an ultrasound Doppler transducer fixed on the maternal abdomen.The toco transducer was used to record uterine contractions.Pathological examination of the placenta was performed prospectively in 49 and 48 cases in the internal electronic FHR monitoring group and control group,respectively.Maternal-infant outcomes(e.g.fever,puerperal infection,puerperal morbidity,delivery mode,Apgar score,and scalp injury)were recorded.Umbilical artery blood was extracted for blood gas analysis.Differences between the two groups were compared using the pairedt-test,χ^(2) test,Yates correctedχ^(2) test or Fisher exact test.Results:Non-statistically significant differences between the internal and external monitoring groups were observed in the incidence of neonatal acidosis(1/94(1.06%)vs.3/94(3.19%),respectively;χ^(2)=0.255,P=0.613),cesarean section/operative vaginal delivery(8/94(8.51%)vs.15/94(15.96%),respectively;χ^(2)=2.427,P=0.181),fever during labor(18/94(19.15%)vs.15/94(15.96%),respectively;χ^(2)=0.331,P=0.565),puerperal morbidity(2/94(2.13%)vs.3/94(3.19%),respectively;χ^(2)=0.000,P=1.000),chorioamnionitis(9/49(18.37%)vs.7/48(14.58%),respectively;χ^(2)=0.252,P=0.616),and neonatal asphyxia(0/94(0.00%)vs.1/94(1.06%),respectively;χ^(2)=0.000,P=1.000).There were no puerperal infections,neonatal scalp injuries,or scalp abscesses found in either group.Using the internal monitoring value as reference,the incidence of FHR false deceleration in external FHR monitoring was 20.21%(19/94 women).Conclusion:Internal FHR monitoring during labor does not increase the incidence of adverse perinatal outcomes.External monitoring was associated with FHR false decelerations.

The Efficacy of In-Phase and Quadrature Demodulation in Electronic Fetal Heart Rate Monitoring During Labor

Objective:To investigate the efficacy of in-phase and quadrature(IQ)demodulation in electronic fetal heart rate monitoring(EFM)to reduce false reports of fetal heart rate(FHR)doubling or halving.Methods:This is a prospective cohort study.A total of 263 full-term pregnant women who delivered at Peking University Shenzhen Hospital between August 2019 and July 2020 were prospectively enrolled in the study.FHR monitoring began when the cervix was dilated to 2-3 cm and continued until delivery.Raw fetal Doppler audio signals and internal and external cardiotocography curves from internal electrode monitoring,EFM with conventional demodulation(external),and EFM with IQ demodulation(external)were acquired to compare FHR doubling and halving time.In cohort 1,FHR was compared between IQ demodulation and conventional demodulation.In cohort 2,FHR was compared between IQ demodulation,conventional demodulation,and internal FHR monitoring.Count data were statistically analyzed using the Chi-squared test,and measurement data were statistically analyzed usingt-test for correlation coefficients,and Bland-Altman analysis for concordance ranges.Results:To compare IQ demodulation and conventional demodulation,225 pregnant women were monitored for a total of 835,870 seconds.The beat-to-beat interval of FHRs in raw fetal Doppler audio signals was used as the reference.The results showed a doubling time of 3401 seconds(0.407%,3401/835,870)and a halving time of 2918 seconds(0.349%,2918/835,870)with conventional demodulation,compared to 241 seconds(0.029%,241/835,870)and 589 seconds(0.070%,589/835,870),respectively,with IQ demodulation.IQ demodulation reduced FHR doubling by approximately 93%(3160/3401)and FHR halving by approximately 80%(2329/2918)compared to conventional demodulation(P<0.01).Conclusion:EFM with IQ demodulation significantly reduces false FHR doubling and halving,with an efficacy similar to that of internal FHR monitoring.

Computerized Analysis of Antepartum Cardiotocography: A Review

Cardiotocography measures the human fetal heart rate and uterine activity using ultrasound.While it has been a mainstay in antepartum care since the 1960s,cardiotocograms consist of complex signals that have proven difficult for clinicians to interpret accurately and as such clinical inference is often difficult and unreliable.Previous attempts at codifying approaches to analyzing the features within these signals have failed to demonstrate reliability or gain sufficient traction.Since the early 1990s,the Dawes-Redman system of automated computer analysis of cardiotocography signals has enabled robust analysis of cardiotocographic signal features,employing empirically-derived criteria for assessing fetal wellbeing in the antepartum.Over the past 30 years,the Dawes-Redman system has been iteratively updated,now incorporating analyses from over 100,000 pregnancies.In this review,we examine the history of cardiotocography,signal processing methodologies and feature identification,the development of the Dawes-Redman system,and its clinical applications.

Interobserver Agreement and Reliability of Intrapartum Nonreassuring Cardiotocography and Prediction of Neonatal Acidemia

Objective:To evaluate the agreement and reliability of intrapartum nonreasurring cardiotocography(CTG)interpretation and prediction of neonatal acidemia by obstetricians working in different centers.Methods:A retrospective cohort study involving two tertiary hospitals(The First Affiliated Hospital of Sun Yat-sen University and Perking University Third Hospital)was conducted between 30th September 2018 and 1st April 2019.Six obstetricians from two hospitals with three levels of experience(junior,medium,and senior)reviewed 100 nonreassuring fetal heart rate(FHR)tracings from 1 hour before the onset of abnormalities until delivery.Each reviewer determined the FHR pattern,the baseline,variability,and presence of acceleration,deceleration,sinusoidal pattern,and predicted whether neonatal acidemia and abnormal umbilical arterial pH<7.1 would occur.Inter-observer agreement was assessed using the proportions of agreement(Pa)and the proportion of specific agreement(Pa for each category).Reliability was evaluated with the kappa statistic(k-Light’s kappa for n raters)and Gwet’s AC1 statistic.Results:Good inter-observer agreement was found in evaluation of most variables(Pa>0.5),with the exception of early deceleration(Pa=0.39,95%confidence interval(CI):0.36,0.43).Reliability was also good among most variables(AC1>0.40),except for acceleration,early deceleration,and prediction of neonatal acidemia(AC1=0.17,0.10,and 0.25,respectively).There were no statistically significant differences among the three groups,except in the identification of accelerations(Pa=0.89,95%CI:0.83,0.95;Pa=0.50,95%CI:0.41,0.60,and Pa=0.35,95%CI:0.25,0.43 in junior,medium and senior groups,respectively)and the prediction of neonatal acidemia(Pa=0.52,0.52,and 0.62 in junior,medium and senior groups,respectively),where agreement was highest and lowest in the junior-level group,respectively.The accuracy and sensitivity of the prediction for umbilical artery pH<7.1 were similar among the three groups,but the specificity was higher in the senior groups(93.68%vs.92.53%vs.98.85%in junior,medium and senior groups,P=0.015).Conclusion:Although we found a good inter-observer agreement in the evaluation of the most basic CTG features and FHR category statistically,it was insufficient to meet the clinical requirements for"no objection"interpretation for FHR tracings.Further specialized training is needed for standardized interpretation of intrapartum FHR tracings.