Fetal electrocardiogram: ST waveform analysis in intrapartum surveillance

Fetal Heart Rate Preprocessing Techniques: A Scoping Review

Monitoring fetal heart rate (FHR) through cardiotocography is crucial for the early diagnosis of fetal distress situations, necessitating prompt obstetrical intervention. However, FHR signals are often marred by various contaminants, making preprocessing techniques essential for accurate analysis. This scoping review, following PRISMA-ScR guidelines, describes the preprocessing methods in original research articles on human FHR (or beat-to-beat intervals) signal preprocessing from PubMed and Web of Science, published from their inception up to May 2021. From the 322 unique articles identified, 54 were included, from which prevalent preprocessing approaches were identified, primarily focusing on the detection and correction of poor signal quality events. Detection usually entailed analyzing deviations from neighboring samples, whereas correction often relied on interpolation techniques. It was also noted that there is a lack of consensus regarding the definition of missing samples, outliers, and artifacts. Trends indicate a surge in research interest in the decade 2011-2021. This review underscores the need for standardizing FHR signal preprocessing techniques to enhance diagnostic accuracy. Future work should focus on applying and evaluating these methods across FHR databases aiming to assess their effectiveness and propose improvements.

Fetal monitoring technologies for the detection of intrapartum hypoxia - challenges and opportunities

Intrapartum fetal hypoxia is related to long-term morbidity and mortality of the fetus and the mother. Fetal surveillance is extremely important to minimize the adverse outcomes arising from fetal hypoxia during labour. Several methods have been used in current clinical practice to monitor fetal well-being. For instance, biophysical technologies including cardiotocography, ST-analysis adjunct to cardiotocography, and Doppler ultrasound are used for intrapartum fetal monitoring. However, these technologies result in a high false-positive rate and increased obstetric interventions during labour. Alternatively, biochemical-based technologies including fetal scalp blood sampling and fetal pulse oximetry are used to identify metabolic acidosis and oxygen deprivation resulting from fetal hypoxia. These technologies neither improve clinical outcomes nor reduce unnecessary interventions during labour. Also, there is a need to link the physiological changes during fetal hypoxia to fetal monitoring technologies. The objective of this article is to assess the clinical background of fetal hypoxia and to review existing monitoring technologies for the detection and monitoring of fetal hypoxia. A comprehensive review has been made to predict fetal hypoxia using computational and machine-learning algorithms. The detection of more specific biomarkers or new sensing technologies is also reviewed which may help in the enhancement of the reliability of continuous fetal monitoring and may result in the accurate detection of intrapartum fetal hypoxia.

Is the fetus fit for labor? Introducing fast-and-frugal trees (FFTrees) to simplify triage of women for STAN monitoring: An interobserver agreement comparison with traditional classification

INTRODUCTION

It is a shortcoming of traditional cardiotocography (CTG) classification table formats that CTG traces are frequently classified differently by different users, resulting in poor interobserver agreements. A fast-and-frugal tree (FFTree) flow chart may help provide better concordance because it is straightforward and has clearly structured binary questions with understandable "yes" or "no" responses. The initial triage to determine whether a fetus is suitable for labor when utilizing fetal ECG ST analysis (STAN) is very important, since a fetus with restricted capacity to respond to hypoxic stress may not generate STAN events and therefore may become falsely negative. This study aimed to compare physiology-focused FFTree CTG interpretation with FIGO classification for assessing the suitability for STAN monitoring.

MATERIAL AND METHODS

A retrospective study of 36 CTG traces with a high proportion of adverse outcomes (17/36) selected from a European multicenter study database. Eight experienced European obstetricians evaluated the initial 40 minutes of the CTG recordings and judged whether STAN was a suitable fetal surveillance method and whether intervention was indicated. The experts rated the CTGs using the FFTree and FIGO classifications at least 6 weeks apart. Interobserver agreements were calculated using proportions of agreement and Fleiss' kappa (κ).

RESULTS

The proportions of agreement for "not suitable for STAN" were for FIGO 47% (95% confidence interval [CI] 42%-52%) and for FFTree 60% (95% CI 56-64), ie a significant difference; the corresponding figures for "yes, suitable" were 74% (95% CI 71-77) and 70% (95% CI 67-74). For "intervention needed" the figures were 52% (95% CI 47-56) vs 58% (95% CI 54-62) and for "expectant management" 74% (95% CI 71-77) vs 72% (95% CI 69-75). Fleiss' κ agreement on "suitability for STAN" was 0.50 (95% CI 0.44-0.56) for the FIGO classification and 0.57 (95% CI 0.51-0.63) for the FFTree classification; the corresponding figures for "intervention or expectancy" were 0.53 (95% CI 0.47-0.59) and 0.57 (95% CI 0.51-0.63).

CONCLUSIONS

The proportion of agreement among expert obstetricians using the FFTree physiological approach was significantly higher compared with the traditional FIGO classification system in rejecting cases not suitable for STAN monitoring. That might be of importance to avoid false negative STAN recordings. Other agreement figures were similar. It remains to be shown whether the FFTree simplicity will benefit less experienced users and how it will work in real-world clinical scenarios.

Sporadic accelerations during labor strongly indicate normal pH, whereas periodic accelerations do not: a case-control study

PURPOSE

To determine the association between the occurrence of sporadic and periodic fetal heart rate accelerations during labor and acidemia at birth.

MATERIALS AND METHODS

This is a case-control study of fetal heart rate patterns from 364 neonates with acidemia at birth (cord blood pH <7.05 at vaginal birth, or pH <7.10 at birth after first stage cesarean delivery) and 731 controls with pH ≥7.15. The last 30-60 min of the cardiotocographic traces before birth from the neonates born with acidemia and from the corresponding stage in labor for the controls were scrutinized. Odds ratios (OR) with 95% confidence interval for acidemia at birth were determined.

RESULTS

During the first stage, ≥2 sporadic accelerations were present in 16% of cases and 78% of controls; OR for acidemia (compared to 0-1 accelerations) 0.05 (0.02-0.10). In the second stage, the corresponding rates were 13% and 60%, OR 0.09 (0.06-0.14). Isolated periodic accelerations were infrequent. A weak negative association between ≥2 periodic accelerations and acidemia (compared with 0-1 accelerations) was found in the second stage, OR 0.51 (0.30-0.86), but was not significant in the first stage, OR 0.24 (0.04-1.4). Even among fetuses with normal fetal heart rate variability (5-25 beats per minute) the occurrence of less than two sporadic accelerations was associated with an increased risk of acidemia, OR 10.3 (7.2-14.8).

CONCLUSIONS

Sporadic accelerations indicate a very low probability of acidosis but are absent in 40% of fetuses with normal pH during a 30-60 min second-stage recording.

Prevalence, birth, and clinical characteristics of dyskinetic cerebral palsy compared with spastic cerebral palsy subtypes: A Norwegian register-based study

AIM

To study the prevalence, birth, and clinical characteristics of children with dyskinetic cerebral palsy (CP) in Norway compared with spastic quadriplegic CP and other spastic CP subtypes.

METHOD

Data on children born from 1996 to 2015 were collected from the Norwegian Quality and Surveillance Registry for Cerebral Palsy and the Medical Birth Registry of Norway.

RESULTS

One hundred and seventy (6.8%) children had dyskinetic CP. The birth prevalence decreased during 1996 to 2015 from 0.21 to 0.07 per 1000 livebirths (p < 0.001). Dyskinetic CP was more often associated with term/post-term birth, and motor and associated impairments were more severe compared with spastic bilateral and unilateral CP, but less severe than spastic quadriplegic CP. On neuroimaging, grey matter injuries were most prevalent in dyskinetic CP (mainly basal ganglia/thalamus) and spastic quadriplegic CP (mainly cortico-subcortical), white matter injuries in spastic bilateral, and white and grey matter injuries were equally common in spastic unilateral CP. Normal neuroimaging and brain maldevelopment were present in 25% of children with dyskinetic CP.

INTERPRETATION

The decrease in birth prevalence of dyskinetic CP was probably due to improved antenatal and perinatal care. Potential sentinel events at term were more common in dyskinetic CP than other spastic CP subtypes. However, probable antenatal aetiologies were most prevalent. Motor and associated impairments were less severe in children with dyskinetic CP compared with spastic quadriplegic CP.

WHAT THIS PAPER ADDS

Birth prevalence of those with dyskinetic and spastic bilateral cerebral palsy (CP) in Norway decreased between 1996 and 2015. Potential sentinel events at term were more common in dyskinetic CP. Nonetheless, probable antenatal aetiologies were most prevalent in dyskinetic CP. Basal ganglia/thalamus lesions were more common in dyskinetic than spastic quadriplegic CP. Motor and associated impairments were milder in dyskinetic than spastic quadriplegic CP.

