Obstetric characteristics and fetal heart rate patterns of infants who convulse during the newborn period

Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour

BACKGROUND

Cardiotocography (CTG) records changes in the fetal heart rate and their temporal relationship to uterine contractions. The aim is to identify babies who may be short of oxygen (hypoxic) to guide additional assessments of fetal wellbeing, or determine if the baby needs to be delivered by caesarean section or instrumental vaginal birth. This is an update of a review previously published in 2013, 2006 and 2001.

OBJECTIVES

To evaluate the effectiveness and safety of continuous cardiotocography when used as a method to monitor fetal wellbeing during labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (30 November 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials involving a comparison of continuous cardiotocography (with and without fetal blood sampling) with no fetal monitoring, intermittent auscultation intermittent cardiotocography.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, quality and extracted data from included studies. Data were checked for accuracy.

MAIN RESULTS

We included 13 trials involving over 37,000 women. No new studies were included in this update.One trial (4044 women) compared continuous CTG with intermittent CTG, all other trials compared continuous CTG with intermittent auscultation. No data were found comparing no fetal monitoring with continuous CTG. Overall, methodological quality was mixed. All included studies were at high risk of performance bias, unclear or high risk of detection bias, and unclear risk of reporting bias. Only two trials were assessed at high methodological quality.Compared with intermittent auscultation, continuous cardiotocography showed no significant improvement in overall perinatal death rate (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.59 to 1.23, N = 33,513, 11 trials, low quality evidence), but was associated with halving neonatal seizure rates (RR 0.50, 95% CI 0.31 to 0.80, N = 32,386, 9 trials, moderate quality evidence). There was no difference in cerebral palsy rates (RR 1.75, 95% CI 0.84 to 3.63, N = 13,252, 2 trials, low quality evidence). There was an increase in caesarean sections associated with continuous CTG (RR 1.63, 95% CI 1.29 to 2.07, N = 18,861, 11 trials, low quality evidence). Women were also more likely to have instrumental vaginal births (RR 1.15, 95% CI 1.01 to 1.33, N = 18,615, 10 trials, low quality evidence). There was no difference in the incidence of cord blood acidosis (RR 0.92, 95% CI 0.27 to 3.11, N = 2494, 2 trials, very low quality evidence) or use of any pharmacological analgesia (RR 0.98, 95% CI 0.88 to 1.09, N = 1677, 3 trials, low quality evidence).Compared with intermittent CTG, continuous CTG made no difference to caesarean section rates (RR 1.29, 95% CI 0.84 to 1.97, N = 4044, 1 trial) or instrumental births (RR 1.16, 95% CI 0.92 to 1.46, N = 4044, 1 trial). Less cord blood acidosis was observed in women who had intermittent CTG, however, this result could have been due to chance (RR 1.43, 95% CI 0.95 to 2.14, N = 4044, 1 trial).Data for low risk, high risk, preterm pregnancy and high-quality trials subgroups were consistent with overall results. Access to fetal blood sampling did not appear to influence differences in neonatal seizures or other outcomes.Evidence was assessed using GRADE. Most outcomes were graded as low quality evidence (rates of perinatal death, cerebral palsy, caesarean section, instrumental vaginal births, and any pharmacological analgesia), and downgraded for limitations in design, inconsistency and imprecision of results. The remaining outcomes were downgraded to moderate quality (neonatal seizures) and very low quality (cord blood acidosis) due to similar concerns over limitations in design, inconsistency and imprecision.

