Intrapartum electronic fetal heart rate monitoring and the identification of metabolic acidosis and hypoxic-ischemic encephalopathy

A systematic catalog of studies on fetal heart rate pattern and neonatal outcome variables

OBJECTIVES

To study the methodology and results of studies assessing the relationship between fetal heart rate and specified neonatal outcomes including, heart rate, infection, necrotizing enterocolitis, intraventricular hemorrhage, hypoxic-ischemic encephalopathy, and seizure.

METHODS

Embase, Medline ALL, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, and CINAHL were searched from inception to October 5, 2023.

RESULTS

Forty-two studies were included, encompassing 57,232 cases that underwent fetal monitoring and were evaluated for neonatal outcome. Heterogeneity was observed in the timing and duration of fetal heart rate assessment, classification guidelines used, number of assessors, and definition and timing of neonatal outcome assessment. Nonreassuring fetal heart rate was linked to lower neonatal heart rate variability. A significant increase in abnormal fetal heart rate patterns were reported in neonates with hypoxic-ischemic encephalopathy, but the predictive ability was found to be limited. Conflicting results were reported regarding sepsis, seizure and intraventricular hemorrhage. No association was found between necrotizing enterocolitis rate and fetal heart rate.

CONCLUSIONS

There is great heterogeneity in the methodology used in studies evaluating the association between fetal heart rate and aforementioned neonatal outcomes. Hypoxic-ischemic encephalopathy was associated with increased abnormal fetal heart rate patterns, although the predictive ability was low. Further research on developing and evaluating an automated early warning system that integrates computerized cardiotocography with a perinatal health parameter database to provide objective alerts for patients at-risk is recommended.

Multi-organ dysfunction in infants with acidosis at birth in the absence of moderate to severe hypoxic ischemic encephalopathy

INTRODUCTION

Infants with perinatal asphyxia are at risk for organ failure aside from the brain, regardless of the severity of the asphyxial insult. We aimed to evaluate the presence of organ dysfunction other than the brain in newborns with moderate to severe acidosis at birth, in the absence of moderate to severe hypoxic ischemic encephalopathy.

MATERIALS AND METHODS

Data of 2 years were retrospectively recorded. Late preterm and term infants admitted to the intensive care unit with ph < 7.10 and BE < -12 mmol/l in the first hour were included in the absence of moderate to severe hypoxic ischemic encephalopathy. Respiratory dysfunction, hepatic dysfunction, renal dysfunction, myocardial depression, gastrointestinal problems, hematologic system dysfunction, and circulatory failure were evaluated.

RESULTS

Sixty-five infants were included [39 (37-40) weeks, 3040 (2655-3380) grams]. Fifty-six (86 %) infants had one or more dysfunction in any system [respiratory: 76.9 %, hepatic: 20.0 %, coagulation: 18.5 %, renal: 9.2 %, hematologic: 7.7 %, gastrointestinal: 3.0 %, and cardiac: 3.0 %]. Twenty infants had at least two affected systems. The incidence of coagulation dysfunctions was higher in the infants with severe acidosis (n = 25, ph < 7.00) than the infants with moderate acidosis (n = 40: pH = 7.00-7.10); 32 % vs 10 %; p = 0.03.

CONCLUSIONS

Moderate to severe fetal acidosis is associated with the development of extra-cranial organ dysfunctions in infants who do not require therapeutic hypothermia. A monitoring protocol is needed for infants with mild asphyxia in order to identify and manage potential complications. Coagulation system should be carefully evaluated.

The association of fetal acidemia with adverse neonatal outcomes at time of scheduled cesarean delivery

BACKGROUND

Fetal acidemia at the time of a scheduled cesarean delivery is generally unexpected. In the setting of reassuring preoperative monitoring, the duration of fetal acidemia in this scenario is presumably brief. The neonatal sequelae and risks associated with brief fetal acidemia in this setting are unknown.

OBJECTIVE

We aimed to assess whether fetal acidemia at the time of a scheduled prelabor cesarean delivery is associated with adverse neonatal outcomes.

STUDY DESIGN

This was a retrospective cohort study of singleton, term, nonanomalous, liveborn neonates delivered by scheduled cesarean delivery that was performed under regional anesthesia from 2004 to 2014 at a single tertiary care center with a universal umbilical cord gas policy. Neonates born to laboring gravidas and those whose cesarean delivery was performed for nonreassuring fetal status were excluded. All included patients had reassuring preoperative fetal monitoring. The primary outcome was a composite adverse neonatal outcome that included neonatal death, encephalopathy, therapeutic hypothermia, seizures, intubation, and respiratory distress. This outcome was compared between patients with and those without fetal acidemia (umbilical artery pH <7.2). A multivariable logistic regression was used to adjust for confounders. Cases of fetal acidemia were further characterized as respiratory, metabolic, or mixed acidemia based on additional umbilical cord gas values. Secondary analyses examining the association between the type of acidemia and neonatal outcomes were also performed.

RESULTS

Of 2081 neonates delivered via scheduled cesarean delivery, 252 (12.1%) had fetal acidemia at the time of delivery. Acidemia was more common in breech neonates and in neonates born to gravidas with obesity and gestational diabetes mellitus. Compared with fetuses with normal umbilical artery pH, those with fetal acidemia were at a significantly increased risk for adverse neonatal outcome (adjusted relative risk, 2.95; 95% confidence interval, 2.03-4.12). This increased risk was similar regardless of the type of acidemia.