Comparison of effect of CTG + STan with CTG alone on emergency Cesarean section rate: STan Australian Randomized controlled Trial (START)

OBJECTIVE

To investigate whether use of ST analysis of the fetal electrocardiogram (STan) as an adjunct to continuous cardiotocography (CTG) reduces the rate of emergency Cesarean section (EmCS) compared with CTG alone.

METHODS

This was a randomized controlled trial of patients with a singleton fetus in cephalic presentation at ≥ 36 weeks' gestation, requiring continuous electronic fetal monitoring during labor at a tertiary maternity hospital in Adelaide, Australia, between January 2018 and July 2021. Participants were randomized to undergo CTG + STan or CTG alone. The calculated sample size was 1818 participants. The primary outcome was EmCS. Secondary outcomes included metabolic acidosis, a composite adverse perinatal outcome, and other maternal and neonatal morbidity and safety outcomes.

RESULTS

The present study enrolled 970 women, of whom 967 were included in the primary analysis. EmCS occurred in 107/482 (22.2%) deliveries in the CTG + STan arm and in 107/485 (22.1%) in the CTG arm (adjusted relative risk, 1.02 (95% CI, 0.81-1.27); P = 0.89). There was no difference in the rate of adverse maternal or neonatal outcomes between arms.

CONCLUSIONS

The addition of STan as an adjunct to continuous CTG did not reduce the EmCS rate. The smaller-than-anticipated sample size meant that this study was underpowered to detect absolute differences of ≤ 5% and, therefore, this negative finding could be due to a Type-2 error. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Adapted ST analysis during labor: relative versus absolute ST events, a case-control study

BACKGROUND

The value of ST analysis of the fetal electrocardiogram during labor to lower asphyxia and cesarean section rates is uncertain. Physiological variation of the electrical heart axis between fetuses may explain false alarms in conventional ST analysis (absolute ST analysis). ST events (alarms) based on relative T/QRS rises (relative ST analysis) correct for this variation and may improve diagnostic accuracy of ST analysis.

AIMS

To compare the diagnostic accuracy of absolute and relative ST analysis with regard to fetal acidemia.

STUDY DESIGN

Retrospective case-control study.

SUBJECTS

20 healthy women with an uncomplicated pregnancy monitored with ST analysis during labor: 10 cases (umbilical cord artery pH < 7.05) and 10 controls (pH > 7.20).

OUTCOME MEASURES

Sensitivity, specificity, positive and negative likelihood ratio.

RESULTS

In 16 of the 20 patients a total of 54 absolute ST events were reported. Two reviewers classified the cardiotocograms; in cases 29% of the absolute ST events were significant, in the controls it was 19%. Relative ST analysis versus absolute ST analysis showed a sensitivity of 90% (55-100%) vs. 70% (35-93%), a specificity of 100% (69-100%) vs. 70% (35-93%), a positive likelihood ratio of infinity vs. 2.3 (0.8-6.5), a negative likelihood ratio of 0.1 (0.0-0.6) vs. 0.4 (0.2-1.2), and diagnostic odds ratio of infinity vs. 5.4 (0.8-36.9). McNemar showed no statistical significant difference between the sensitivity and specificity of the methods.

CONCLUSIONS

We observed higher positive and lower negative likelihood ratios for relative ST analysis in comparison to absolute ST analysis. In this small study we found no statistical difference. Relative ST analysis should be studied in a larger study.

Time to reconsider: Have the 2015 FIGO and 2017 Swedish intrapartum cardiotocogram classifications led us from Charybdis to Scylla?

In 2015, FIGO revised the 1987 intrapartum cardiotocography (CTG) classification (FIGO1987). A less radical FIGO2015 version was introduced in Sweden 2017 (SWE2017). Now, post hoc simulation studies show that FIGO2015 and SWE2017 are less reliable than (a modified) FIGO1987. FIGO2015 shows significantly better interobserver agreement for normal CTG traces than FIGO1987, but significantly worse for pathological traces. Agreements between templates are moderate to good, but different classifications of mainly variable decelerations and tachycardia cause significant heterogeneities. FIGO2015 shows insufficient sensitivity to identify fetal acidemia compared with FIGO1987. In connection with fetal electrocardiogram ST analysis, one study showed no template was superior in identifying fetal acidemia, but in a series of only academia, FIGO1987 had significantly higher sensitivity than FIGO2015 (73% vs. 43%) and set of an alarm for fetal acidemia considerably earlier. With SWE2017, operative interventions declined significantly in Sweden but several adverse neonatal outcomes increased significantly. It remains to investigate the development with FIGO2015.

Monitoring fetal well-being in labor in late fetal growth restriction

Late-onset fetal growth restriction (FGR) accounts for approximately 70-80% of all cases of FGR secondary to uteroplacental insufficiency. It is associated with an increased incidence of adverse antepartum and perinatal events, which in most instances result from hypoxic insults either present at the onset of labor or supervening during labor as a result of uterine contractions. Labor represents a stressful event for the fetoplacental unit being uterine contractions associated with an up-to 60% reduction of the uteroplacental perfusion. Intrapartum fetal heart rate monitoring by means of cardiotocography (CTG) currently represents the mainstay for the identification of fetal hypoxia during labor and is recommended for the fetal surveillance during labor in the case of FGR or other conditions associated with an increased risk of intrapartum hypoxia. In this review we discuss the potential implications of an impaired placental function on the intrapartum adaptation to the hypoxic stress and the role of the CTG and alternative techniques for the intrapartum monitoring of the fetal wellbeing in the context of FGR secondary to uteroplacental insufficiency.

STAN: a reappraisal of its clinical usefulness

The automatic analysis of fetal ECG in labor has been introduced as an adjunct of traditional cardiotocography with the aim to improve the identification of fetuses with intrapartum hypoxia. Several randomized controlled trials and meta-analyses have produced conflicting results, with the most recent randomized controlled trial not demonstrating any improvement in either neonatal outcomes or reduction in operative birth rates. The objective of this review article is to present the state of art about the use of STAN technology in labor ward.

Impaired validity of the new FIGO and Swedish CTG classification templates to identify fetal acidosis in the first stage of labor

INTRODUCTION

Cardiotocography (CTG) is the main method of intrapartum fetal surveillance. In 2015 a new guideline was introduced by the International Federation of Gynecology and Obstetrics (FIGO), FIGO-15. In Sweden it was adjusted to SWE-17, replacing the previous national template, SWE-09. This study, conducted at one university hospital and one regional hospital in southern Sweden, evaluated the diagnostic validity of these three templates to detect fetal acidosis during the first stage of labor.

MATERIAL AND METHODS

A total of 73 neonates with pH <7.1 in umbilical cord artery or vein at cesarean delivery during the first stage of labor were identified retrospectively. For each acidotic neonate, three non-acidemic neonates, with a pH ≥7.2 in cord artery and vein, and Apgar scores ≥9 at five and ten minutes, in all 219 neonates, were selected. The CTG tracings before birth in acidemic neonates, and tracings at the same cervical dilatation in the non-acidemic neonates, were independently assessed by three professionals from the obstetric staff, blinded to group and clinical data. Based on their categorizations of the included variables (baseline, variability, accelerations, decelerations and contraction rate), each CTG tracing was systematically classified according to the three templates. The sensitivity and specificity to identify acidemia by the classification pathological were determined for each template. Interobserver agreement in the assessments of tracings as pathological or not was analyzed, using free-marginal Kappa index.

RESULTS

The sensitivity for patterns classified as pathological to identify acidemia was similar for FIGO-15 (71%) and SWE-17 (77%, p = .13), and the specificity was 97% for both. SWE-09 had a significantly higher sensitivity (95%, p < .001) albeit with a lower specificity (90%, p < .001) than the other two templates. Among acidemic neonates, the fraction of tracings classified as normal was higher with SWE-17 (9.6%) than with SWE-09 (0%; p = .01) and FIGO-15 (1.4%; p = .06). For tracings from neonates with acidemia, agreement for three independent assessors was strong (κ 0.85) with SWE-09, and weak for FIGO-15 (κ 0.47), and SWE-17 (κ 0.51). For tracings from neonates without acidemia, the agreement was almost perfect for FIGO-15 (κ 0.91), strong withSWE-17 (κ 0.90) and moderate with SWE-09 (κ 0.78).

CONCLUSIONS

The ability of FIGO-15 and SWE-17 to identify fetal acidosis is considered insufficient. The combination of a high sensitivity and a high specificity makes SWE-09 the most discriminatory template during the first stage of labor.

Comparing the effect of STan (cardiotocographic electronic fetal monitoring (CTG) plus analysis of the ST segment of the fetal electrocardiogram) with CTG alone on emergency caesarean section rates: study protocol for the STan Australian Randomised controlled Trial (START)

BACKGROUND

Cardiotocography is almost ubiquitous in its use in intrapartum care. Although it has been demonstrated that there is some benefit from continuous intrapartum fetal monitoring using cardiotocography, there is also an increased risk of caesarean section which is accompanied by short-term and long-term risks to the mother and child. There is considerable potential to reduce unnecessary operative delivery with up to a 60% false positive diagnosis of fetal distress using cardiotocography alone. ST analysis of the fetal electrocardiogram is a promising adjunct to cardiotocography alone, and permits detection of metabolic acidosis of the fetus, potentially reducing false positive diagnosis of fetal distress.