AUTHORS' CONCLUSIONS

CTG during labour is associated with reduced rates of neonatal seizures, but no clear differences in cerebral palsy, infant mortality or other standard measures of neonatal wellbeing. However, continuous CTG was associated with an increase in caesarean sections and instrumental vaginal births. The challenge is how best to convey these results to women to enable them to make an informed decision without compromising the normality of labour.The question remains as to whether future randomised trials should measure efficacy (the intrinsic value of continuous CTG in trying to prevent adverse neonatal outcomes under optimal clinical conditions) or effectiveness (the effect of this technique in routine clinical practice).Along with the need for further investigations into long-term effects of operative births for women and babies, much remains to be learned about the causation and possible links between antenatal or intrapartum events, neonatal seizures and long-term neurodevelopmental outcomes, whilst considering changes in clinical practice over the intervening years (one-to-one-support during labour, caesarean section rates). The large number of babies randomised to the trials in this review have now reached adulthood and could potentially provide a unique opportunity to clarify if a reduction in neonatal seizures is something inconsequential that should not greatly influence women's and clinicians' choices, or if seizure reduction leads to long-term benefits for babies. Defining meaningful neurological and behavioural outcomes that could be measured in large cohorts of young adults poses huge challenges. However, it is important to collect data from these women and babies while medical records still exist, where possible describe women's mobility and positions during labour and birth, and clarify if these might impact on outcomes. Research should also address the possible contribution of the supine position to adverse outcomes for babies, and assess whether the use of mobility and positions can further reduce the low incidence of neonatal seizures and improve psychological outcomes for women.

Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour

BACKGROUND

Cardiotocography (known also as electronic fetal monitoring), records changes in the fetal heart rate and their temporal relationship to uterine contractions. The aim is to identify babies who may be short of oxygen (hypoxic), so additional assessments of fetal well-being may be used, or the baby delivered by caesarean section or instrumental vaginal birth.

OBJECTIVES

To evaluate the effectiveness of continuous cardiotocography during labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (31 December 2012) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials involving a comparison of continuous cardiotocography (with and without fetal blood sampling) with (a) no fetal monitoring, (b) intermittent auscultation (c) intermittent cardiotocography.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, quality and extracted data from included studies.

MAIN RESULTS

Thirteen trials were included with over 37,000 women; only two were judged to be of high quality.Compared with intermittent auscultation, continuous cardiotocography showed no significant improvement in overall perinatal death rate (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.59 to 1.23, n = 33,513, 11 trials), but was associated with a halving of neonatal seizures (RR 0.50, 95% CI 0.31 to 0.80, n = 32,386, nine trials). There was no significant difference in cerebral palsy rates (RR 1.75, 95% CI 0.84 to 3.63, n = 13,252, two trials). There was a significant increase in caesarean sections associated with continuous cardiotocography (RR 1.63, 95% CI 1.29 to 2.07, n = 18,861, 11 trials). Women were also more likely to have an instrumental vaginal birth (RR 1.15, 95% CI 1.01 to 1.33, n = 18,615, 10 trials).Data for subgroups of low-risk, high-risk, preterm pregnancies and high-quality trials were consistent with overall results. Access to fetal blood sampling did not appear to influence the difference in neonatal seizures nor any other prespecified outcome.

AUTHORS' CONCLUSIONS

Continuous cardiotocography during labour is associated with a reduction in neonatal seizures, but no significant differences in cerebral palsy, infant mortality or other standard measures of neonatal well-being. However, continuous cardiotocography was associated with an increase in caesarean sections and instrumental vaginal births. The challenge is how best to convey these results to women to enable them to make an informed choice without compromising the normality of labour.

The 30 minutes decision-to-delivery interval for ‘urgent’ caesarean sections: An elusive target

The aim of this audit was to evaluate whether the '30 minute decision-to-delivery interval' for 'urgent' caesarean section has shown consistent improvement with repeated audit within this unit. The audit dataset comprised a random sample of all urgent caesarean sections carried out in 2004 classified as 'urgent', i.e. to be completed in 30 min. Nearly one-third of caesarean sections recorded on the delivery suite database as 'urgent' were incorrectly coded. A personal review of case notes was undertaken to ensure accurate data capture. Delivery suite data was analysed by post-hoc modelling of a 'normal' (Gaussian) distribution. The proportion of true 'urgent' caesarean sections completed in 30 min was 50% and some 90% of women were delivered within 40 min. The data were normally distributed, with non-random events, accounted for 25% of the variability. A model for 'urgent' caesarean section, accommodating random and non-random factors closely matched the audit data. We conclude that non-random, institutional, factors reflecting overall delivery suite activity adversely effect the decision-to-delivery interval regardless of the performance of personnel and processes within a delivery suite.

