The Dublin randomized controlled trial of intrapartum fetal heart rate monitoring

Historical controversy in health technology assessment: the case of electronic fetal monitoring

Electronic fetal monitoring (EFM) was introduced in the late 1950s as an alternative to traditional auscultation by stethoscope or fetoscope in the management of labor and delivery. The new technology was seen as a valuable tool in the prevention of cerebral palsy and other adverse fetal outcomes and diffused rapidly into clinical practice. In the late 1970s, some scepticism began to be voiced about the evidence for the effectiveness of EFM. The authors published a systematic review of the evidence in 1979 that concluded that there was insufficient evidence for the effectiveness of the routine use of EFM and a clear rise in the cesarean delivery rate associated with its use. The analysis was based on a thorough review of approximately 600 books and articles, but focused heavily on the evidence of four randomized clinical trials (RCTs) that had been published. An economic analysis further underscored the importance of this issue. The report was met with harsh ad hominem criticism from clinicians both in public venues and in the medical literature. Subsequently, additional RCTs were conducted and other analyzes were published, and in 1987 the American College of Obstetricians and Gynecologists recommended that auscultation was an acceptable alternative to EFM in routine labor and delivery. Yet, today EFM continues to be the standard of practice, used in 80% of labors in this country. The most important conclusion drawn from this experience is the need to evaluate new technologies before their widespread diffusion into clinical practice.

Clinical usefulness of pulse oximetry in the fetus with non-reassuring heart rate pattern?

The objective of this study was the evaluation of intrapartum pulse oximetry as an indicator of fetal distress and the condition of the newborn during clinical routine surveillance in an University Perinatal Center. Between 1998 and 1999 pulse oximetry (SpO2) was used additionally to routine fetal monitoring by electronic fetal heart rate tracing (CTG) and fetal blood sampling (FBA) in 128 cases with nonreassuring heart rate pattern. Cut off values were FIGO Score < 8 for the heart rate pattern and for fetal blood sampling during labor results of < 7.25 (preacidosis). The condition of the newborn was defined by the APGAR score with the cut off < 7 at 1 minute, while the biochemical status was evaluated by means of arterial blood sampling of the umbilical artery directly after birth using a pH of < 7.20 to verify acidosis. Predictive values of critically low SpO2 values (< 30%) for at least 10 minutes as well as corresponding sensitivities and specificities were calculated together with 95% confidence intervals to identify fetal distress or a depressed condition of the newborns. Of 128 fetuses included in this study 66 (52%) were born spontaneously, 23 (18%) were born by operative vaginal delivery and 39 (31%) by means of cesarean section. The high rate of cesarean section was due to cephalopelvic disproportion in 29 cases. Fetal outcome was evaluated with a clinical score: mean APGAR score value 8.5 SD +/- 1. The mean value of the pH in the umbilical artery was 7.23 +/- 0.04. During a SpO2 monitoring period of 18,381 minutes we analyzed a contact time of 63%. Comparing SpO2 values of < 30% with preacidosis in the fetal blood sampling, we found a positive predictive value of merely 0.17 (95% CI: 0.00-0.64). Of 9 preacidotic cases during delivery only 1 was indicated by a saturation value below 30% (sensitivity 0.11, 95% CI: 0.00-0.48). The specificity and negative predictive value were calculated as 0.83 (95% CI: 0.65-0.94) and 0.76 (95% CI: 0.58-0.89) respectively. Of eleven cases with acidosis in the blood of the umbilical cord artery, pH < 7.20, only 2 were indicated by a SpO2 values below 30%. Which is equivalent to a sensitivity of 0.18 (95% CI: 0.03-0.52). Results of a receiver operator curve analysis showed no substantial deviation from the diagonal. The area under the curve was 0.62, the 95% CI (0.47-0.76) indicating no significant discrimination. Three of 49 fetuses with SpO2 recording during the last 10 minutes were born in clinical depressed status (APGAR < 7). None was indicated by a SpO2 value below 30%.

CONCLUSION

Fetal distress and impaired condition of the newborn are not identified or predicted during routine application of SpO2 monitoring in the fetus during labor with adequate safety.

Intrapartum fetal monitoring: past, present, and future

The concept of intrapartum "monitoring" of the fetal heart rate by auscultation has been extant for almost 200 years and by electronic means for more than 30 years. This article explores historical aspects of fetal monitoring, the advent of electronic fetal monitoring and its controversies, and present and future research opportunities to enhance the reliability, validity, and efficacy of fetal monitoring.