METHODS

This study will be a single-centre, parallel-group, randomised controlled trial, conducted over 3 years. The primary hypothesis will be that the proportion of women with an emergency caesarean section on ST analysis will not equal that for women on cardiotocography monitoring alone. Participants will be recruited at the Women's and Children's Hospital, a high-risk specialty facility with approximately 5000 deliveries per annum. A total of 1818 women will be randomised to the treatment or conventional arm with an allocation ratio of 1:1, stratified by parity. The primary outcome is emergency caesarean section (yes/no). Statistical analysis will follow standard methods for randomised trials and will be performed on an intention-to-treat basis. Secondary maternal and neonatal outcomes will also be analysed. Additional study outcomes include psychosocial outcomes, patient preferences and cost-effectiveness.

DISCUSSION

Approximately 20% of Australian babies are delivered by emergency caesarean section. This will be the first Australian trial to examine ST analysis of the fetal electrocardiogram as an adjunct to cardiotocography as a potential method for reducing this proportion. The trial will be among the first to comprehensively examine ST analysis, taking into account the impact on psychosocial well-being as well as cost-effectiveness. This research will provide Australian evidence for clinical practice and guideline development as well as for policy-makers and consumers to make informed, evidence-based choices about care in labour.

TRIAL REGISTRATION

ANZCTR, ACTRN1261800006268 . Registered on 19 January 2018.

Significant reduction in umbilical artery metabolic acidosis after implementation of intrapartum ST waveform analysis of the fetal electrocardiogram

BACKGROUND

Although the evidence regarding the benefit of using ST waveform analysis of the fetal electrocardiogram is conflicting, ST waveform analysis is considered as adjunct to identify fetuses at risk for asphyxia in our center. Most randomized controlled trials and meta-analyses have not shown a significant decrease in umbilical metabolic acidosis, while some observational studies have shown a gradual decrease of this outcome over a longer period of time. Observational studies can give more insight into the effect of implementation of the ST technology in daily clinical practice.

OBJECTIVE

To evaluate the change in frequency of perinatal intervention and adverse neonatal outcome after the implementation of ST waveform analysis of the fetal electrocardiogram from 2000 to 2013.

STUDY DESIGN

This retrospective longitudinal study was conducted in a tertiary referral center. A total of 19,664 medium- and high-risk singleton pregnancies with fetuses in cephalic presentation, a gestational age of ≥36 weeks, and the intention to deliver vaginally were included. ST waveform analysis of the fetal electrocardiogram was implemented in the year 2000 and by 2010 all deliveries were monitored using this technology. Data were collected on the following perinatal outcomes: fetal blood sampling, mode of delivery, umbilical cord blood gases, Apgar scores, neonatal encephalopathy, and perinatal death. Longitudinal trend analysis was used to detect changes over time in all deliveries monitored by cardiotocography either alone or in adjunct to ST waveform analysis of the fetal electrocardiogram. Logistic regression was used to correct for possible confounders.

RESULTS

The umbilical artery metabolic acidosis rate declined from 2.5% (average rate of 2000 + 2001 + 2002) to 0.4% (average of 2011 + 2012 + 2013) (P < .001), which represents an 84% decrease. This decrease largely occurred between 2006 and 2008, during the Dutch randomized trial on fetal electrocardiogram ST waveform analysis. At this time, approximately 20% of deliveries were monitored using this method. Furthermore, there were significant reductions in fetal blood sampling rate (P < .001). Overall cesarean and vaginal instrumental deliveries decreased significantly (P < .001), but not for fetal distress. There were no changes in the Apgar scores. The incidence of neonatal encephalopathy was significantly lower in the second part of the study (odds ratio 0.39, 95% confidence interval 0.17-0.89).

CONCLUSION

There was an 84% decrease in the incidence of umbilical artery metabolic acidosis in all deliveries between 2000 and 2013. The neonatal encephalopathy rate, fetal blood sampling rate, and the total number of cesarean and vaginal instrumental deliveries also decreased.

Biomarkers of impaired placentation at 35-37 weeks' gestation in the prediction of adverse perinatal outcome

OBJECTIVE

To investigate the potential value of uterine artery pulsatility index (UtA-PI) and serum levels of the angiogenic placental growth factor (PlGF) and the antiangiogenic factor soluble fms-like tyrosine kinase-1 (sFlt-1) in the prediction of adverse perinatal outcome in small-for-gestational-age (SGA) and non-SGA neonates at 35-37 weeks' gestation.

METHODS

This was a prospective observational study of 19 209 singleton pregnancies attending for a routine hospital visit at 35 + 0 to 36 + 6 weeks' gestation. This visit included recording of maternal demographic characteristics and medical history, sonographic estimation of fetal weight, color Doppler ultrasound for measurement of mean UtA-PI, and measurement of serum concentrations of PlGF and sFlt-1. Multivariable logistic regression analysis was carried out to determine which of the factors from maternal or pregnancy characteristics and measurements of UtA-PI, PlGF and sFlt-1 provided a significant contribution in the prediction of each of four adverse outcome measures: first, stillbirth; second, Cesarean delivery for suspected fetal compromise in labor; third, neonatal death or hypoxic ischemic encephalopathy Grade 2 or 3; and, fourth, admission to the neonatal unit (NNU) for ≥ 48 h. Predicted probabilities from logistic regression analysis were used to construct receiver-operating characteristics curves to assess the performance of screening for these adverse outcomes.

RESULTS

First, 83% of stillbirths, 82% of Cesarean sections for presumed fetal compromise in labor, 91% of cases of neonatal death or hypoxic ischemic encephalopathy and 86% of NNU admissions for ≥ 48 h occurred in pregnancies with a non-SGA neonate. Second, UtA-PI > 95^th percentile, sFlt-1 > 95^th percentile and PlGF < 5^th percentile were associated with increased risk of Cesarean delivery for suspected fetal compromise in labor and NNU admission for ≥ 48 h; the number of stillbirths and cases of neonatal death or hypoxic ischemic encephalopathy was too small to demonstrate significance in the observed differences from cases without these adverse outcomes. Third, multivariable logistic regression analysis demonstrated that, in the prediction of Cesarean delivery for suspected fetal compromise in labor, there was no significant contribution from biomarkers; the prediction of NNU admission for ≥ 48 h by maternal demographic characteristics and medical history was only marginally improved by the addition of sFlt-1 or PlGF. Fourth, for each biomarker, the detection rate of adverse outcome was higher in SGA than in non-SGA neonates, but this increase was accompanied by an increase in false-positive rate. Fifth, the relative risk of UtA-PI > 95^th , sFlt-1 > 95^th and PlGF < 5^th percentiles for most adverse outcomes was < 2.5 in both SGA and non-SGA neonates.

CONCLUSIONS

In pregnancies undergoing routine antenatal assessment at 35-37 weeks' gestation, measurements of UtA-PI, sFlt-1 or PlGF provide poor prediction of adverse perinatal outcome in both SGA and non-SGA fetuses. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Routine assessment of cerebroplacental ratio at 35-37 weeks' gestation in the prediction of adverse perinatal outcome

BACKGROUND

Third-trimester studies in selected high-risk pregnancies have reported that low cerebroplacental ratio, due to high pulsatility index in the umbilical artery, and or decreased pulsatility index in the fetal middle cerebral artery, is associated with increased risk of adverse perinatal outcomes.

OBJECTIVE

To investigate the predictive performance of screening for adverse perinatal outcome by the cerebroplacental ratio measured routinely at 35-37 weeks' gestation.

STUDY DESIGN

This was a prospective observational study in 47,211 women with singleton pregnancies undergoing routine ultrasound examination at 35⁺⁶ to 37⁺⁶ weeks' gestation, including measurement of umbilical artery-pulsatility index and middle cerebral artery-pulsatility index. The measured umbilical artery-pulsatility index and middle cerebral artery-pulsatility index and their ratio were converted to multiples of the median after adjustment for gestational age. Multivariable logistic regression analysis was used to determine whether umbilical artery-pulsatility index, middle cerebral artery-pulsatility index, and cerebroplacental ratio improved the prediction of adverse perinatal outcome that was provided by maternal characteristics, medical history, and obstetric factors. The following outcome measures were considered: (1) adverse perinatal outcome consisting of stillbirth, neonatal death, or hypoxic-ischemic encephalopathy grades 2 and 3; (2) presence of surrogate markers of perinatal hypoxia consisting of umbilical arterial or venous cord blood pH ≤7 and ≤7.1, respectively, 5-minute Apgar score <7, or admission to the neonatal intensive care unit for >24 hours; (3) cesarean delivery for presumed fetal compromise in labor; and (4) neonatal birthweight less than the third percentile for gestational age.