Early-onset neonatal seizures: types, risk factors and short-term outcome

In a large majority of term newborns, early-onset neonatal seizures (EONS) are believed to relate to perinatal risk factors.

AIM

To identify risk factors for EONS.

METHODS

Among a cohort of 1293 newborns admitted over a period of 2 years to the neonatal intensive care unit of Tikur Anbasa Hospital, Addis Ababa, 93 had seizures. The case control study method was used to identify risk factors associated with EONS. Univariate analysis was used to further examine risk factors after adjusting for the effect of severe perinatal asphyxia (Apgar < or = 3).

RESULTS

A total of 78 (85%) term newborns had EONS. Hypoxic-ischaemic encephalopathy (OR 3.46, 95% CI 2.74-7.42) and shock (OR 2.53, 95% CI 1.51-4.76) were significantly associated with EONS. Multifocal clonic (66%) followed by focal clonic (22%) were the most common types of EONS. Nine (11%) of the newborns with EONS died. During follow-up, 37 (53%) of the 69 surviving newborns with EONS had psychomotor delay with or without neurological deficit.

CONCLUSION

Hypoxic-ischaemic encephalopathy and shock are important causes of EONS.

Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour

BACKGROUND

Cardiotocography (sometimes known as electronic fetal monitoring), records changes in the fetal heart rate and their temporal relationship to uterine contractions. The aim is to identify babies who may be short of oxygen (hypoxic), so additional assessments of fetal well-being may be used, or the baby delivered by caesarean section or instrumental vaginal birth.

OBJECTIVES

To evaluate the effectiveness of continuous cardiotocography during labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (March 2006), CENTRAL (The Cochrane Library 2005, Issue 4), MEDLINE (1966 to December 2005), EMBASE (1974 to December 2005), Dissertation Abstracts (1980 to December 2005) and the National Research Register (December 2005).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials involving a comparison of continuous cardiotocography (with and without fetal blood sampling) with (a) no fetal monitoring, (b) intermittent auscultation (c) intermittent cardiotocography.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed eligibility, quality and extracted data.

MAIN RESULTS

Twelve trials were included (over 37,000 women); only two were high quality. Compared to intermittent auscultation, continuous cardiotocography showed no significant difference in overall perinatal death rate (relative risk (RR) 0.85, 95% confidence interval (CI) 0.59 to 1.23, n = 33,513, 11 trials), but was associated with a halving of neonatal seizures (RR 0.50, 95% CI 0.31 to 0.80, n = 32,386, nine trials) although no significant difference was detected in cerebral palsy (RR 1.74, 95% CI 0.97 to 3.11, n = 13,252, two trials). There was a significant increase in caesarean sections associated with continuous cardiotocography (RR 1.66, 95% CI 1.30 to 2.13, n =18,761, 10 trials). Women were also more likely to have an instrumental vaginal birth (RR 1.16, 95% CI 1.01 to 1.32, n = 18,151, nine trials). Data for subgroups of low-risk, high-risk, preterm pregnancies and high quality trials were consistent with overall results. Access to fetal blood sampling did not appear to influence the difference in neonatal seizures nor any other prespecified outcome.

AUTHORS' CONCLUSIONS

Continuous cardiotocography during labour is associated with a reduction in neonatal seizures, but no significant differences in cerebral palsy, infant mortality or other standard measures of neonatal well-being. However, continuous cardiotocography was associated with an increase in caesarean sections and instrumental vaginal births. The real challenge is how best to convey this uncertainty to women to enable them to make an informed choice without compromising the normality of labour.

Spinal motor neuron excitability in newborns following fetal distress: sub-clinical depression revealed by soleus H-reflex

OBJECTIVE

To explore possible spinal cord dysfunction in clinically unaffected newborns emerging from fetal distress, using H-Reflex.