CONCLUSION

Even a brief period of mild acidemia is associated with adverse neonatal outcomes at the time of a scheduled cesarean delivery despite reassuring preoperative monitoring. Addressing modifiable intraoperative factors that may contribute to fetal acidemia at the time of a scheduled cesarean delivery, such as maternal hypotension and prolonged operative time, is an important priority to potentially decrease neonatal morbidity in full-term gestations.

Mild Neonatal Acidemia is Associated with Neonatal Morbidity at Term

OBJECTIVE

The aim of this study is to determine the association between mild acidemia (umbilical artery [UA] pH: 7.11-7.19) and neonatal morbidity in neonates at term.

STUDY DESIGN

This is a secondary analysis of a prospective cohort of women admitted for labor at ≥37 weeks of gestation within a single institution from 2010 to 2015. Universal umbilical cord blood gas assessment was performed and validated. A composite neonatal morbidity index was created including respiratory distress, mechanical ventilation, meconium aspiration syndrome, suspected or confirmed sepsis, hypoxic-ischemic encephalopathy, need for therapeutic hypothermia, seizures and death. The cohort was stratified by UA pH into normal (≥7.20), mild acidemia (7.11-7.19), acidemia (7.00-7.10), and severe acidemia (≤7.00). A subanalysis was also performed where neonates with UA pH between 7.11 and 7.19 were further stratified into two groups (7.11-7.14 and 7.15-7.19) to determine if mildly acidotic infants at the lower end of the pH range were at increased risk of morbidity. Multivariable logistic regression was used to estimate the association between UA pH and neonatal morbidity.

RESULTS

Among 6,341 participants, 614 (9.7%) had mild acidemia. These infants were more likely to experience morbidity compared with those with normal UA pH (adjusted odds ratio [aOR]: 2.14; [1.68-2.73]). Among neonates with mild acidemia, UA pH 7.11 to 7.14 was associated with increased risk of composite neonatal morbidity (aOR: 3.02; [1.89-4.82]), as well as respiratory distress and suspected or confirmed sepsis when compared with UA pH 7.15 to 7.19.

CONCLUSION

These data demonstrate that term neonates with mild acidemia at birth are at higher odds for short-term morbidity compared with neonates with normal UA pH. Furthermore, among neonates with mild acidemia, those with lower UA pH had worse neonatal outcomes than those with higher UA pH. This suggests that closer evaluation of neonates with UA pH higher than traditionally used could allow for earlier detection of morbidity and possible intervention.

KEY POINTS

· Neonates with mild acidemia (umbilical artery [UA] pH: 7.11-7.19) demonstrated an increased risk of composite morbidity compared with those with normal UA pH (≥7.20).. · Among neonates with mild acidemia, those with lower UA pH (7.11-7.14) had a greater risk of morbidity compared with those with higher UA pH (7.15-7.19), suggesting a progression of risk of morbidity as UA pH decreases.. · The majority of prior research has focused on severe acidemia (UA pH ≤ 7.00) using outcomes of severe neurologic morbidity and mortality. These data suggest that an increased risk of morbidity exists at higher pH values when more proximal and less severe outcomes are included, such as respiratory distress and neonatal sepsis..

Markers of perinatal hypoxia-ischaemia and neurological injury: assessing the impact of insult duration

Hypoxic-ischaemic insults occurring during or after birth can cause both acute and long-term neurological impairment. The duration of the insult is a critical factor, but most published reports of duration have important limitations. After the onset of a persistent bradycardia in 125 term born infants, abnormal outcomes occurred in two by 10 minutes, in 12 out of 47 (26%) delivered between 11 and 20 minutes, and in 55 out of 65 (85%) delivered after 20 minutes. Series with unspecified gestation or including infants born preterm give comparable results in over 500 additional cases. Before 20 minutes there was little correlation with severity, while after 20 minutes most were severely impaired. Limited neuroimaging data suggest that damage restricted to the basal ganglia and thalamus may begin to occur after 10 minutes, associated Rolandic damage after 15 minutes, and other cortical involvement after 20 minutes. Associated white matter damage can occur after any duration. There were little data for other patterns of damage. WHAT THIS PAPER ADDS: Some term born infants can withstand 20 minutes of fetal bradycardia without acute or chronic damage. Durations in humans are not the same as in animal models.

Clinician Identification of Birth Asphyxia Using Intrapartum Cardiotocography Among Neonates With and Without Encephalopathy in New Zealand

IMPORTANCE

Despite improvements in antenatal care and increasing cesarean delivery rates, birth asphyxia leading to neonatal encephalopathy (NE) continues to contribute to neonatal death and long-term neurodevelopmental disability. Cardiotocography (CTG) has been used in labor for several decades to detect a stressed fetus so that delivery can be expedited and NE avoided.

OBJECTIVE

To investigate whether experienced clinicians can detect and respond to abnormal readings from CTGs during the penultimate hour before birth in infants with moderate to severe NE but no acute peripartum event.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study included 10 practicing obstetricians and midwives at maternity hospitals in New Zealand. Participants, who were masked to the perinatal outcome, were asked to assess CTG tracings from 35 neonates with NE and evidence of birth hypoxia (ie, cases) and 105 neonates without NE or birth hypoxia (ie, controls), all of whom were born in 2010 to 2011. Data analysis was conducted from May to December 2017.

EXPOSURES

Brief clinical details and 1 hour of CTG tracings from the penultimate hour before birth were provided for each baby. Clinicians assessed the CTG tracings and recommended a plan.