Intermittent auscultation of the fetal heart rate: a review of general principles

Multiple randomized clinical trials have been unsuccessful in providing evidence of efficacy of electronic fetal monitoring; thus, there is renewed interest in intermittent auscultation during labor for women with low-risk pregnancies. Auscultation must be used with palpation or external or internal electronic monitoring of uterine contractions. Auscultation and palpation require education, experience, and competency validation at regular intervals. Institutional policies and standards of care are mandatory for intermittent auscultation. Concerns exist regarding the personnel costs for auscultation; however, these costs may ultimately be shown to be offset by significant benefits in improved outcomes and patient satisfaction.

Fetal heart rate monitoring: interpretation and collaborative management

Effective intrapartum fetal heart rate (FHR) monitoring requires ongoing collaboration among health care providers. Nurses, midwives, and physicians must have a shared understanding of 1) how FHR tracings are interpreted, 2) which FHR patterns are associated with actual or impending fetal acidemia, 3) when and within what time frame the physician or the midwife should be notified of variant FHR patterns, 4) how quickly physicians and midwives should respond when notified of variant patterns, and 5) the indications for and optimal timing of interventions such as operative delivery. This article reviews the literature on FHR monitoring and includes a discussion of the advantages and limitations of different monitoring modalities. An overview of those FHR patterns are associated with presumed fetal acidemia is presented, as well as sample multidisciplinary FHR monitoring guidelines and an exercise in intrapartum FHR pattern evaluation that can be used to initiate development of local FHR monitoring patterns.

A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns

OBJECTIVE

Recent developments permit the use of pulse oximetry to evaluate fetal oxygenation in labor. We tested the hypothesis that the addition of fetal pulse oximetry in the evaluation of abnormal fetal heart rate patterns in labor improves the accuracy of fetal assessment and allows safe reduction of cesarean deliveries performed because of nonreassuring fetal status.

STUDY DESIGN

A randomized, controlled trial was conducted concurrently in 9 centers. The patients had term pregnancies and were in active labor when abnormal fetal heart rate patterns developed. The patients were randomized to electronic fetal heart rate monitoring alone (control group) or to the combination of electronic fetal monitoring and continuous fetal pulse oximetry (study group). The primary outcome was a reduction in cesarean deliveries for nonreassuring fetal status as a measure of improved accuracy of assessment of fetal oxygenation.

RESULTS

A total of 1010 patients were randomized, 502 to the control group and 508 to the study group. There was a reduction of >50% in the number of cesarean deliveries performed because of nonreassuring fetal status in the study group (study, 4. 5%; vs. control, 10.2%; P =.007). However, there was no net difference in overall cesarean delivery rates (study, n = 147 [29%]; vs. control, 130 [26%]; P = .49) because of an increase in cesarean deliveries performed because of dystocia in the study group. In a blinded partogram analysis 89% of the study patients and 91% of the control patients who had a cesarean delivery because of dystocia met defined criteria for actual dystocia. There was no difference between the 2 groups in adverse maternal or neonatal outcomes. In terms of the operative intervention for nonreassuring fetal status, there was an improvement in both the sensitivity and the specificity for the study group compared with the control group for the end points of metabolic acidosis and need for resuscitation.

CONCLUSION

The study confirmed its primary hypothesis of a safe reduction in cesarean deliveries performed because of nonreassuring fetal status. However, the addition of fetal pulse oximetry did not result in an overall reduction in cesarean deliveries. The increase in cesarean deliveries because of dystocia in the study group did appear to result from a well-documented arrest of labor. Fetal pulse oximetry improved the obstetrician's ability to more appropriately intervene by cesarean or operative vaginal delivery for fetuses who were actually depressed and acidotic. The unexpected increase in operative delivery for dystocia in the study group is of concern and remains to be explained.

Cerebral infarction in the term newborn: clinical presentation and long-term outcome

OBJECTIVE

We evaluated the long-term neurodevelopmental outcome of cranial computed tomography (CT)-documented cerebral infarction in term neonates to ascertain factors that would help to predict the risk of subsequent neurodevelopmental sequelae in early childhood.

STUDY DESIGN

From 1983 to 1997, all surviving neonates from two level III neonatal intensive care units were prospectively identified and subsequently assessed in childhood. Clinical presentation was characterized by retrospective chart review and blinded re-reading of computed tomography (CT) scans. Perinatal events were compared with neurodevelopmental outcome.