METHODS

This cross-sectional study comprised 48 full-term newborn infants investigated between 8h and 10 days after birth. Twenty-one (21) had fetal distress defined by late-decelerations in fetal heart rate, out of which 11 had also meconium release in utero; 5 passed meconium in utero with normal FHR patterns; and 22 normal controls had uneventful birth. All had normal birth-weight and Apgar scores. All were found normal on neurological examination, except one showing hypotonia following fetal distress. Soleus H-reflex was studied in right lower limb.

RESULTS

Newborns delivered with fetal distress showed significant reduction in H-reflex excitability (H/M ratio) within 2 days of birth. Tests performed closer to the birth event revealed more severe depression. Meconium did not contribute to this effect.

CONCLUSIONS

Fetal distress can lead to transient, subclinical depression of spinal motoneurons in the newborn.

SIGNIFICANCE

This neonatal H-reflex study focuses on excitability of a spinal motoneuron pool rather than conduction parameters (reflecting myelination) available in literature. It reveals excitability changes missed on clinical examination of newborns apparently unaffected by intrapartum hypoxic-ischemic spells. It also draws attention towards spinal cord dysfunction in birth-hypoxia.

Comparison of intrapartum fetal heart rate tracings in patients with neonatal seizures vs. no seizures: what are the differences?

OBJECTIVE

To determine which intrapartum fetal heart rate parameters in the presence of severe neonatal acidosis (pH < 7.0) appropriately predicts the development of neonatal seizures in the context of hypoxic ischemic encephalopathy (HIE).

METHODS

The intrapartum fetal heart rate tracings of 25 neonates who developed neonatal seizures secondary to HIE were compared with 25 matched neonates with similar pH and gestational age who did not develop seizures. All patients had at least 2 hours of intrapartum fetal heart rate patterns available for review. We compared the fetal heart rate parameters of prolonged deceleration, variable and late decelerations, variability, accelerations, fetal heart rate baseline and duration of the fetal heart rate abnormality. Comparison between the groups was done using chi-square for nominal data and student t-tests for continuous data.

RESULTS

Neonates with seizures 2 degrees HIE had a significantly longer duration of abnormal fetal heart rate patterns (72 +/- 12 minutes vs 48 +/- 12 minutes, p < 0.001).

DISCUSSION

This study demonstrated that in the setting of neonatal acidosis the development of seizures is related to the period of stress (duration of the abnormal fetal heart rate pattern).

The decision-to-delivery interval for emergency caesarean section: is 30 minutes a realistic target?

OBJECTIVE

To evaluate whether a 30-minute decision-to-delivery interval is a realistic target for emergency caesarean section.

DESIGN

An audit of all emergency caesarean sections over five separate periods.

SETTING

A district general hospital.

PARTICIPANTS

Five groups of women (343 women) with an indication for emergency caesarean section.

METHODS

Following an initial survey, a structured time sheet was introduced, followed by four other surveys to complete the audit cycle.

MAIN OUTCOME MEASURE

The proportion of caesarean sections where the decision-to-delivery interval was achieved within 30 minutes. The reasons for delay.

RESULTS

In the first survey of 73 emergency caesarean sections, the time to deliver the infant exceeded 30 minutes in 47 women (64%). The main sources of delay were transferring the women to the operating theatre and starting the anaesthetic. After the introduction of a structured time sheet, there was an improvement with each survey, but the target of 30 minutes was reached in only 71% of caesarean sections in the final survey.

CONCLUSIONS

The introduction of a time sheet can improve the decision-to-delivery interval for emergency caesarean section; however, a universal standard of 100% in 30 minutes is unrealistic.

The relationship between nucleated red blood cell counts and early-onset neonatal seizures

OBJECTIVE

This study was undertaken to better define the timing of neurologic insult in neonates with early-onset seizures through evaluation of neonatal nucleated red blood cell levels.