RESULTS

First, the incidence of adverse perinatal outcome, presence of surrogate markers of perinatal hypoxia, and cesarean delivery for presumed fetal compromise in labor was greater in pregnancies with small for gestational age neonates with birthweight <10th percentile compared with appropriate for gestational age neonates; however, 80%-85% of these adverse events occurred in the appropriate for gestational age group. Second, low cerebroplacental ratio <10th percentile was associated with increased risk of adverse perinatal outcome, presence of surrogate markers of perinatal hypoxia, cesarean delivery for presumed fetal compromise in labor, and birth of neonates with birthweight less than third percentile. However, multivariable regression analysis demonstrated that the prediction of these adverse outcomes by maternal demographic characteristics and medical history was only marginally improved by the addition of cerebroplacental ratio. Third, the performance of low cerebroplacental ratio in the prediction of each adverse outcome was poor, with detection rates of 13%-26% and a false-positive rate of about 10%. Fourth, the detection rates of adverse outcomes were greater in small for gestational age than in appropriate for gestational age babies and in pregnancies delivering within 2 weeks rather than at any stage after assessment; however, such increase in detection rates was accompanied by an increase in the false-positive rate. Fifth, in appropriate for gestational age neonates, the predictive accuracy of cerebroplacental ratio was low, with positive and negative likelihood ratios ranging from 1.21 to 1.82, and 0.92 to 0.98, respectively; although the accuracy was better in small for gestational age neonates, this was also low with positive likelihood ratios of 1.31-2.26 and negative likelihood ratios of 0.69-0.92. Similar values were obtained in fetuses classified as small for gestational age and appropriate for gestational age according to the estimated fetal weight.

CONCLUSIONS

In pregnancies undergoing routine antenatal assessment at 35-37 weeks' gestation, measurement of cerebroplacental ratio provides poor prediction of adverse perinatal outcome in both small for gestational age and appropriate for gestational age fetuses.

Relative versus absolute rises in T/QRS ratio by ST analysis of fetal electrocardiograms in labour: A case-control pilot study

Introduction

The additional value of ST analysis during labour is uncertain. In ST analysis, a T/QRS baseline value is calculated from the fetal electrocardiogram and successive T/QRS ratios are compared to this baseline. However, variation in the orientation of the electrical heart axis between fetuses may yield different T/QRS baseline values. In case of a higher T/QRS baseline value more ST events are encountered, although not always related to perinatal outcome. We hypothesised that we can partly correct for this effect by analysing T/QRS rises as a percentage from baseline (relative ST analysis). This study aimed to explore whether relative ST analysis has better diagnostic value for cord acidaemia compared to conventional ST analysis, where predefined fixed T/QRS ratios are used.

Methods and materials

A case-control study was performed in 20 term human fetuses during labour; 10 cases (umbilical cord artery pH <7.05 at birth, defining acidaemia) and 10 controls (pH >7.20) were included. The fetal electrocardiogram was recorded using a STAN monitor. We electronically extracted all T/QRS values, baseline and episodic ST events from the STAN monitor and calculated the relative T/QRS changes. The cut-off for relative ST events was determined in a receiver operator characteristic (ROC) curve at optimal specificity for cord acidaemia. Parameters of interest were area under the curve (AUC) of the ROC curve for relative ST events and test performance of both conventional and relative ST analysis.

Results

Relative ST analysis showed an AUC of 0.99. The optimal cut-off value for relative T/QRS rise was determined at 0.70. Relative vs conventional (absolute) ST analysis showed a specificity of 100% vs 40% (p = 0.031); sensitivity 90% vs 90%; positive likelihood ratio infinity vs 1.5; negative likelihood ratio 0.10 vs 0.25, respectively.

Conclusion

Relative ST analysis seems to be a promising method to detect impending fetal acidaemia during labour. Further studies are required to determine the diagnostic accuracy.

Computerized analysis of cardiotocograms and ST signals is associated with significant reductions in hypoxic-ischemic encephalopathy and cesarean delivery: an observational study in 38,466 deliveries

BACKGROUND

Intrapartum cardiotocography is widely used in high-resource countries and remains at the center of fetal monitoring and the decision to intervene, but there is ample evidence of poor reliability in visual interpretation as well as limited accuracy in identifying fetal hypoxia. Combined monitoring of intrapartum cardiotocography and ST segment signals was developed to increase specificity, but analysis relies heavily on intrapartum cardiotocography interpretation and is therefore also affected by the previously referred problems. Computerized analysis was developed to overcome these limitations, aiding in the quantification of parameters that are difficult to evaluate visually, such as variability, integrating the complex guidelines of combined intrapartum cardiotocography and ST analysis, and using visual and sound alerts to prompt health care professionals to reevaluate features associated with fetal hypoxia.

OBJECTIVE

The objective of the study was to evaluate the effect of introducing a central fetal monitoring system with computerized analysis of intrapartum cardiotocography and ST signals into the labor ward of a tertiary care university hospital in which all women are continuously monitored with intrapartum cardiotocography. The incidence of adverse perinatal outcomes and intervention rates was evaluated over time.

STUDY DESIGN

In this retrospective cohort study, yearly rates of hypoxic-ischemic encephalopathy, instrumental vaginal delivery, overall cesarean delivery, and urgent cesarean delivery were obtained from the hospital's clinical databases. The rates occurring in the period from January 2001 to December 2003, before the introduction of the central monitoring system with computerized analysis of intrapartum cardiotocography and ST signals (Omniview-SisPorto), were compared with those occurring from January 2004 to December 2014, after the introduction of the system. All rates were calculated with 95% confidence intervals.

RESULTS

A total of 38,466 deliveries occurred during this period. After introduction of the system, there was a significant decrease in the number of hypoxic-ischemic encephalopathy cases per 1000 births (5.3%, 95% confidence interval [4.0-7.0] vs 2.2%, 95% confidence interval [1.7-2.8]; relative risk, 0.42, 95% confidence interval [0.29-0.61]), overall cesarean delivery rates (29.9%, 95% confidence interval [28.9-30.8] vs 28.3%, 95% confidence interval [27.8-28.8]; relative risk, 0.96, 95% confidence interval [0.92-0.99]), and urgent cesarean deliveries (21.6%, 95% confidence interval [20.7-22.4] vs 19.2%, 95% confidence interval [18.8-19.7]; relative risk, 0.91, 95% confidence interval [0.87-0.95]). The instrumental vaginal delivery rate increased (19.5%, 95% confidence interval [18.7-20.3] vs 21.4%, 95% confidence interval [21.0-21.9; relative risk, 1.07, 95% confidence interval 1.02-1.13].

CONCLUSION

Introduction of computerized analysis of intrapartum cardiotocography and ST signals in a tertiary care hospital was associated with a significant reduction in the incidence of hypoxic-ischemic encephalopathy and a modest reduction in cesarean deliveries.

Cardiotocography alone vs. cardiotocography with ST segment analysis for intrapartum fetal monitoring in women with late-term pregnancy. A randomized controlled trial

OBJECTIVES

Randomized studies have obtained conflicting results regarding the usefulness of fetal electrocardiographic (ECG) ST-segment analysis, possibly because these studies included non-homogeneous populations. We designed a study to determine whether this monitoring technique is potentially useful for populations at risk for fetal heart rate alterations during labor, i.e. groups of women who share late-term pregnancy as a risk factor.

STUDY DESIGN

This randomized clinical trial recruited women whose pregnancy had lasted more than 290 days. The participants were randomly assigned to continuous fetal cardiotocographic monitoring alone (CTG group) or with fetal ECG ST-segment analysis (ECG-F group). In the CTG group fetal heart rate was interpreted according to guidelines from the National Institute of Child Health and Human Development, whereas in the ECG-F group the tracings were interpreted according the original International Federation of Gynecology and Obstetrics (FIGO) guidelines. The primary outcome measure was neonatal outcome, evaluated as arterial blood pH in neonates after abdominal or vaginal operative delivery indicated because of nonreassuring fetal status.

RESULTS

A total of 237 women were randomized, of whom 200 were included in the final analysis (100 in each group). The rate of cesarean delivery was the same in both groups (26%), and the rate of operative delivery due to nonreassuring fetal status did not differ significantly (38% in the CTG group vs. 39% in the ECG-F group). Regarding neonatal outcomes, there was no significant difference between groups in neonatal pH (7.27 [7.23-7.29] and 7.25 [7.21-7.27]).

CONCLUSIONS

In a population comprising only late-term pregnancies, fetal ECG monitoring had no benefits for the mother or fetus. Additional studies are needed of protocols for using ST waveform analysis in selected population groups.