MAIN OUTCOMES AND MEASURES

Intra-assessor and interassessor agreement on CTG findings and action plans as well as sensitivity (ie, detection of NE) and specificity (ie, ruling out those without NE) for the assessment of abnormal CTG readings leading to immediate action (ie, fetal blood sample or immediate delivery) were reported.

RESULTS

A total of 35 infants (mean [SD] gestational age, 40 [1.4] weeks; 16 [45.7%] cesarean deliveries) were designated cases, and 105 infants (mean [SD] gestational age, 39.4 [1.2] weeks; 22 [21.0%] cesarean deliveries) were designated controls. No infants had congenital anomalies. The mean (range) sensitivity for detection of abnormal CTG results and for recommending immediate action for all assessors was 75% (63%-91%) and 41% (23%-57%), respectively, with a mean (range) specificity of 67% (53%-77%) and 87% (65%-99%), respectively. A sensitivity analysis including only assessors with 80% or more interassessor agreement only differed from the main analysis by 6% or less (mean [range] sensitivity for detection, 76% [63%-91%]; sensitivity for action plan, 36% [25%-49%]; specificity for detection, 71% [53%-77%]; and specificity for action plan, 93% [88%-99%]).

CONCLUSIONS AND RELEVANCE

Experienced clinicians detected 3 of 4 infants who were subsequently diagnosed with NE. Action to expedite delivery was recommended for more than 40% of infants with NE. These results indicate that CTG does not identify all infants at risk of NE, and that there is a need for further investment in new approaches to fetal surveillance in labor.

Threshold of metabolic acidosis associated with newborn cerebral palsy: medical legal implications

Obstetricians and gynecologists belong to 1 of the medical specialties with the highest rate of litigation claims. Among birth injury cases, those cases with cerebral palsy outcomes account for litigation settlements or judgments often in the millions of dollars. In cases of potential perinatal asphyxia, a threshold level of metabolic acidosis (base deficit ≥12 mmol/L) is necessary to attribute neonatal encephalopathy to an intrapartum hypoxic event. With increasing duration or severity of a hypoxic stress resulting in metabolic acidosis, newborn infant umbilical artery base deficit increases. It may be alleged that, as base deficit levels increase beyond 12 mmol/L, there is an increased likelihood and severity of cerebral palsy. As a corollary, it may be claimed that an earlier delivery (by minutes) would reduce the base deficit and prevent or reduce the severity of cerebral palsy. This issue is of relevance to obstetricians as defendants, because retrospective "expert" analysis of cases may suggest that optimal management decisions would have resulted in an earlier delivery. In addressing the association of metabolic acidosis and cerebral palsy, base deficit should be measured as the extracellular component (base deficit_{extracellular fluid}) rather than the commonly used base deficit_blood. Studies suggest that, beyond the base deficit threshold of 12 mmol/L, the incidence and severity of cerebral palsy does not significantly increase (until ≥20 mmol/L), although the risk of neonatal death rises markedly. Thus, among most infants with hypoxia-associated neonatal encephalopathy, the occurrence of cerebral palsy is unlikely to be impacted by delivery time variation of few minutes, and this argument should not serve as the basis for medical legal claims.

Elevated umbilical cord arterial lactate at birth and electronic fetal monitoring characteristics on admission and in the active phase

OBJECTIVE

To investigate the association between elevated umbilical arterial lactate at birth and electronic fetal monitoring (EFM) characteristics at admission and in the beginning of the active phase of labor.

STUDY DESIGN

Nested case-control study within a prospective cohort of laboring patients at term who achieved active labor. Neonates with umbilical arterial lactate ≥ 4 mmol/L (cases, n = 119), were matched 1:1 to controls with lactate < 4 mmol/L. EFM patterns were compared with multivariable logistic regression.

RESULT

There were no differences in EFM parameters in the first 60 minutes after admission. At the beginning of active labor, 13.5% of cases and 26.1% of controls had always category I tracings, adjusted odds ratio 0.48, 95% confidence interval 0.24-0.94). Cases were less likely to have an always category I tracing from admission into the active phase.

CONCLUSION

Elevated umbilical arterial lactate at birth is associated with distinct EFM patterns early in the labor course.

[Study of fetal heart rate abnormalities observed on cardiotocography in Lubumbashi: about a cases followed at the Lubumbashi University Clinic and the General Hospital of the Cinquantenaire]

Cardiotocography (CTG) has recently come into use in Lubumbashi but no thorough study has yet been conducted to identify its impact on perinatal morbi-mortality. This study aims to determine the frequency of fetal heart rate abnormalities (FHR)in order to identify the associated factors and to propose a suitable management. We conducted a cross-sectional, descriptive study of 411 women in labour over a period of 19 months (March 2015-December 2016). In patients with pathologic FHR abnormalities, sensitivity and positive predictive value of cardiotocography in the screening test for acute fetal distress were 82.95% and 45.35% respectively. FHR abnormalities were found in two women in labour out of five. Decelerations were the most frequent FHR abnormalities observed (50.8%) with a remarkable predominance of late decelerations (22.1% of all abnormalities). The factors associated with pathological FHR abnormalities were prolonged labor (OR = 14.64, CI = 3.91-54.81), chorioamnionitis (OR = 14.56, CI = 3.83-55.34), chronic maternal anemia (OR = 4.99, CI = 1.48-16.85), primiparity (OR = 2.69, CI = 1.49-4.85), prematurity (OR = 2.90, CI = 1.51-5.54) and prolonged pregnancy (OR = 3.22, CI = 1.38-7.52). Intrauterine growth retardation and arterial hypertension were mainly associated with flat lines and late decelerations (OR = 7.79, CI = 2.50-24.30 and OR=2.74, CI = 1.31-5.72). CTG is a screening tool for the identification of acute fetal distress but with high false-positive rate (55%); it should be associated with other second-line screening tests for acute fetal distress in order to reduce this rate. Factors associated with pathologic FHR abnormalities often cause acute fetal distress thus requiring a rigorous analysis of CTG traces.