STUDY DESIGN

Medical records and the International Classification of Diseases, Ninth Revision codes were used to identify all term neonates with neonatal convulsions who were delivered at our institution (January 1, 1990-December 31, 1995). Each neonate with early-onset seizures was matched to the next 3 neonates who met the following criteria: gestational age > or =37 weeks, no early-onset seizures, birth weight > or =800 g, umbilical artery pH > or =7.25, and a 5-minute Apgar score >7. Demographic characteristics, clinical factors, and mean initial nucleated red blood cell counts were compared between groups.

RESULTS

During the 6-year study period, there were a total of 36, 490 singleton term deliveries of infants who were alive at birth. Forty-five (0.1%) of these neonates had early-onset seizures. Thirty neonates with early-onset seizures met the inclusion criteria. Mean nucleated red blood cell counts (number of nucleated red blood cells per 100 white blood cells) for neonates with early-onset seizures were significantly increased compared with those of control neonates (18.4 +/- 22.0 vs 4.6 +/- 4.5; P <.0008).

CONCLUSIONS

Our findings are suggestive of the hypothesis that neurologic injury leading to early-onset seizures often occurs before the intrapartum period.

Antecedents of neonatal encephalopathy with fetal acidaemia at term

OBJECTIVE

To identify the relative contribution of antenatal hypoxia, obstetric catastrophe during labour and fetal monitoring practice to the occurrence of neonatal encephalopathy associated with acidaemia at term.

DESIGN

Prospective study.

SETTING

Tertiary referral hospital in Auckland, New Zealand.

SAMPLE

Twenty-two term babies born between January 1996 and October 1997 with umbilical artery pH < or = 7.09 (median 6.88) or 5 minute Apgar score < 7 (median 5.0), and moderate to severe encephalopathy within five hours of birth.

METHODS

Antenatal and intrapartum events and fetal heart rate monitoring practice were reviewed by an experienced obstetrician.

RESULTS

More than half the cases were associated with events beyond the control of the clinician: 5 of 22 (23%) had evidence of antenatal hypoxia and 5 of 22 (23%) experienced an obstetric catastrophe during labour. Use of continuous fetal monitoring techniques or the interpretation of fetal heart rate changes was suboptimal in 8 of 12 cases. Continuous monitoring was not performed at all in three cases. All pregnancies were of either low or medium risk; none had proteinuric hypertension and no case was breech, small for gestational age or had a gestational age > or = 42 weeks.

CONCLUSIONS

A significant proportion of babies with encephalopathy associated with acidaemia at term experienced either antenatal hypoxia or catastrophic events beyond the control of the clinician. Further improvements in obstetric care will require greater vigilance in low to medium risk pregnancies and improved fetal monitoring practice during both induction and labour.

Perinatal asphyxia: assessing its causal role and timing

Perinatal asphyxia, whether prenatal, intrapartum, or neonatal is thought to be a significant contributor to newborn morbidity and mortality as well as long-term neurological deficits. Development of an intrapartum tool/test that can reliably identify and discriminate between varying degrees of fetal acidemia and suggest whether it is respiratory or metabolic in nature would be highly desirable. This article critically reviews the available experience with the currently available monitoring techniques and the significance of abnormalities of fetal and intrapartum measurements with respect to the predictive value of the observations available to the clinician.

Perinatal observations in forty-eight neurologically impaired term infants

OBJECTIVE

Our goal was to review the perinatal characteristics of 48 singleton term infants with central nervous system neurologic impairment.

STUDY DESIGN

Medical records were retrospectively reviewed for maternal characteristics, prenatal and intrapartum care patterns, neonatal course, and long-term outcome. Those patients without evidence of an obvious acute asphyxial event, traumatic delivery, or preterm birth were excluded. The study population was then subclassified according to the admission fetal heart rate pattern.

RESULTS

Of these 48 term infants the admission fetal heart rate pattern was nonreactive in 33 (69%) and reactive in 15 (31%). Maternal characteristics, prenatal care, and long-term outcome were statistically similar between the two groups. However, the nonreactive group exhibited significantly more characteristics consistent with a prior asphyxial event: thick "old" meconium, "fixed" nonreactive baseline fetal heart rate, meconium-stained skin, and meconium aspiration syndrome. In contrast, in the reactive group a fetal heart rate pattern developed that was consistent with Hon's theory for intrapartum asphyxia and manifested by a prolonged tachycardia in association with persistent nonreactivity, diminished fetal heart rate variability, and fetal heart rate decelerations.