New FIGO and Swedish intrapartum cardiotocography classification systems incorporated in the fetal ECG ST analysis (STAN) interpretation algorithm: agreements and discrepancies in cardiotocography classification and evaluation of significant ST events

Introduction

The updated intrapartum cardiotocography (CTG) classification system by FIGO in 2015 (FIGO2015) and the FIGO2015‐approached classification by the Swedish Society of Obstetricians and Gynecologist in 2017 (SSOG2017) are not harmonized with the fetal ECG ST analysis (STAN) algorithm from 2007 (STAN2007). The study aimed to reveal homogeneity and agreement between the systems in classifying CTG and ST events, and relate them to maternal and perinatal outcomes.

Material and methods

Among CTG traces with ST events, 100 traces originally classified as normal, 100 as suspicious and 100 as pathological were randomly selected from a STAN database and classified by two experts in consensus. Homogeneity and agreement statistics between the CTG classifications were performed. Maternal and perinatal outcomes were evaluated in cases with clinically hidden ST data (n = 151). A two‐tailed p < 0.05 was regarded as significant.

Results

For CTG classes, the heterogeneity was significant between the old and new systems, and agreements were moderate to strong (proportion of agreement, kappa index 0.70–0.86). Between the new classifications, heterogeneity was significant and agreements strong (0.90, 0.92). For significant ST events, heterogeneities were significant and agreements moderate to almost perfect (STAN2007 vs. FIGO2015 0.86, 0.72; STAN2007 vs. SSOG2017 0.92, 0.84; FIGO2015 vs. SSOG2017 0.94, 0.87). Significant ST events occurred more often combined with STAN2007 than with FIGO2015 classification, but not with SSOG2017; correct identification of adverse outcomes was not significantly different between the systems.

Conclusion

There are discrepancies in the classification of CTG patterns and significant ST events between the old and new systems. The clinical relevance of the findings remains to be shown.

Identifying newborns with umbilical cord blood metabolic acidosis by intrapartum cardiotography combined with fetal ECG ST analysis (STAN): comparison of the new and old FIGO systems to classify cardiotocograms

Introduction: The intrapartum cardiotocography (CTG) classification system by FIGO in 2015 (FIGO2015) was introduced to simplify CTG interpretation, but it is not harmonized with the fetal ECG ST analysis (STAN) algorithm from 2007 (STAN2007), which is based on the FIGO CTG system from 1987. The study aimed to determine time courses and sensitivity between the systems in classifying CTG + ST events to indicate metabolic acidosis at birth.Material and methods: Forty-four cases with umbilical cord artery metabolic acidosis were retrieved from a European multicenter database. CTG patterns and timing of the first occurring significant ST events were evaluated post hoc in consensus by an expert panel and sensitivity statistics were performed. Wilcoxon's matched-pairs signed-ranks test and McNemar's test were used with a two-tailed p < .05 regarded significant.Results: STAN2007 had a higher sensitivity (73 versus 43%, p = .0002) and alarmed for metabolic acidosis in mean 34 min earlier than the FIGO2015 system did (p = .002). In every fourth case, the time difference was ≥20 min.Conclusions: In this simulation study, surveillance with STAN2007 combined with fetal ECG ST analysis had a significantly higher sensitivity and would have alarmed for metabolic acidosis significantly earlier than the new FIGO system would have.

The importance of the learning process in ST analysis interpretation and its impact in improving clinical and neonatal outcomes

BACKGROUND

Intrapartum fetal heart rate monitoring was introduced with the goal to reduce fetal hypoxia and deaths. However, continuous fetal heart rate monitoring has been shown to have a high sensitivity but also a high false-positive rate. To improve specificity, adjunctive technologies have been developed to identify fetuses at risk for intrapartum asphyxia. Intensive research on the value of ST-segment analysis of the fetal electrocardiogram as an adjunct to standard electronic fetal monitoring in lowering the rates of fetal metabolic acidosis and operative deliveries has been ongoing. The conflicting results in randomized and observational studies may partly be due to differences in study design.

OBJECTIVE

This study aims to determine the significance of the learning process for the introduction of ST analysis into clinical practice and its impact on initial and subsequent obstetric outcomes.

STUDY DESIGN

This was a prospective observational study with the primary objective to evaluate the importance of the learning period on the rates of metabolic acidosis and operative deliveries after the implementation of ST analysis. The study was conducted at the Turku University Hospital, Turku, Finland, with 3400-4200 annual deliveries. The whole study population consisted of all 42,146 deliveries during the study period 2001 through 2011. The ST analysis usage rate was 18%. The data were collected prospectively from labors monitored with ST analysis as an adjunct to conventional intrapartum fetal heart rate monitoring. Primary endpoints were the rates of metabolic acidosis (cord artery pH <7.05 and an extracellular fluid compartment base deficit >12.0 mmol/L), fetal scalp blood sampling, and operative deliveries. Comparisons of these outcomes were made between the initiation period (the first 2 years) and the subsequent usage period (the next 9 years).

RESULTS

In the whole study population the prevalence of cord pH <7.05 decreased from 1.5-0.81% (relative risk, 0.54; 95% confidence interval, 0.43-0.67), the rate of cesarean deliveries from 17.2-14.1% (relative risk, 0.82; 95% confidence interval, 0.89-0.97), and the rate of fetal scalp blood sampling from 1.75-0.82% (relative risk, 0.47; 95% confidence interval, 0.38-0.58) when the 2 study periods were compared. In the ST analysis group, the frequency of cord metabolic acidosis rate was reduced from 1.0-0.25% (relative risk, 0.33; 95% confidence interval, 0.15-0.72).

CONCLUSION

We provide evidence that the results improve over time and there is a learning curve in the introduction of the ST analysis method. This was demonstrated by the lower rates of metabolic acidosis and operative deliveries after the initial implementation period.

Interobserver agreement in analysis of cardiotocograms recorded during trial of labor after cesarean

Introduction: To examine interobserver agreement in intrapartum cardiotocography (CTG) classification in women undergoing trial of labor after a cesarean section (TOLAC) at term with or without complete uterine rupture. Materials and methods: Nineteen blinded and independent Danish obstetricians assessed CTG tracings from 47 women (174 individual pages) with a complete uterine rupture during TOLAC and 37 women (133 individual pages) with no uterine rupture during TOLAC. Individual pages with CTG tracings lasting at least 20 min were evaluated by three different assessors and counted as an individual case. The tracings were analyzed according to the modified version of the Federation of Gynaecology and Obstetrics (FIGO) guidelines elaborated for the use of STAN (ST-analysis). Occurrence of defined abnormalities was recorded and the tracings were classified as normal, suspicious, pathological, or preterminal. The interobserver agreement was evaluated using Fleiss' kappa. Results: Agreement on classification of a preterminal CTG was almost perfect. The interobserver agreement on normal, suspicious or pathological CTG was moderate to substantial. Regarding the presence of severe variable decelerations, the agreement was moderate. No statistical difference was found in the interobserver agreement between classification of tracings from women undergoing TOLAC with and without complete uterine rupture. Conclusions: The interobserver agreement on classification of CTG tracings from high-risk deliveries during TOLAC is best for assessment of a preterminal CTG and the poorest for the identification of severe variable decelerations.

Risk of operative delivery for intrapartum fetal compromise in small-for-gestational-age fetuses at term: an internally validated prediction model

BACKGROUND

Small-for-gestational-age fetuses are at an increased risk of intrapartum fetal compromise requiring operative delivery. Factors associated with the risk of intrapartum fetal compromise are yet to be established, and a comprehensive model accounting for both the antenatal and intrapartum variables is lacking.

OBJECTIVE

We aimed to develop and validate a predictive model for the risk of operative delivery for presumed intrapartum fetal compromise in fetuses suspected to be small for gestational age at term.

STUDY DESIGN

This was a single-center cohort study of small-for-gestational-age fetuses, defined as estimated fetal weight below the 10th centile in singleton pregnancies at term. The variables included known risk factors for operative delivery because of fetal compromise: maternal characteristics, estimated fetal weight, abdominal circumference, Doppler parameters, gestational age at delivery, induction of labor, and intrapartum risk factors (presence of meconium, augmentation of labor using oxytocin, the use of epidural analgesia, intrapartum pyrexia, and hemorrhage). The receiver-operating characteristics curve analysis was used to investigate the predictive accuracy. Internal validation of the models was performed with bootstrapped data sets.