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.

Comparison of ECG-based physiological markers for hypoxia in a preterm ovine model

BACKGROUND

Current methods for assessing perinatal hypoxic conditions did not improve infant outcomes. Various waveform-based and interval-based ECG markers have been suggested, but not directly compared. We compare performance of ECG markers in a standardized ovine model for fetal hypoxia.

METHODS

Sixty-nine fetal sheep of 0.7 gestation had ECG recorded 4 h before, during, and 4 h after a 25-min period of umbilical cord occlusion (UCO), leading to severe hypoxia. Various ECG markers were calculated, among which were heart rate (HR), HR-corrected ventricular depolarization/repolarization interval (QTc), and ST-segment analysis (STAN) episodic and baseline rise markers, analogue to clinical STAN device alarms. Performance of interval- and waveform-based ECG markers was assessed by correlating predicted and actual hypoxic/normoxic state.

RESULTS

Of the markers studied, HR and QTc demonstrated high sensitivity (≥86%), specificity (≥96%), and positive predictive value (PPV) (≥86%) and detected hypoxia in ≥90% of fetuses at 4 min after UCO. In contrast, STAN episodic and baseline rise markers displayed low sensitivity (≤20%) and could not detect severe fetal hypoxia in 65 and 28% of the animals, respectively.

CONCLUSION

Interval-based HR and QTc markers could assess the presence of severe hypoxia. Waveform-based STAN episodic and baseline rise markers were ineffective as markers for hypoxia.

Fetal heart rate monitoring: from Doppler to computerized analysis

The monitoring of fetal heart rate (FHR) status is an important method to check well-being of the baby during labor. Since the electronic FHR monitoring was introduced 40 years ago, it has been expected to be an innovative screening test to detect fetuses who are becoming hypoxic and who may benefit from cesarean delivery or operative vaginal delivery. However, several randomized controlled trials have failed to prove that electronic FHR monitoring had any benefit of reducing the perinatal mortality and morbidity. Also it is now clear that the FHR monitoring had high intra- and interobserver disagreements and increased the rate of cesarean delivery. Despite such limitations, the FHR monitoring is still one of the most important obstetric procedures in clinical practice, and the cardiotocogram is the most-used equipment. To supplement cardiotocogram, new methods of computerized FHR analysis and electrocardiogram have been developed, and several clinical researches have been currently performed. Computerized equipment makes us to analyze beat-to-beat variability and short term heart rate patterns. Furthermore, researches about multiparameters of FHR variability will be ongoing.

Fractal Analysis and Hurst Parameter for Intrapartum Fetal Heart Rate Variability Analysis: A Versatile Alternative to Frequency Bands and LF/HF Ratio

Background

The fetal heart rate (FHR) is commonly monitored during labor to detect early fetal acidosis. FHR variability is traditionally investigated using Fourier transform, often with adult predefined frequency band powers and the corresponding LF/HF ratio. However, fetal conditions differ from adults and modify spectrum repartition along frequencies.

Aims

This study questions the arbitrariness definition and relevance of the frequency band splitting procedure, and thus of the calculation of the underlying LF/HF ratio, as efficient tools for characterizing intrapartum FHR variability.

Study Design

The last 30 minutes before delivery of the intrapartum FHR were analyzed.

Subjects

Case-control study. A total of 45 singletons divided into two groups based on umbilical cord arterial pH: the Index group with pH ≤ 7.05 (n = 15) and Control group with pH > 7.05 (n = 30).

Outcome Measures

Frequency band-based LF/HF ratio and Hurst parameter.

Results

This study shows that the intrapartum FHR is characterized by fractal temporal dynamics and promotes the Hurst parameter as a potential marker of fetal acidosis. This parameter preserves the intuition of a power frequency balance, while avoiding the frequency band splitting procedure and thus the arbitrary choice of a frequency separating bands. The study also shows that extending the frequency range covered by the adult-based bands to higher and lower frequencies permits the Hurst parameter to achieve better performance for identifying fetal acidosis.

Conclusions

The Hurst parameter provides a robust and versatile tool for quantifying FHR variability, yields better acidosis detection performance compared to the LF/HF ratio, and avoids arbitrariness in spectral band splitting and definitions.

Neonatal encephalopathy and the association to asphyxia in labor

OBJECTIVE

In cases with moderate and severe neonatal encephalopathy, we aimed to determine the proportion that was attributable to asphyxia during labor and to investigate the association between cardiotocographic (CTG) patterns and neonatal outcome.

STUDY DESIGN

In a study population of 71,189 births from 2 Swedish university hospitals, 80 cases of neonatal encephalopathy were identified. Cases were categorized by admission CTG patterns (normal or abnormal) and by the presence of asphyxia (cord pH, <7.00; base deficit, ≥12 mmol/L). Cases with normal admission CTG patterns and asphyxia at birth were considered to experience asphyxia related to labor. CTG patterns were assessed for the 2 hours preceding delivery.