CONCLUSIONS

Among fetuses later found to be neurologically impaired, a persistent nonreactive fetal heart rate tracing obtained from admission to delivery appears to be evidence of prior neurologic injury.

Maternal-fetal HLA sharing and risk of newborn encephalopathy and seizures: a pilot study

A pilot case-control study was done to collect data on whether susceptibility to newborn encephalopathy and neonatal seizures is influenced by the degree of maternal-fetal sharing of HLA antigens. Cases included 13 infants with moderate or severe newborn encephalopathy and seven infants with neonatal seizures but no other signs of encephalopathy. Controls were neurologically normal infants matched to cases by date of birth, sex, race, and payment status. Infants and their mothers were typed for HLA-A, -B, -DR, and -DQ antigens. The observed frequency of sharing of maternal antigens was greater than expected (ie, 0.5) for cases compared to controls at the HLA-B, -DR, and -DQ loci but not for HLA-A. The risk of neurologic problems in the neonatal period was increased 6.3 times when there was more than one match at the HLA-DR or -DQ locus. Placental abnormalities were noted at delivery only among cases, and the mean placental weight in cases was 598 g versus 695 g in controls. Further studies with sample sizes sufficiently large to statistically test this hypothesis are needed.

The paradox of electronic fetal monitoring: more data may not enable us to predict or prevent infant neurologic morbidity

Electronic fetal heart rate monitoring has been used to identify periods of fetal risk, with the hope that clinical intervention would avoid the potential for perinatal death or neurologic damage. A literature review of 10 infant studies failed to document fetal heart rate patterns associated with neurologic injury or protocols for intervention to avoid neurologic injury. A separate analysis of fetal heart rate patterns from 55 brain-damaged infants failed to find consistent patterns that foreshadowed the observed brain injury. These findings should not be surprising, because the majority of infant brain damage occurs outside the intrapartum period and because electronic monitoring may identify times of fetal risk but was never expected to identify brain damage.

Falling incidence of hypoxic-ischaemic encephalopathy in term infants

OBJECTIVE

To examine trends in the incidence of hypoxic-ischaemic encephalopathy over a 13-year period.

DESIGN

A retrospective analysis of medical records of all infants admitted in the years 1976-1980 and 1984-1988.

SETTING

A large non-teaching district health authority in central England.

SUBJECTS

Infants admitted to a district general hospital neonatal unit with clinical features of hypoxic-ischaemic encephalopathy.

MAIN OUTCOME MEASURES

Incidence of three grades of hypoxic-ischaemic encephalopathy, handicap and mortality.

RESULTS

During the first 5-year period the overall incidence of hypoxic-ischaemic encephalopathy was 7.7 per 1000 live births with 2.6 per 1000 live births being severely affected (grades II and III). In the second 5-year period the overall incidence was 4.6 per 1000 live births with 1.8 per 1000 live births being severely affected. The difference in the overall rate is statistically significant. Of the infants with severe encephalopathy 61% had Apgar scores below 4 at 1 min and 60% were born by instrumental or operative delivery.

CONCLUSIONS

The fall in incidence of hypoxic-ischaemic encephalopathy has occurred during a period of falling perinatal mortality rate. It was instructive to find that infants born vaginally and without obstetric intervention formed a larger fraction of the severely affected infants in the later period.

The Green Bay cesarean section study. I. The physician factor as a determinant of cesarean birth rates

This study was designed to identify the determinants of cesarean birth rates. The study population included all 1030 cesarean deliveries performed on singleton pregnancies by 11 obstetricians practicing at two Green Bay hospitals from 1986 through 1988; 1076 control patients with vaginal deliveries were selected for comparison purposes. The 1030 cesarean deliveries represented 14% of the 7335 singleton deliveries that occurred during the study period. Individual physician cesarean rates ranged from 5.6% to 19.7%. Cesarean rates for physician groups ranged from 9.8% to 18%. The variances in cesarean rates among individual and groups of physicians were not attributable to patient obstetric risk factors, socioeconomic status, service status, or duration of the physician's practice. Higher cesarean rates did not result in better neonatal outcome. Individual physician practice style was the only apparent determinant of cesarean rates for the 11 obstetricians. Current cesarean rates can be substantially reduced without sacrificing fetal and newborn safety.