RESULTS

A total of 927 term pregnancies with 18.7% operative deliveries were included. The antenatal model (area under the curve, 0.69; 95% confidence interval, 0.65-0.73) using only the antenatal risk factors included parity, abdominal circumference centile, gestational age at delivery beyond 39 weeks' gestation, and the cerebroplacental ratio multiples of median. The combined model (area under the curve, 0.76; 95% confidence interval, 0.72-0.80), using both the antenatal and intrapartum risk factors, included the gestational age at delivery beyond 39 weeks' gestation (odds ratio, 1.62; 95% confidence interval, 1.14-2.56), the cerebroplacental ratio multiples of median (odds ratio, 0.38; 95% confidence interval, 0.18-0.79), parity (odds ratio 0.35; 95% confidence interval, 0.22-0.54), induction of labor (odds ratio 1.63; 95% confidence interval, 1.11-2.40), augmentation using oxytocin (odds ratio, 1.84; 95% confidence interval, 1.23-2.73) and the use of epidural analgesia (odds ratio, 2.80; 95% confidence interval, 1.94-4.04). The results indicate that the model has good discrimination and, according to the Hosmer-Lemeshow test, has good fit (P = .591).

CONCLUSION

The prediction model demonstrates 6 important risk factors that are associated with the risk of operative delivery for fetal compromise in small-for-gestational-age fetuses at term. The model shows good discrimination and fit and has the potential to be used for clinical decision making and to counsel women about their individual intrapartum risk.

Is cerebroplacental ratio a marker of impaired fetal growth velocity and adverse pregnancy outcome?

BACKGROUND

The cerebroplacental ratio has been proposed as a marker of failure to reach growth potential near term. Low cerebroplacental ratio, regardless of the fetal size, is independently associated with the need for operative delivery for presumed fetal compromise and with neonatal unit admission at term.

OBJECTIVE

The main aim of this study was to evaluate whether the cerebroplacental ratio at term is a marker of reduced fetal growth rate. The secondary aim was to investigate the relationship between a low cerebroplacental ratio at term, reduced fetal growth velocity, and adverse pregnancy outcome.

STUDY DESIGN

This was a retrospective cohort study of singleton pregnancies in a tertiary referral center. The abdominal circumference was measured at 20-24 weeks' gestation and both abdominal circumference and fetal Dopplers recorded at or beyond 35 weeks, within 2 weeks of delivery. Abdominal circumference and birthweight values were converted into Z scores and centiles, respectively, and fetal Doppler parameters into multiples of median, adjusting for gestational age. Abdominal circumference growth velocity was quantified using the difference in the abdominal circumference Z score, comparing the scan at or beyond 35 weeks with the scan at 20-24 weeks. Both univariable and multivariable logistic regression analyses were performed to investigate the association between low cerebroplacental ratio and the low abdominal circumference growth velocity (in the lowest decile) and to identify and adjust for potential confounders. As a sensitivity analysis, we refitted the model excluding the data on pregnancies with small-for-gestational-age neonates.

RESULTS

The study included 7944 pregnancies. Low cerebroplacental ratio multiples of median was significantly associated with both low abdominal circumference growth velocity (adjusted odds ratio, 2.10; 95% confidence interval, 1.71-2.57, P <0.001) and small for gestational age (adjusted odds ratio, 3.60; 95% confidence interval, 3.04-4.25, P < .001). After the exclusion of pregnancies resulting in small-for-gestational-age neonates, a low cerebroplacental ratio multiples of the median remained significantly associated with both low abdominal circumference growth velocity (adjusted odds ratio, 1.76; 95% confidence interval, 1.34-2.30, P < .001) and birthweight centile (adjusted odds ratio, 0.99; 95% confidence interval, 0.998-0.995, P < .001). The need for operative delivery for fetal compromise was significantly associated with a low cerebroplacental ratio (adjusted odds ratio, 1.40; 95% confidence interval, 1.10-1.78, P = .006), even after adjusting for both the umbilical artery pulsatility index multiples of the median and middle cerebral artery pulsatility index multiples of median. The results were similar, even after the exclusion of pregnancies resulting in small-for-gestational-age neonates (adjusted odds ratio, 1.39; 95% confidence interval, 1.06-1.84, P = .018). Low cerebroplacental ratio multiples of the median remained significantly associated with the risk of operative delivery for presumed fetal compromise (P < .001), even after adjusting for the known antenatal and intrapartum risk factors. These associations persisted, even after the exclusion of small-for-gestational-age births. In appropriate-for-gestational-age-sized fetuses, abdominal circumference growth velocity was significantly lower in those with a low cerebroplacental ratio multiples of the median than in those with normal cerebroplacental ratio multiples of the median (P < .001).

CONCLUSION

The cerebroplacental ratio is a marker of impaired fetal growth velocity and adverse pregnancy outcome, even in fetuses whose size is considered appropriate using conventional biometry.

Understanding fetal physiology and second line monitoring during labor

Cardiotocography (CTG) is a technique used to monitor intrapartum fetal condition and is one of the most common obstetric procedures. Second line methods of fetal monitoring have been developed in an attempt to reduce unnecessary interventions due to continuous cardiotocography and to better identify fetuses at risk of intrapartum asphyxia. The acid-base balance of the fetus is evaluated by fetal blood scalp samples, the modification of the myocardial oxygenation by the fetal ECG ST-segment analysis (STAN) and the autonomic nervous system by the power spectral analysis of the fetal heart variability. To correctly interpret the features observed on CTG traces or second line methods, it seems important to understand normal physiology during labor and the compensatory mechanisms of the fetus in case of hypoxemia. Therefore, the aim of this review is first to describe fetal physiology during labor and then to explain the modification of the second line monitoring during labor.

Cardiotocography in breech versus vertex delivery: an examiner-blinded, cross-sectional nested case-control study

Background

The safety of vaginal breech delivery has been debated for decades. Although it has been shown to predispose infants to immediate depression, several observational studies have also shown that attempting vaginal breech delivery does not increase perinatal morbidity or low Apgar score at the age of five minutes. Cardiotocography monitoring is recommended during vaginal breech delivery, but comparative data describing differences between cardiotocography tracings in breech and vertex deliveries is scarce. This study aims to evaluate differences in intrapartum cardiotocography tracings between breech and vertex deliveries in the final 60 min of delivery. A secondary goal is to identify risk factors for suboptimal neonatal outcome in the study population.

Methods

One hundred eight breech and 108 vertex singleton, intended vaginal deliveries at term from a tertiary hospital with 5000 annual deliveries were included. Two experienced obstetricians, blinded to fetal presentation, neonatal outcome and actual mode of delivery, evaluated traces recorded 60 min before delivery. They provided a three-tier classification and evaluated different trace features according to FIGO (1987) guidelines. Factors associated with acidemia and low Apgar scores were identified by univariate and multivariable analyses performed with binary logistic regression. Student’s T-test and chi-square test were used, as appropriate.

Results

Late decelerations were seen in 13.9 % of breech and 2.8 % of vertex deliveries (p = 0.003) and decreased variability in 26.9 % of breech and 8.3 % of vertex deliveries (p < 0.001). In multivariable analysis complicated variable decelerations and breech presentation were identified as risk factors for neonatal acidemia and low Apgar score at the age of five minutes. Pathological trace and breech presentation were independent risk factors for low Apgar score at the age of one minute.

Conclusions

Decreased variability and late decelerations were more prevalent in breech compared to vertex deliveries. Pathological trace predicts immediate neonatal depression and especially complicated variable decelerations may signal more severe distress. Further research is needed to create guidelines for safe management of vaginal breech delivery.

[Per partum acidosis: Interest and feasibility of cerebral Doppler during labor]

OBJECTIVES

To evaluate feasibility and interest of fetal cerebral Doppler during labor and the link with fetal pH to predict perinatal fetal asphyxia.

METHODS

Our prospective study in a university perinatal center, included patients during labor. There were no risk factors during pregnancy and patients were included after 37 weeks of pregnancy. For each patient an ultrasound with cerebral Doppler was done concomitant to a fetal scalp blood sample. We collected maternal and fetal characteristics as well as cervix dilatation, fetal heart rate analysis and fetal presentation.

RESULTS

Among 49 patients included over a period of 4 months, cerebral Doppler failed in 7 cases (11%). Majority of failure occurred at 10cm of dilatation (P=0.007, OR=14.1 [1.483; 709.1275]). Others factors like: maternal age, body mass index, parity, history of C-Section were not associated with higher rate of failure. We did not found either significant correlation between cerebral fetal Doppler and pH on fetal scalp blood sample (r=0.15) nor pH at cord blood sample (r=0.13). No threshold of cerebral Doppler is significant for fetal asphyxia prediction.

CONCLUSION

Fetal cerebral Doppler is feasible during labor with a low rate of failure but not a good exam to predict fetal acidosis and asphyxia.

Impact of maternal obesity on the fetal electrocardiogram during labor

OBJECTIVE

Maternal obesity affects one in every five women giving birth worldwide. This condition is associated with adverse perinatal outcomes, as well as increased morbidity and mortality for mother and offspring.

METHODS

We carried out a prospective study at the University of Pecs Medical Center, Pecs, Hungary, between 1 January 2013 and 1 January 2014. We enrolled 60 obese (body mass index >30 kg/m(2)) low-risk pregnant women and 108 age-, ethnicity-, and parity-matched nonobese pregnant control subjects. The ST segment of the fetal electrocardiogram was assessed by STAN® monitoring. Neonatal outcomes and cord gas analysis of the umbilical vessels were evaluated after birth.