RESULTS

Admission CTG patterns were normal in 51 cases (64%) and abnormal in 29 cases (36%). The rate of cases attributable to asphyxia (ie, hypoxic ischemic encephalopathy) was 48 of 80 cases (60%), most of which evolved during labor (43/80 cases; 54%). Both severe neonatal encephalopathy and neonatal death were more frequent with an abnormal, rather than with a normal, admission CTG pattern (13 [45%] vs 11 [22%]; P = .03), and 6 [21%] vs 3 [6%]; P = .04), respectively. Comparison of cases with an abnormal and a normal admission CTG pattern also revealed more frequently observed decreased variability (12 [60%] and 8 [22%], respectively) and more late decelerations (8 [40%] and 1 [3%], respectively).

CONCLUSION

Moderate and severe encephalopathy is attributable to asphyxia in 60% of cases, most of which evolve during labor. An abnormal admission CTG pattern indicates a poorer neonatal outcome and more often is associated with pathologic CTG patterns preceding delivery.

Safe prevention of the primary cesarean delivery

In 2011, 1 in 3 women who gave birth in the United States did so by cesarean delivery. Cesarean birth can be lifesaving for the fetus, the mother, or both in certain cases. However, the rapid increase in cesarean birth rates from 1996 through 2011 without clear evidence of concomitant decreases in maternal or neonatal morbidity or mortality raises significant concern that cesarean delivery is overused. Variation in the rates of nulliparous, term, singleton, vertex cesarean births also indicates that clinical practice patterns affect the number of cesarean births performed. The most common indications for primary cesarean delivery include, in order of frequency, labor dystocia, abnormal or indeterminate (formerly, nonreassuring) fetal heart rate tracing, fetal malpresentation, multiple gestation, and suspected fetal macrosomia. Safe reduction of the rate of primary cesarean deliveries will require different approaches for each of these, as well as other, indications. For example, it may be necessary to revisit the definition of labor dystocia because recent data show that contemporary labor progresses at a rate substantially slower than what was historically taught. Additionally, improved and standardized fetal heart rate interpretation and management may have an effect. Increasing women's access to nonmedical interventions during labor, such as continuous labor and delivery support, also has been shown to reduce cesarean birth rates. External cephalic version for breech presentation and a trial of labor for women with twin gestations when the first twin is in cephalic presentation are other of several examples of interventions that can contribute to the safe lowering of the primary cesarean delivery rate.

Short term outcome of term newborns with unexpected umbilical cord arterial pH between 7.000 and 7.100

BACKGROUND

The relationship between cord arterial pH (CA-pH) > 7.000 and the neonatal outcome is not clear.

AIMS

To evaluate if asymptomatic infants born with unexpected cord arterial pH (CA-pH) between 7.000 and 7.100 develop clinical, biochemical, and instrumental signs of hypoxic cerebral, renal, and heart failure more frequently than symptomatic infants.

STUDY DESIGN

Term infants with CA-pH of 7.000-7.100 and appropriate birth weight were prospectively and consecutively enrolled and classified as asymptomatic, when they had no resuscitation, early respiratory distress or early abnormal neurologic signs, and symptomatic infants. Clinical, biochemical, and instrumental signs of hypoxic cerebral, renal, and heart failure were evaluated in the two groups.

RESULTS

A total of 53 infants were enrolled. Twenty-eight (53%) were asymptomatic. CA-pH was similar in both the groups, while the cTnI serum concentration in the first day of life and the occurrence of poor feeding were higher in the symptomatic than in asymptomatic infants. An arterial lactate level of ≥ 4.1 mmol/l measured in the first hour of life was an independent risk factor for the development of a symptomatic course.

CONCLUSIONS

In our population the majority of infants born with a CA-pH between 7.000 and 7.100 were asymptomatic and would not have needed immediate admission to the neonatal care unit. Symptomatic infants showed a higher occurrence of subclinical heart injury and poor feeding.

Electronic fetal monitoring in the United States: temporal trends and adverse perinatal outcomes

OBJECTIVE

To examine trends in electronic fetal monitoring (EFM) use and quantify the extent to which such trends are associated with changes in rates of primary cesarean delivery and neonatal morbidity and mortality.

METHODS

We carried out a retrospective study of more than 55 million nonanomalous singleton live births (24-44 weeks of gestation) delivered in the United States between 1990 and 2004. Changes in the risks of neonatal mortality, cesarean delivery, and operative vaginal delivery for fetal distress, 5-minute Apgar score lower than 4, and neonatal seizures (at 34 weeks of gestation or after) were examined in relation to changes in EFM use.

RESULTS

Electronic fetal monitoring use increased from 73.4% in 1990 to 85.7% in 2004, a relative increase of 17% (95% confidence interval 16-18%). This increase was associated with an additional 5% and 2% decline in early and late neonatal deaths, respectively, at 24-33 weeks of gestation as well as a 4-7% additional decline in the 5-minute Apgar score lower than 4 at 24-33, 34-36, and 37-44 weeks of gestation. Increasing EFM use was associated with a 2-4% incremental increased rate of both cesarean delivery and operative vaginal delivery for fetal distress at 24-33, 34-36, and 37-44 weeks of gestation. Increasing EFM was not associated with any temporal changes in the rate of neonatal seizures.

CONCLUSIONS

The temporal increase in EFM use in the United States appears to be modestly associated with the recent declines in neonatal mortality, especially at preterm gestations.

LEVEL OF EVIDENCE

II.

Why the term neonatal encephalopathy should be preferred over neonatal hypoxic-ischemic encephalopathy

The unresponsiveness of the full-term newborn is sometimes attributed to asphyxia, even when no severe physiologic disturbance occurred during labor and delivery. The controversy about whether to use the name "hypoxic-ischemic encephalopathy" or "newborn encephalopathy" has recently flared in publications directed toward pediatricians and neurologists. In this clinic opinion piece, I discuss the importance to obstetricians of this decision and explain why "newborn encephalopathy" should be the default term.