Birth asphyxia and the intrapartum cardiotocograph

The intrapartum cardiotocographs (CTGs) of 38 severely asphyxiated, term infants, born during a 17-month period, and those of 120 healthy term infants acting as controls were independently reviewed by three investigators who were unaware of the clinical outcome. Inter-observer agreement was good (Kappa statistic = 0.74, P less than 0.0001). The investigators found that cardiotocographic abnormalities were present in 33 of the asphyxiated infants (87%) and in 35 of the controls (29%) and predicted that the abnormalities were severe enough to lead to significant fetal metabolic acidosis at delivery in 23 asphyxiated infants (61%) and in 11 controls (9%). The differences between the two groups were highly significant (P less than 0.001). Using the traditional diagnostic criteria for fetal distress, the investigators found that fetal blood sampling was indicated in 58% of cases in the asphyxia group and in 20% of controls but was only performed in 16% of asphyxiated infants and in 8% of controls. Furthermore, the median response times of delivery suite staff for abnormal fetal heart rate patterns were similar whether the FHR changes, classified using Krebs' CTG scoring system, were moderate or severe: 80 min and 90 min, respectively. These findings suggest that interpretation of the intrapartum CTG continues to pose major problems for practising obstetricians.

What is fetal distress?

Fetal distress is a widely used but poorly defined term. This confusion of definition compounds the difficulty of making an accurate diagnosis and initiating appropriate treatment. The fetus reacts at the onset of asphyxia with a remarkable series of responses, primarily a complexly regulated redistribution of blood flow that serves to limit the deleterious effects of oxygen limitation in vital organs. This enables the fetus to survive asphyxia intact unless the insult is profound or prolonged. The most common asphyxial stresses imposed on the fetus during labor are insufficiency of uterine blood flow, or insufficiency of umbilical blood flow, and occasionally decrease in uterine arterial oxygenation. Each of these stresses produces characteristic fetal heart rate patterns: late decelerations, variable decelerations, or prolonged bradycardia. There is strong evidence that the presence of normal fetal heart rate variability represents normal central nervous system integrity, including adequate oxygenation. A decrease or loss of variability in the presence of these patterns is a sign that the physiologic compensations are overwhelmed as a result of the severity of asphyxia. Knowledge of the fetal responses to asphyxia, together with the known evolution of fetal heart rate patterns during asphyxia, should allow a more accurate definition of the onset of unacceptable asphyxia, and more rational management and timing of intervention.

Predicting neonatal morbidity after perinatal asphyxia: a scoring system

Predicting immediate neonatal morbidity after perinatal asphyxia has been difficult. A review of asphyxiated neonates greater than or equal to 36 weeks' gestation admitted to The Children's Hospital Newborn Intensive Care Unit in 1983 was conducted to devise a scoring system that would rapidly predict organ dysfunction observed in the immediate neonatal period. Comparison of potential score components to morbidity by multiple regression analysis yielded significant association with abnormalities in fetal heart rate monitoring, the 5-minute Apgar score, and neonatal base deficit. A scoring system was devised whose sensitivity (93.8%) and specificity (81.3%) were more predictive than any of its individual components. Prospective analysis in a similar population in 1984 validated its ability to distinguish severe from moderate morbidity after asphyxia. Positive predictive value for the score in the combined study groups (n = 98) was 79% and the negative predictive value was 83%. The scoring system may offer a rapid and accurate prediction of organ dysfunction in the immediate neonatal period after asphyxia.