RESULTS

No infant with definitive metabolic acidosis was delivered in either group. We observed 32 and 106 ST events in the obese and control group, respectively, but this difference was not statistically significant. To date, none of the infants delivered as part of this study have demonstrated developmental insufficiency.

CONCLUSIONS

Obesity might not influence the fetal electrocardiogram during labor as an independent risk factor for adverse pregnancy outcomes. Studies with larger cohort sizes are needed to confirm our findings.

Intrapartum electrocardiogram alteration in fetuses with congenital heart disease: a case-control study

OBJECTIVE

To assess if the fetal electrocardiogram especially ST segment is modified by congenital heart diseases: modifications in frequencies of the different ST events and modifications in signal quality.

STUDY DESIGN

A retrospective case-control study, comparing frequencies of the different ST events and the quality of the signal between fetuses with congenital heart diseases and fetuses without congenital heart disease. From 2000 to 2011, fifty-eight fetuses with congenital heart disease had their heart rate recording using a STAN device during labor. Control group was fetuses who were born just before a case and had a STAN as a second line for intrapartum surveillance. Cases and controls were matched on parity, gestational age at birth, presence of growth restriction and umbilical artery pH. Frequencies of the different ST event and quality of the signal were first analyzed for the global labor recording, and then separately for the first and the second phase of labor.

RESULTS

No statistically significant difference in ST event frequencies between fetuses with congenital heart disease and the control group was found. Regarding the quality of the signal, 11.49% (±18.82) of recording time is a signal loss for fetus with congenital heart disease whereas only 5.18% (±10.67) for the control group (p=0.028).

CONCLUSION

This is the first study investigating for intrapartum electrocardiogram modification in fetus with congenital heart disease. Congenital heart diseases do not modify frequencies of ST events.

Computer analysis of foetal monitoring signals

Five systems for computer analysis of foetal monitoring signals are currently available, incorporating the evaluation of cardiotocographic (CTG) or combined CTG with electrocardiographic ST data. All systems have been integrated with central monitoring stations, allowing the simultaneous monitoring of several tracings on the same computer screen in multiple hospital locations. Computer analysis elicits real-time visual and sound alerts for health care professionals when abnormal patterns are detected, with the aim of prompting a re-evaluation and subsequent clinical action, if considered necessary. Comparison between the CTG analyses provided by the computer and clinical experts has been carried out in all systems, and in three of them, the accuracy of computer alerts in predicting newborn outcomes was evaluated. Comparisons between these studies are hampered by the differences in selection criteria and outcomes. Two of these systems have just completed multicentre randomised clinical trials comparing them with conventional CTG monitoring, and their results are awaited shortly. For the time being, there is limited evidence regarding the impact of computer analysis of foetal monitoring signals on perinatal indicators and on health care professionals' behaviour.

Is fetal cerebroplacental ratio an independent predictor of intrapartum fetal compromise and neonatal unit admission?

OBJECTIVE

We sought to evaluate the association between fetal cerebroplacental ratio (CPR) and intrapartum fetal compromise and admission to the neonatal unit (NNU) in term pregnancies.

STUDY DESIGN

This was a retrospective cohort study in a single tertiary referral center over a 14-year period from 2000 through 2013. The umbilical artery pulsatility index, middle cerebral artery pulsatility index, and CPR were recorded within 2 weeks of delivery. The birthweight (BW) values were converted into centiles and Doppler parameters converted into multiples of median (MoM), adjusting for gestational age using reference ranges. Logistic regression analysis was performed to identify, and adjust for, potential confounders.

RESULTS

The study cohort included 9772 singleton pregnancies. The rates of operative delivery for presumed fetal compromise and neonatal admission were 17.2% and 3.9%, respectively. Doppler CPR MoM was significantly lower in pregnancies requiring operative delivery or admission to NNU for presumed fetal compromise (P < .01). On multivariate logistic regression, both CPR MoM and BW centile were independently associated with the risk of operative delivery for presumed fetal compromise (adjusted odds ratio [OR], 0.67; 95% confidence interval [CI], 0.52-0.87; P = .003 and adjusted OR, 0.994; 95% CI, 0.992-0.997; P < .001, respectively). The latter associations persisted even after exclusion of small-for-gestational-age cases from the cohort. Multivariate logistic regression also demonstrated that CPR MoM was an independent predictor for NNU admission at term (adjusted OR, 0.55; 95% CI, 0.33-0.92; P = .021), while BW centile was not (adjusted OR, 1.00; 95% CI, 0.99-1.00; P = .794). The rates of operative delivery for presumed fetal compromise were significantly higher for appropriate-for-gestational-age fetuses with low CPR MoM (22.3%) compared to small-for-gestational-age fetuses with normal CPR MoM (17.3%).

CONCLUSION

Lower fetal CPR, regardless of the fetal size, was independently associated with the need for operative delivery for presumed fetal compromise and with NNU admission at term. The extent to which fetal hemodynamic status could be used to predict perinatal morbidity and optimize the mode of delivery merits further investigation.

Feasibility of noninvasive fetal electrocardiographic monitoring in a clinical setting

Cardiac rhythm is an essential component of fetal cardiac evaluation. The Monica AN24 is a fetal heart rate monitor that may provide a quick, inexpensive modality for obtaining a noninvasive fetal electrocardiogram (fECG) in a clinical setting. The fECG device has the ability to acquire fECG signals and allow calculation of fetal cardiac time intervals between 16- and 42-week gestational age (GA). We aimed to demonstrate the feasibility of fECG acquisition in a busy fetal cardiology clinic using the Monica fetal heart rate monitor. This is a prospective observational pilot study of fECG acquired from fetuses referred for fetal echocardiography. Recordings were performed for 5-15 min. Maternal signals were attenuated and fECG averaged. fECG and fetal cardiac time intervals (PR, QRS, RR, and QT) were evaluated by two cardiologists independently and inter-observer reliability was assessed using intraclass coefficient (ICC). Sixty fECGs were collected from 50 mothers (mean GA 28.1 ± 6.1). Adequate signal-averaged waveforms were obtained in 20 studies with 259 cardiac cycles. Waveforms could not be obtained between 26 and 30 weeks. Fetal cardiac time intervals were measured and were reproducible for PR (ICC = 0.89; CI 0.77-0.94), QRS (ICC = 0.79; CI 0.51-0.91), and RR (ICC = 0.77; CI 0.53-0.88). QT ICC was poor due to suboptimal T-wave tracings. Acquisition of fECG and measurement of fetal cardiac time intervals is feasible in a clinical setting between 19- and 42-week GA, though tracings are difficult to obtain, especially between 26 and 30 weeks. There was high reliability in fetal cardiac time intervals measurements, except for QT. The device may be useful for assessing atrioventricular/intraventricular conduction in fetuses from 20 to 26 and >30 weeks. Techniques to improve signal acquisition, namely T-wave amplification, are ongoing.

Sympathetic neural activation does not mediate heart rate variability during repeated brief umbilical cord occlusions in near-term fetal sheep

Changes in fetal heart rate variability (FHRV) and ST segment elevation (measured as the T/QRS ratio) are used to evaluate fetal adaptation to labour. The sympathetic nervous system (SNS) is an important contributor to FHRV under healthy normoxic conditions, and is critical for rapid support of blood pressure during brief labour-like asphyxia. However, although it has been assumed that SNS activity contributes to FHRV during labour; this has never been tested, and it is unclear whether the SNS contributes to the rapid increase in T/QRS ratio during brief asphyxia. Thirteen chronically instrumented fetal sheep at 0.85 of gestation received either chemical sympathectomy with 6-hydroxydopamine (6-OHDA; n = 6) or sham treatment (control; n = 7), followed 4-5 days later by 2 min episodes of complete umbilical cord occlusion repeated every 5 min for up to 4 h, or until mean arterial blood pressure fell to <20 mmHg for two successive occlusions. FHRV was decreased before occlusions in the 6-OHDA group (P < 0.05) and 2-4.5 h during recovery after occlusions (P < 0.05) compared to the control group. During each occlusion there was a rapid increase in T/QRS ratio. Between successive occlusions the T/QRS ratio rapidly returned to baseline, and FHRV increased above baseline in both groups (P < 0.05), with no significant effect of sympathectomy on FHRV or T/QRS ratio. In conclusion, these data show that SNS activity does not mediate the increase in FHRV between repeated episodes of brief umbilical cord occlusion or the transient increase in T/QRS ratio during occlusions.

Maternal allopurinol administration during suspected fetal hypoxia: a novel neuroprotective intervention? A multicentre randomised placebo controlled trial

OBJECTIVE

To determine whether maternal allopurinol treatment during suspected fetal hypoxia would reduce the release of biomarkers associated with neonatal brain damage.