Comparison of midwife-led and consultant-led care of healthy women at low risk of childbirth complications in the Republic of Ireland: a randomised trial

BACKGROUND

No midwifery-led units existed in Ireland before 2004. The aim of this study was to compare midwife-led (MLU) versus consultant-led (CLU) care for healthy, pregnant women without risk factors for labour and delivery.

METHODS

An unblinded, pragmatic randomised trial was designed, funded by the Health Service Executive (Dublin North-East). Following ethical approval, all women booking prior to 24 weeks of pregnancy at two maternity hospitals with 1,300-3,200 births annually in Ireland were assessed for trial eligibility.1,653 consenting women were centrally randomised on a 2:1 ratio to MLU or CLU care, (1101:552). 'Intention-to-treat' analysis was used to compare 9 key neonatal and maternal outcomes.

RESULTS

No statistically significant difference was found between MLU and CLU in the seven key outcomes: caesarean birth (163 [14.8%] vs 84 [15.2%]; relative risk (RR) 0.97 [95% CI 0.76 to 1.24]), induction (248 [22.5%] vs 138 [25.0%]; RR 0.90 [0.75 to 1.08]), episiotomy (126 [11.4%] vs 68 [12.3%]; RR 0.93 [0.70 to 1.23]), instrumental birth (139 [12.6%] vs 79 [14.3%]; RR 0.88 [0.68 to 1.14]), Apgar scores < 8 (10 [0.9%] vs 9 [1.6%]; RR 0.56 [0.23 to 1.36]), postpartum haemorrhage (144 [13.1%] vs 75 [13.6%]; RR 0.96 [0.74 to 1.25]); breastfeeding initiation (616 [55.9%] vs 317 [57.4%]; RR 0.97 [0.89 to 1.06]). MLU women were significantly less likely to have continuous electronic fetal monitoring (397 [36.1%] vs 313 [56.7%]; RR 0.64 [0.57 to 0.71]), or augmentation of labour (436 [39.6%] vs 314 [56.9%]; RR 0.50 [0.40 to 0.61]).

CONCLUSIONS

Midwife-led care, as practised in this study, is as safe as consultant-led care and is associated with less intervention during labour and delivery.

A modified fetal heart rate tracing interpretation system for prediction of cesarean section

OBJECTIVE

To investigate whether a modified version of the 2008 National Institute of Child Health and Human Development (NICHD) interpretation system upon admission decreases cesarean delivery risk.

METHODS

This retrospective cohort study ascribed a modified category to the first 30 min of fetal heart rate (FHR) tracings in labor. Category I was divided into two subsets (Ia and Ib) by the presence of accelerations. Category II was divided into four subsets (IIa-IId) based on baseline FHR, variability, response to stimulation and decelerations. Log-binomial regression was used to calculate risk ratios (RR) and 95% confidence intervals (CI).

RESULTS

A category was ascribed to 910 women. Most FHR tracings were Category Ia (65.8%), Ib (7.7%), IIb (11.8%) and IId (14.0%). Category Ib tracings (fewer than two accelerations) were 2.26 (95% CI: 1.13-4.52) times more likely to result in cesarean delivery for abnormal FHR tracing than Category Ia tracings. A similar increase in risk was seen when comparing Category IIb and Category IId with Category Ia.

CONCLUSION

Application of a modified version of the 2008 NICHD FHR interpretation system to the initial 30 min of labor can identify women at increased risk of cesarean delivery for abnormal FHR tracing.

Glial fibrillary acidic protein as a biomarker for neonatal hypoxic-ischemic encephalopathy treated with whole-body cooling

OBJECTIVE

Glial fibrillary acidic protein (GFAP) is specific to astrocytes in the central nervous system. We hypothesized that serum GFAP would be increased in neonates with hypoxic-ischemic encephalopathy (HIE) treated with whole-body cooling.

STUDY DESIGN

We measured GFAP at birth and daily for up to 7 days for neonates in the intensive care unit. We compared neonates with HIE treated with whole-body cooling to gestational age-matched controls without neurological injury and neonates with HIE by brain abnormalities on magnetic resonance imaging (MRI).

RESULTS

Neonates with HIE had increased GFAP levels compared with controls. Neonates with HIE and abnormal brain imaging had elevated GFAP levels compared with neonates with HIE and normal imaging.

CONCLUSION

Serum GFAP levels during the first week of life were increased in neonates with HIE and were predictive of brain injury on MRI. Biomarkers such as GFAP could help triage neonates with HIE to treatment, measure treatment efficacy, and provide prognostic information.

Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States

OBJECTIVE

To examine the association between electronic fetal heart rate monitoring and neonatal and infant mortality, as well as neonatal morbidity.

STUDY DESIGN

We used the United States 2004 linked birth and infant death data. Multivariable log-binomial regression models were fitted to estimate risk ratio for association between electronic fetal heart rate monitoring and mortality, while adjusting for potential confounders.

RESULTS

In 2004, 89% of singleton pregnancies had electronic fetal heart rate monitoring. Electronic fetal heart rate monitoring was associated with significantly lower infant mortality (adjusted relative risk, 0.75); this was mainly driven by the lower risk of early neonatal mortality (adjusted relative risk, 0.50). In low-risk pregnancies, electronic fetal heart rate monitoring was associated with decreased risk for Apgar scores <4 at 5 minutes (relative risk, 0.54); in high-risk pregnancies, with decreased risk of neonatal seizures (relative risk, 0.65).

