"Does short-term variation in fetal heart rate predict fetal acidaemia?" A systematic review and meta-analysis

Is short-term-variation of fetal-heart-rate a better predictor of fetal acidaemia in labour? A feasibility study

Background

Continuous intrapartum fetal monitoring is challenging and its clinical benefits are debated. The project evaluated whether short-term-variation (STV) and other computerised fetal heart rate (FHR) parameters (baseline FHR, long-term-variation, accelerations and decelerations) predicted acidaemia at birth. The aims of the study were to assess the changes in FHR pattern during labour and determine the feasibility of undertaking a definitive trial by reporting the practicalities of using the monitoring device, participant recruitment, data collection and staff training.

Methods

200 high-risk women carrying a term singleton, non-anomalous fetus, requiring continuous FHR monitoring in labour were consented to participate from the Jessop Wing maternity unit, Sheffield, UK. The trans-abdominal fetal ECG monitor was placed as per clinical protocol. During the monitoring session, clinicians were blinded to the computerised FHR parameters. We analysed the last hour of the FHR and its ability to predict umbilical arterial blood pH <7.20 using receiver operator characteristics (ROC) curves.

Results

Of 200 women, 137 cases were excluded as either the monitor did not work from the onset of labour (n = 30), clinical staff did not return or used the monitor on another patient (n = 37), umbilical cord blood not obtained (n = 25), FHR data not recorded within an hour of birth (n = 34) and other reasons (n = 11). In 63 cases included in the final analysis, the computer-derived FHR parameters did not show significant correlation with umbilical artery cord pH <7.20. Labour was associated with a significant increase in short and long term variation of FHR and number of deceleration (P<0.001). However, baseline FHR decreased significantly before delivery (P<0.001).

Conclusions

The project encountered a number of challenges, with learning points crucial to informing the design of a large study to evaluate the potential place of intrapartum computerised FHR parameters, using abdominal fetal ECG monitor before its clinical utility and more widespread adoption can be ascertained.

Computerized fetal heart rate analysis in early preterm fetal growth restriction

OBJECTIVE

To assess the value of computerized cardiotocography (cCTG) with calculation of fetal heart rate (FHR) short-term variability (STV) in early preterm fetal growth restriction (FGR) for prevention of fetal death and neonatal asphyxia, neonatal morbidity, and 2-year neurodevelopmental impairment.

METHODS

This was a retrospective cohort study of all women who were admitted to the Amsterdam University Medical Center-AMC between 2003 and 2015 due to FGR and/or pre-eclampsia, and who were delivered by prelabor Cesarean section, or had a fetal death, before 32 weeks' gestation. STV of all available cCTG registrations during the 5 days preceding fetal death or delivery was calculated retrospectively, and FHR decelerations were classified visually as absent, 1-2/h or recurrent (> 2/h). Adverse outcome endpoints were defined as fetal death, neonatal asphyxia at birth (including fetal death), neonatal death, major neonatal morbidity and 2-year neurodevelopmental outcome. A simulation analysis was performed to assess the incidence of adverse outcome using two thresholds for cCTG: (1) highly abnormal (STV < 2.6 ms before 29 weeks and < 3.0 ms thereafter, and/or recurrent FHR decelerations); and (2) moderately abnormal (STV < 3.5 ms before 29 weeks and < 4.0 ms thereafter, and/or recurrent FHR decelerations). Three management strategies were assessed using a strict schedule for the frequency of cCTG recordings: (1) cCTG without use of fetal arterial Doppler; (2) cCTG with additional fetal arterial Doppler after 29 weeks; and (3) cCTG with additional fetal arterial Doppler after 27 weeks.

RESULTS

Included were 367 pregnancies (3295 cCTG recordings), of which 20 resulted in fetal death and 347 were delivered by Cesarean section before the onset of labor. Cesarean delivery was indicated by fetal condition in 94% of cases and by maternal condition in 6%. Median gestational age at delivery was 30 (interquartile range (IQR), 28-31) weeks and median birth weight was 900 (IQR, 740-1090) g. Six cases of fetal death were not anticipated by standard practice using visual assessment of CTG. A last highly abnormal cCTG was associated with fetal death and with neonatal asphyxia (including fetal death; n = 99), but not with major neonatal morbidity and 2-year neurodevelopmental outcome. Moderately abnormal cCTG had no significant association with any endpoint. Simulation analysis showed that a strategy that combined cCTG results with umbilicocerebral ratio or umbilical absent or reversed end-diastolic flow could detect all fetal deaths.

CONCLUSIONS

Computerized CTG in combination with fetal arterial Doppler, with a strict protocol for the frequency of recordings, is likely to be more effective than visual CTG assessment for preventing fetal death in early preterm FGR. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Autonomic response to fetal acidosis using an experimental sheep model

BACKGROUND

The autonomic nervous system has a major role in fetal adaptation to hypoxia. Its activity might be assessed using heart rate variability and heart rate deceleration analyses.