DESIGN

A randomised double-blind placebo controlled multicentre trial.

PATIENTS

We studied women in labour at term with clinical indices of fetal hypoxia, prompting immediate delivery.

SETTING

Delivery rooms of 11 Dutch hospitals.

INTERVENTION

When immediate delivery was foreseen based on suspected fetal hypoxia, women were allocated to receive allopurinol 500 mg intravenous (ALLO) or placebo intravenous (CONT).

MAIN OUTCOME MEASURES

Primary endpoint was the difference in cord S100ß, a tissue-specific biomarker for brain damage.

RESULTS

222 women were randomised to receive allopurinol (ALLO, n=111) or placebo (CONT, n=111). Cord S100ß was not significantly different between the two groups: 44.5 pg/mL (IQR 20.2-71.4) in the ALLO group versus 54.9 pg/mL (IQR 26.8-94.7) in the CONT group (difference in median -7.69 (95% CI -24.9 to 9.52)). Post hoc subgroup analysis showed a potential treatment effect of allopurinol on the proportion of infants with a cord S100ß value above the 75th percentile in girls (ALLO n=5 (12%) vs CONT n=10 (31%); risk ratio (RR) 0.37 (95% CI 0.14 to 0.99)) but not in boys (ALLO n=18 (32%) vs CONT n=15 (25%); RR 1.4 (95% CI 0.84 to 2.3)). Also, cord neuroketal levels were significantly lower in girls treated with allopurinol as compared with placebo treated girls: 18.0 pg/mL (95% CI 12.1 to 26.9) in the ALLO group versus 32.2 pg/mL (95% CI 22.7 to 45.7) in the CONT group (geometric mean difference -16.4 (95% CI -24.6 to -1.64)).

CONCLUSIONS

Maternal treatment with allopurinol during fetal hypoxia did not significantly lower neuronal damage markers in cord blood. Post hoc analysis revealed a potential beneficial treatment effect in girls.

TRIAL REGISTRATION NUMBER

NCT00189007, Dutch Trial Register NTR1383.

Expert review--identification of intra-partum fetal compromise

Whilst most cases of cerebral palsy occur as a consequence of an ante-natal insult, a significant proportion, particularly in the term fetus, are attributable to intra-partum hypoxia. Intra-partum monitoring using continuous fetal heart rate assessment has led to an increased incidence of operative delivery without a concurrent reduction in the incidence of cerebral palsy. Despite this, birth asphyxia remains the strongest and most consistent risk factor for cerebral palsy in term infants. This review evaluates current intra-partum monitoring techniques as well as alternative approaches aimed at better identification of the fetus at risk of compromise in labour.

The added predictive value of biphasic events in ST analysis of the fetal electrocardiogram for intrapartum fetal monitoring

OBJECTIVE

To study the predictive value of biphasic ST-events for interventions for suspected fetal distress and adverse neonatal outcome, when using ST-analysis of the fetal electrocardiogram (FECG) for intrapartum fetal monitoring.

DESIGN

Prospective cohort study.

SETTING

Three academic hospitals in Sweden.

POPULATION

Women in labor with a high-risk singleton fetus in cephalic position beyond 36 weeks of gestation.

METHODS

In women in labor who were monitored with conventional cardiotocography, ST-waveform analysis was recorded and concealed. Traces with biphasic ST-events of the FECG (index) were compared with traces without biphasic events of the FECG. The ability of biphasic events to predict interventions for suspected fetal distress and adverse outcome was assessed using univariable and multivariable logistic regression analyses.

MAIN OUTCOME MEASURES

Interventions for suspected fetal distress and adverse outcome (defined as presence of metabolic acidosis (i.e. umbilical cord pH <7.05 and base deficit in extracellular fluid >12 mmol), umbilical cord pH <7.00, 5-min Apgar score <7, admittance to neonatal intensive care unit or perinatal death).

RESULTS

Although the presence of biphasic events of the FECG was associated with more interventions for fetal distress and an increased risk of adverse outcome compared with cases with no biphasic events, the presence of significant (i.e. intervention advised according to cardiotocography interpretation) biphasic events showed no independent association with interventions for fetal distress [odds ratio (OR) 1.71, 95% confidence interval (CI) 0.65-4.50] or adverse outcome (OR 1.96, 95% CI 0.74-5.24).

CONCLUSION

The presence of significant biphasic events did not discriminate in the prediction of interventions for fetal distress or adverse outcome. Therefore, biphasic events in relation to ST-analysis monitoring during birth should be omitted if future studies confirm our findings.

A critical appraisal of the evidence for using cardiotocography plus ECG ST interval analysis for fetal surveillance in labor. Part II: the meta-analyses

We appraised the methodology, execution and quality of the five published meta-analyses that are based on the five randomized controlled trials which compared cardiotocography (CTG)+ST analysis to cardiotocography. The meta-analyses contained errors, either created de novo in handling of original data or from a failure to recognize essential differences among the randomized controlled trials, particularly in their inclusion criteria and outcome parameters. No meta-analysis contained complete and relevant data from all five randomized controlled trials. We believe that one randomized controlled trial excluded in two of the meta-analyses should have been included, whereas one randomized controlled trial that was included in all meta-analyses, should have been excluded. After correction of the uncovered errors and exclusion of the randomized controlled trial that we deemed inappropriate, our new meta-analysis showed that CTG+ST monitoring significantly reduces the fetal scalp blood sampling usage (risk ratio 0.64; 95% confidence interval 0.47-0.88), total operative delivery rate (0.93; 0.88-0.99) and metabolic acidosis rate (0.61; 0.41-0.91).

Impact of fetal pulse oximetry and ST analysis surveillance withdrawal on rates of obstetric surgery and frequency of low birth umbilical artery pH: a cause of rising caesarean rates?

A retrospective observational study on a sample of 13,413 deliveries analysed the effect of a withdrawal of the CTG additional diagnostic methods of fetal hypoxia (fetal pulse oximetry and ST analysis of the fetal ECG) on operative delivery rates and frequency of the umbilical arterial pH < 7.15. Following the withdrawal, obstetricians are more likely to perform caesarean sections for fetal hypoxia (OR 2.23, 95% CI 1.94-2.55, p < 0.0001) and labour dystocia (OR 1.45, 95% CI 1.18-1.77, p = 0.0003), which increases the overall caesarean rate (OR 1.49, 95% CI 1.38-1.61, p < 0.0001), although decreases the incidence of birth umbilical arterial pH < 7.15 (OR 0.43, 95% CI 0.22-0.85, p = 0.015). This also leads to the significant decline in overall frequency of instrumental vaginal deliveries (OR 0.58, 95% CI 0.48-0.71). In order to decrease the overall caesarean rate, obstetricians need to be supported by more accurate and possibly automated diagnostic tools for intrapartum fetal hypoxia.

Scientific and clinical evidence for the use of fetal ECG ST segment analysis (STAN)

Fetal electrocardiogram waveform analysis has been studied for many decades, but it is only in the last 20 years that computerization has made real-time analysis practical for clinical use. Changes in the ST segment have been shown to correlate with fetal condition, in particular with acid-base status. Meta-analysis of randomized trials (five in total, four using the computerized system) has shown that use of computerized ST segment analysis (STAN) reduces the need for fetal blood sampling by about 40%. However, although there are trends to lower rates of low Apgar scores and acidosis, the differences are not statistically significant. There is no effect on cesarean section rates. Disadvantages include the need for amniotic membranes to be ruptured so that a fetal scalp electrode can be applied, and the need for STAN values to be interpreted in conjunction with detailed fetal heart rate pattern analysis.

[Severe neonatal acidosis: comparison and analysis of obstetrical practices in two French perinatal centers]

OBJECTIVES

To identify and compare risk factors for severe neonatal acidosis, defined by an umbilical artery pH inferior to 7.00, and clinical practices in two different perinatal centers.

PATIENTS AND METHODS

In a retrospective study, from 2003 to 2008, in two university perinatal centers (Poitiers and Saint-Antoine in Paris) on all term pregnancies complicated by severe neonatal acidosis (umbilical artery pH<7.00), we elected to compare the following risk factors: maternal characteristics, medical and obstetrical histories, progress of pregnancy, labour and delivery as well as the neonatal status.

RESULTS

Among 23,508 births, 177 term newborns had severe neonatal acidosis. The rate was similar for both perinatal centers of Poitiers and Saint-Antoine (0.92% and 0.77% respectively). Factors associated with severe neonatal acidosis were similar in both centers: maternal age, thick meconium, prior cesarean section. There were differences in obstetrical practices between the two centers: there were more caesarean sections and assisted vaginal deliveries in Paris and more inductions of labour in Poitiers.

CONCLUSION

Severe neonatal acidosis is associated with the geographical origin, the progress of labour and the mode of delivery. It seems that severe neonatal acidosis is unrelated to cesarean delivery.