CONCLUSION

In the United States, the use of electronic fetal heart rate monitoring was associated with a substantial decrease in early neonatal mortality and morbidity that lowered infant mortality.

Electronic fetal monitoring: past, present, and future

Electronic fetal monitoring (EFM) using cardiotocography is a common tool used during labor and delivery for assessment of fetal well-being. It has largely replaced the use of intermittent auscultation and fetal scalp pH sampling. However, data suggesting improved clinical outcomes with the use of EFM are sparse. In this review, the history of EFM is revisited from its inception in the 1960s to current practice, interpretations, and future research goals.

Midwives' and doctors' attitudes towards the use of the cardiotocograph machine

The appropriate use of the cardiotocograph (CTG) machine in the clinical setting is an issue of concern for midwives and doctors.

OBJECTIVE

To examine midwives and doctors attitudes towards the use of the CTG machine in labour ward practice.

BACKGROUND

this small study provides new insight into the attitudes of doctor and midwives towards the use of CTG.

DESIGN

An exploratory descriptive design that used a combination of qualitative and quantitative approaches. A valid and reliable tool designed by Sinclair (2001) was used to measure the attitudes of doctors and midwives towards CTG usage. In addition, follow-up semi-structured interviews with doctors and midwives were conducted.

SETTING

A maternity unit in Northern Ireland.

PARTICIPANTS

Participants selected had worked in the labour ward within the last year (n = 56 midwives; n = 19 doctors). Six midwives and two doctors were randomly selected to participate in the interviews.

FINDINGS

The study demonstrated a favourable disposition towards the use of CTG machines with 72.5% (n = 29) of respondents indicating that they viewed CTG technology positively and 87.5% (n = 25) indicating they were confident about their skill in interpreting CTG tracings. The majority of the respondents (60.0%, n = 24) felt that their training adequately prepared them for using CTGs. The illustrative accounts provided by the respondents demonstrated a predominant belief that CTG technology continues to have a role in monitoring and detecting abnormalities in the fetal heart rate but this role is limited by how well the CTG is used and interpreted. The interviews confirmed the data obtained from the questionnaires and revealed a number of professional needs and concerns relating to CTG usage.

IMPLICATIONS FOR PRACTICE

The implication of this study may be focused on addressing the training needs of students, newly qualified staff and regular updates for employed staff. There was some concern that this technology may be deskilling staff and therefore there is a need to improve confidence levels in using alternatives to this type of fetal monitoring.

Electronic fetal monitoring as a public health screening program: the arithmetic of failure

Electronic fetal monitoring has failed as a public health screening program. Nevertheless, most of the four million low-risk women giving birth in the United States each year continue to undergo this screening. The failure of this program should have been anticipated and thus avoided had the accepted principles of screening been considered before its introduction. All screening tests have poor positive predictive value when searching for rare conditions such as fetal death in labor or cerebral palsy. This problem is aggravated when the screening test does not have good validity as is the case with electronic fetal monitoring. Because of low-prevalence target conditions and mediocre validity, the positive predictive value of electronic fetal monitoring for fetal death in labor or cerebral palsy is near zero. Stated alternatively, almost every positive test result is wrong. To avoid such costly errors in the future, the prerequisites for any screening program must be fulfilled before the program is begun.

Neonatal outcomes and operative vaginal delivery versus cesarean delivery

We compared outcomes for neonates with forceps-assisted, vacuum-assisted, or cesarean delivery in the second stage of labor. This is a secondary analysis of a randomized trial in laboring, low-risk, nulliparous women at >or=36 weeks' gestation. Neonatal outcomes after use of forceps, vacuum, and cesarean were compared among women in the second stage of labor at station +1 or below (thirds scale) for failure of descent or nonreassuring fetal status. Nine hundred ninety women were included in this analysis: 549 (55%) with an indication for delivery of failure of descent and 441 (45%) for a nonreassuring fetal status. Umbilical cord gases were available for 87% of neonates. We found no differences in the base excess (P = 0.35 and 0.78 for failure of descent and nonreassuring fetal status) or frequencies of pH below 7.0 (P = 0.73 and 0.34 for failure of descent and nonreassuring fetal status) among the three delivery methods. Birth outcomes and umbilical cord blood gas values were similar for those neonates with a forceps-assisted, vacuum-assisted, or cesarean delivery in the second stage of labor. The occurrence of significant fetal acidemia was not different among the three delivery methods regardless of the indication.

Strength of association between umbilical cord pH and perinatal and long term outcomes: systematic review and meta-analysis

OBJECTIVE

To evaluate the association between umbilical cord pH at birth and long term outcomes.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline (1966-August 2008), Embase (1980-August 2008), the Cochrane Library (2008 issue 8), and Medion, without language restrictions; reference lists of selected articles; and contact with authors.

STUDY SELECTION

Studies in which cord pH at birth was compared with any neonatal or long term outcome. Cohort and case-control designs were included.

RESULTS

51 articles totalling 481 753 infants met the selection criteria. Studies varied in design, quality, outcome definition, and results. Meta-analysis carried out within predefined groups showed that low arterial cord pH was significantly associated with neonatal mortality (odds ratio 16.9, 95% confidence interval 9.7 to 29.5, I(2)=0%), hypoxic ischaemic encephalopathy (13.8, 6.6 to 28.9, I(2)=0%), intraventricular haemorrhage or periventricular leucomalacia (2.9, 2.1 to 4.1, I(2)=0%), and cerebral palsy (2.3, 1.3 to 4.2, I(2)=0%).