OBJECTIVE

To evaluate the ability of different heart rate variability and morphological deceleration analyses to predict fetal acidosis during labor in an experimental fetal sheep model.

STUDY DESIGN

Repeated 1-minute total umbilical cord occlusions were performed at mild (1minute every 5 min), moderate (1 min every 3 min), and severe (1 min every 2 min) umbilical cord occlusion periodicities until arterial pH reached 7.10. Hemodynamic,blood gas analysis, morphological analysis of decelerations (magnitude, slope, and area ofdecelerations), and heart rate variability parameters were recorded throughout the experiment.Heart rate variability analysis included temporal analysis (root mean square of successivedifferences between adjacent RR intervals, standard deviation of normal to normal RR intervals, short term variability), spectral analysis (low frequencies, high frequencies,normalized high frequencies), and a new index developed by our team, the Fetal Stress Index.We defined and compared three pH groups: >7.20, 7.10-7.20, and <7.10.

RESULTS

Eleven experiments were performed. Repetitive umbilical cord occlusions resulted in progressive fetal acidosis. Fetal Stress Index was correlated with pH and lactate (p < 0.05) and increased with acidosis. There were no significant correlations between pH, lactate, and other indices (spectral analysis, temporal analysis, or morphological analysis of decelerations).

CONCLUSION

This protocol allowed us to identify the progressive onset of fetal acidosis in an experimental model close to labor. Fetal Stress Index is a heart rate variability method that varies with acidosis and indicates an increase in parasympathetic nervous system activity in response to fetal acidosis.

Comparative analysis of 2-year outcomes in GRIT and TRUFFLE trials

OBJECTIVE

To explore the effect on perinatal outcome of different fetal monitoring strategies for early-onset fetal growth restriction (FGR).

METHODS

This was a cohort analysis of individual participant data from two European multicenter trials of fetal monitoring methods for FGR: the Growth Restriction Intervention Study (GRIT) and the Trial of Umbilical and Fetal Flow in Europe (TRUFFLE). All women from GRIT (n = 238) and TRUFFLE (n = 503) who were randomized between 26 and 32 weeks' gestation were included. The women were grouped according to intervention and monitoring method: immediate delivery (GRIT) or delayed delivery with monitoring by conventional cardiotocography (CTG) (GRIT), computerized CTG (cCTG) only (GRIT and TRUFFLE) or cCTG and ductus venosus (DV) Doppler (TRUFFLE). The primary outcome was survival without neurodevelopmental impairment at 2 years of age.

RESULTS

Gestational age at delivery and birth weight were similar in both studies. Fetal death rate was similar between the GRIT and TRUFFLE groups, but neonatal and late death were more frequent in GRIT (18% vs 6%; P < 0.01). The rate of survival without impairment at 2 years was lowest in pregnancies that underwent immediate delivery (70% (95% CI, 61-78%)) or delayed delivery with monitoring by CTG (69% (95% CI, 57-82%)), increased in those monitored using cCTG only in both GRIT (80% (95% CI, 68-91%)) and TRUFFLE (77% (95% CI, 70-84%)), and was highest in pregnancies monitored using cCTG and DV Doppler (84% (95% CI, 80-89%)) (P < 0.01 for trend).

CONCLUSIONS

This analysis supports the hypothesis that the optimal method for fetal monitoring in pregnancies complicated by early-onset FGR is a combination of cCTG and DV Doppler assessment.

TRIAL REGISTRATION

GRIT ISRCTN41358726 and TRUFFLE ISRCTN56204499. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Computerized fetal cardiotocography analysis in early preterm fetal growth restriction - a quantitative comparison of two applications

Background We developed an open-source software for the computerized analysis of antenatal fetal cardiotocography (CTG) without limitation of duration of the registration, enabling batch processing and adaptation to any digital storage system. Methods STVcalc was developed based on literature about the FetalCare system (Huntleigh Healthcare Ltd, Cardiff, UK). For comparison with FetalCare, we selected the CTGs of all women who delivered in 2011 a small-for-gestational-age (SGA) fetus between 24 and 31 weeks by cesarean section (CS) for fetal distress, or had fetal death, before labor onset. Results In 471 CTGs from 39 women, the agreement was 99% for a short-term variation (STV) cut-off of 2.6 ms below 29 weeks and 3.0 ms thereafter, and 95% for 3.5 and 4.0 ms, respectively. In 18 (4%) cases, the proportional difference in STV between FetalCare and STVcalc was more than 10%. Conclusion As only slight differences were observed between the proposed feature-rich application and the FetalCare system, it can be considered valuable for clinical practice and research purposes.