The human fetal auditory evoked potential

The brain-stem auditory evoked potential (BAEP), a sensitive test of the functional status of the neonatal brain, has not been studied in utero since no practical technique for human fetal recording is available. We have developed a simple recording technique which allows continuous monitoring of the fetal AEP during labor. Waves I, III and V of the fetal brain-stem AEP have been consistently identified. Wave form morphology, interpeak latencies, and latency-intensity relations are similar to postnatal recordings. Middle latency potentials have also been recorded, with wave forms that correspond to the neonatal middle latency AEP.

Neonatal seizures after cesarean delivery: higher risk with labor

A study was done on the occurrence of neonatal seizures in 14,367 infants delivered by cesarean section in a perinatal region in 4 years. Although seizures occurred in 1% of all of these infants, small infants weighing less than 2500 gm at birth had the highest frequency (greater than 4%). Term infants delivered before labor (repeat cesarean section) had the lowest seizure rate (less than 0.2%), and this was a significantly lower (four times) frequency than that seen in term infants delivered by primary cesarean section. These data suggest that brain function as indexed by neonatal seizures can be adversely affected during labor.

Antecedents and outcome of very early neonatal seizures in infants born at or after term

Recent experimentally derived evidence has confirmed earlier suggestions that seizures which occur within 48 h of birth in babies born at or later than 37 completed weeks gestation are particularly likely to reflect intrapartum asphyxia. We have compared 54 cases of such seizures with 41,090 controls in a geographically defined population. Nulliparity, hydramnios, post-term pregnancy, oxytocin augmentation of labour, abnormalities of fetal heart rate and/or meconium-stained amniotic fluid, prolonged second stage of labour, emergency caesarean section, assisted vaginal delivery, low Apgar score and resuscitation at delivery and subsequent ventilatory support were all statistically significantly more common among cases than among controls. Five of the 54 babies who developed seizures died within 28 days of birth and 11 of the 49 survivors had an impairment diagnosed by 3 years of age which was usually associated with some degree of cerebral palsy. Comparison of the frequency of antecedent perinatal risk factors in the seizure babies who died, those who survived with disabilities and normal survivors failed to reveal any clear pattern.

Intrapartum fetal monitoring

From the fetal viewpoint, labour is a prolonged contraction stress test which most pass without incident. Labour also represents the obstetrician's last opportunity to influence perinatal outcome and ensure that those fetuses who have suffered chronic hypoxia antenatally are recognized promptly, so that labour is supervised in a way that does not place them at increased risk of either death or birth asphyxia. In the case of the fetus who enters labour healthy, with normal reserves, labour is managed with the same aim in mind, but with the foreknowledge that visualization of a normal volume of clear amniotic fluid and reasonable duration of labour makes the development of hypoxia and asphyxia unlikely. Those at increased risk of hypoxia should be monitored electronically, but, for the remainder, intermittent auscultation is satisfactory until labour lasts in excess of 5 hours, or if the patient requires oxytocin, or if an epidural is placed. If EFM is used, then it is important to provide adequate education in trace interpretation, with particular emphasis on the importance of short-term variability. Widespread use of EFM has provided us with an immense amount of knowledge about fetal physiology, but it is critically important for the practising obstetrician to understand that, in the low-risk patient, EFM is not more effective than IA in preventing death from asphyxia, that EFM does protect against asphyxial seizures, but that widespread use of the technique has not been associated with a significant reduction in the population of permanently handicapped infants. This information is particularly relevant in developing nations where money spent on sophisticated monitoring equipment might be better spent in other areas. From the maternal point of view, intensive fetal monitoring has profound implications by virtue of its usual effect on incidence of Caesarean birth, although the Dublin trial results, with regard to incidence of Caesarean section, emphasize the importance of considering intrapartum fetal monitoring as just one part of the overall supervision of labour. Finally, it must be emphasized that the method of fetal monitoring chosen may be strongly influenced by factors other than scientific evidence, as in the United States where the medicolegal climate is such that failure to rigorously document absence of fetal distress/true birth asphyxia may result in a harrowing lawsuit. It is a position this author has developed considerable sympathy with in recent years.