CONCLUSIONS

Low arterial cord pH showed strong, consistent, and temporal associations with clinically important neonatal outcomes that are biologically plausible. These data can be used to inform clinical management and justify the use of arterial cord pH as an important outcome measure alongside neonatal morbidity and mortality in obstetric trials.

[Cerebral palsy and perinatal asphyxia (I--diagnosis)]

Cerebral palsy (CP) is a group of disorders of the development of movement and posture, causing activity limitations, that are attributed to nonprogressing disturbances that occurred in the developing fetal or infant brain. The motor abnormalies are often accompanied by disturbances of sensation, perception, cognition, behavior and/or by a seizure disorder. The prevalence of CP has not decreased in developed countries over the past 30 years, despite the widespread use of electronic fetal heart rate monitoring and a 5- to 6-fold increase in the cesarean delivery rate. In the term newborn, CP may be attributed to perinatal asphyxia in case of metabolic acidosis in the cord blood (pH<7,00 and base deficit>12 mmol/L), followed by a moderate or severe neonatal encephalopathy within 24 hours and a further neurological impairement characterized by spastic quadriplegia and dyskinesia/dystonia. Dating the time of fetal asphyxia during delivery is possible when there are acute catastrophic complications during labor and unexpected acute or progressive fetal heart rate anomalies after a normal admission test, when there is a need for intensive neonatal resuscitation, a multi-organ failure within 72 hours of birth and visualization of acute non focal cerebral abnormalities, mainly by early magnetic resonance imaging (MRI). MRI sequences show either a brain-damaged pattern of the central basal ganglia, thalami and posterior limbs of internal capsules with relative cortical sparing, in acute, near-total asphyxial insults manifested by a continuous bradycardia or a pattern of cortical injury in the watershed zones and relative sparing of the central grey matter, in prolonged partial asphyxia, manifested by late or atypical variable decelerations with progressive fetal tachycardia, loss of reactivity and absent fluctuation. Prolongation of either type of asphyxial insult results in more global brain damage. In order to differentiate a CP occurring after perinatal asphyxia from other neurological sequelae in relation with infection, hemorrhage, stroke, malformations, genetic or metabolic diseases, it is essential that a definitive information from the brain by MRI and an extensive histological examination of the placenta are at disposal.

A systematic review of the role of intrapartum hypoxia-ischemia in the causation of neonatal encephalopathy

The object of this review was to determine the incidence, morbidity, and mortality of an umbilical arterial pH < 7.0; the incidence of hypoxic-ischemic encephalopathy; and the proportion of cerebral palsy associated with intrapartum hypoxia-ischemia in nonanomalous term infants. A systematic review of the English language literature on the association between intrapartum hypoxia-ischemia and neonatal encephalopathy was conducted by using Pubmed and Embase. For nonanomalous term infants, the incidence of an umbilical arterial pH < 7.0 at birth is 3.7 of 1000, of which 51 of 297 (17.2%) survived with neonatal neurologic morbidity, 45 of 276 (16.3%) had seizures, and 24 of 407 (5.9%) died during the neonatal period. The incidence of neonatal neurologic morbidity and mortality for term infants born with cord pH < 7.0 was 23.1%. The incidence of hypoxic-ischemic encephalopathy is 2.5 of 1000 live births. The proportion of cerebral palsy associated with intrapartum hypoxia-ischemia is 14.5%. The vast majority of cases of cerebral palsy in nonanomalous term infants are not associated with intrapartum hypoxia-ischemia.

Is cerebral palsy preventable?

PURPOSE OF REVIEW

To use evidence of good medical quality to update information on strategies for prevention of cerebral palsy, and on the success of these preventive efforts to date.

RECENT FINDINGS

Causes of cerebral palsy, and therefore promising approaches to prevention, differ by gestational age group and by clinical subtype. Neuroimaging and neuropathology indicate the importance of white matter disorders and of ischemic stroke in cerebral palsy; birth asphyxia, congenital malformations, placental pathology, and genetic variants also contribute to cerebral palsy risk. Multiplicity of risk factors markedly increases risk. Recent studies indicate that mild hypothermia lessens cerebral palsy risk in term infants with moderate neonatal encephalopathy, and the possibility that administration of magnesium sulphate to women in preterm labor may aid in primary prevention of cerebral palsy in very preterm infants.

SUMMARY

Past efforts to prevent cerebral palsy have not had the benefits sought, but recent results provide new hope and new challenges.

Fetal health assessment using prenatal diagnostic techniques

PURPOSE OF REVIEW

The assessment of fetal health has occupied our professional attention for many years. As the development of technologies for prenatal diagnostic techniques has progressed, applications of such technologies have aided in the overall assessment of fetal well-being.

RECENT FINDINGS

Fetal heart-rate monitoring remains the main form of fetal assessment for high-risk pregnancies. The additional assessments afforded by the analysis of ST and T-wave changes of the fetal electrocardiogram hold promise for improving the predictive value of fetal heart-rate assessments. Ultrasound has been invaluable for assessment of fetal anatomy, and the use of Doppler ultrasound has given insight into fetal cardiovascular responses to such conditions as intrauterine growth restriction and fetal anemia caused by red blood cell alloimmunization.

SUMMARY

As prenatal diagnostic techniques evolve, their application to the assessment of fetal well-being offers insight into pathophysiologic mechanisms of fetal disease, innovative tools to assess fetal health, and fertile ground for future investigation.