Fetal heart rate monitoring and neonatal outcome in a population of early- and late-onset intrauterine growth restriction

AIM

The early-onset intrauterine growth restriction (IUGR) is associated with severe placental insufficiency and Doppler abnormalities. The late-onset IUGR is associated with mild placental insufficiency and normal Doppler velocimetry. The computerized cardiotocographic (cCTG) monitoring is used to evaluate the fetal well-being in pregnancies complicated by IUGR. Our aim was to investigate the cardiotocographic characteristics of IUGR fetuses and to identify every cCTG difference between Healthy and IUGR fetuses.

METHODS

Four hundred thirty pregnant women were enrolled starting from the 28th week of gestation until the time of delivery: 200 healthy and 230 IUGR fetuses. Fetal heart rate (FHR) baseline (FHR), short-term variability (STV), long-term irregularity (LTI), delta, interval index (II), approximate entropy (ApEn), high frequency (HF), low frequency (LF), movement frequency (MF), LF/(HF + MF) ratio (LF/(HF + MF)) and number of decelerations were examined. Newborn baby data were also collected.

RESULTS

The parameters of short- and medium-term variability discriminate between IUGR and healthy fetuses before 36 weeks including FHR, STV, LTI and delta discriminate between each subgroup of IUGR were compared to each one of the other two (P < 0.05).

CONCLUSION

cCTG is a useful tool for the evaluation of chronic hypoxemia, which causes a delay in the maturation of all components of the autonomic and central nervous system. However, cCTG requires integration with fetal ultrasound and Doppler vessels evaluation to improve the ability to predict the neonatal outcome.

The prognostic accuracy of short term variation of fetal heart rate in early-onset fetal growth restriction: A systematic review

OBJECTIVE

Cardiotocography (CTG) is an important tool for fetal surveillance in severe early-onset fetal growth restriction (FGR). Assessment of the CTG is usually performed visually (vCTG). However, it is suggested that computerized analysis of the CTG (cCTG) including short term variability (STV) could more accurately detect fetal compromise. The objective of this study was to systematically review the literature on the association between cCTG and perinatal outcome and the comparison of cCTG with vCTG.

STUDY DESIGN

A systematic search was performed in MEDLINE, EMBASE and Google Scholar. Studies were included that assessed prognostic accuracy of STV or compared STV to vCTG in patients with FGR. Risk of bias and concerns about applicability were assessed with the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) instrument.

RESULTS

Of the 885 records identified in the search, five cohort studies (387 patients) were included. We found no randomized studies comparing STV with visual CTG in patients with FGR. The risk of bias of all studies was generally judged as 'low'. One small study found an association of low STV with neonatal acidosis. One study observed no association of STV with long-term outcome. Composite analysis of all five studies showed a non-significant relative risk for acidosis after a low STV of 1.4 (95% CI 0.6-3.2, N = 387). Further meta-analysis was hampered due to heterogeneity in outcome reporting and use of different thresholds.

CONCLUSION

The evidence from the included studies did not support an association of STV and short or long term outcome. However, available data are limited and heterogeneous, and influenced by management based on STV. Solid evidence from a randomized controlled trial comparing STV with vCTG including long term infant outcome is needed before STV can be used clinically for timing of delivery in patients with FGR.

A Comprehensive Evaluation of the Predictive Abilities of Fetal Electrocardiogram-Derived Parameters during Labor in Newborn Acidemia: Our Institutional Experience

This study aimed to identify cardiotocography patterns that discriminate fetal acidemia newborns by comprehensively evaluating the parameters obtained from Holter monitoring during delivery. Between June 1, 2015, and August 1, 2016, a prospective observational study of 85 patients was conducted using fetal Holter monitoring at the Beijing Obstetrics and Gynecology Hospital, Capital Medical University, China. Umbilical cord blood was sampled immediately after delivery and fetal acidemia was defined as umbilical cord arterial blood pH < 7.20. Fetal electrocardiogram- (FECG-) derived parameters, including basal fetal heart rate (BFHR), short-term variation (STV), large acceleration (LA), deceleration capacity (DC), acceleration capacity (AC), proportion of episodes of high variation (PEHV), and proportion of episodes of low variation (PELV), were compared between 16 fetuses with acidemia and 47 without. The areas under the curve (AUC) of receiver operating characteristics (ROC) were calculated. Although all the computerized parameters showed predictive values for acidemia (all AUC > 0.50), STV (AUC = 0.84, P < 0.001), DC (AUC = 0.84, P < 0.001), AC (AUC = 0.80, P < 0.001), and PELV (AUC = 0.71, P = 0.012) were more strongly associated with fetal acidemia. Our institutional experience suggests that FECG-derived parameters from Holter monitoring are beneficial in reducing the incidence of neonatal acidemia.