RESULTS

Forty-six children were followed up for a mean of 42.1 months (range, 18-164 months). Neurodevelopmental outcome was normal in 15 and abnormal in 31. A single disability was present in 8, and multiple disabilities were present in 23. Cerebral palsy was present in 22 and cognitive impairment in 19. Abnormal findings on neurologic examination at discharge and seizures in the neonatal period were associated with the presence of one or more childhood disabilities. The site or laterality of the vascular distribution of the lesion on neonatal CT did not correlate with long-term outcome.

CONCLUSION

After cerebral infarction in the neonatal period, one third of term infants have normal long-term development. Neonatal seizure history and the findings on neurologic examination at discharge help in counseling parents about the possible long-term outcome of neonatal stroke.

Does asphyxia cause cerebral palsy?

The incidence of cerebral palsy is 1 per 1,000, whereas the proportion caused by perinatal asphyxia is only 8% to 10%. The purpose of this article is to review the relationship between asphyxia and cerebral palsy. Only a minority of cases, those involving severe pathological fetal academia, are consistently associated with neonatal encephalopathy and an increased risk of cerebral palsy.

Comparison of midwifery care to medical care in hospitals in the Quebec pilot projects study: clinical indicators. L'Equipe dEvaluation des Projets-Pilotes Sages-Femmes

The purpose of this study was to compare indicators of process and outcome of midwifery services provided in the Quebec pilot projects to those associated with standard hospital-based medical services. Women receiving each type of care (961 per group) were matched on the basis of socio-demographic characteristics and level of obstetrical risk. We found midwifery care to be associated with less obstetrical intervention and a reduction in selected indicators of maternal morbidity (caesarean section and severe perineal injury). For neonatal outcome indicators, midwifery care was associated with a mixture of benefits and risks: fewer babies with preterm birth and low birthweight, but a trend toward a higher stillbirth ratio and more frequent requirement for neonatal resuscitation. The study design does not permit to conclude that the associations were causal in nature. However, the high stillbirth rate observed in the group of women who were selected for midwife care raises concerns both regarding the appropriateness of the screening procedures for admission to such care and regarding the quality of care itself.

A comparison of the hemodynamic effects of paracervical block and epidural anesthesia for labor analgesia

BACKGROUND

Both paracervical block (PCB) and epidural analgesia are sometimes associated with hemodynamic effects potentially harmful to the well-being of the fetus. Our study was designed to test the hypothesis that PCB would have a more profound effect on maternal and fetal blood flow than epidural analgesia.

METHODS

Forty-four healthy primiparous parturients were randomized to receive either PCB (n=21) or epidural analgesia (n= 23) with 25 or 30 mg of bupivacaine, respectively, for labor analgesia. Maternal blood pressure and fetal heart rate were recorded. Blood flow was measured using a color Doppler device. The blood flow measurements consisted of assessment of the pulsatility indices (PI) of the right maternal femoral artery and the main branch of the uterine artery (placental side), the umbilical artery and the fetal middle cerebral artery. The measurements were performed before administration of analgesia and approximately 15-20 min later after the onset of analgesia.

RESULTS

Both methods provided in general good analgesia, but rescue medication was required more often after PCB. Epidural analgesia decreased maternal blood pressure more than PCB and the PI of maternal femoral artery decreased after onset of epidural analgesia, indicating epidural-induced vasodilation. The PI of the uterine artery increased after the onset of PCB, indicating vasoconstriction of this artery. No significant adverse effects or differences in the well-being of the newborn were observed, as indicated by similar Apgar scores and pH-status.

CONCLUSION

There were small differences in the effects of PCB and epidural analgesia on uteroplacental circulation as well as on maternal hemodynamics. PCB may have a vasoconstrictive effect on the uterine artery. This and the fact that the parturients required rescue analgesia more frequently after PCB than after epidural block speaks for the feasibility of the latter in obstetrics.

Fetal heart rate monitoring: is it salvageable?

Fetal heart rate monitoring was introduced in the 1960s. After a number of randomized controlled trials in the mid 1980s, doubt arose regarding the efficacy of fetal heart rate monitoring in improving fetal outcome. The potential reasons why fetal heart rate monitoring has not been shown to be efficacious are (1) use of an outcome measure that is not related to variant fetal heart rate monitoring patterns, (2) lack of standardized interpretation of fetal heart rate patterns, (3) disagreement regarding algorithms for intervention of specific fetal heart rate patterns, and (4) the inability to demonstrate the reliability, validity, and ability of fetal heart rate monitoring to allow timely intervention. A recent National Institutes of Health committee proposed detailed, quantitative, standardized definitions of fetal heart rate patterns, which can serve as a basis for determining whether fetal heart rate monitoring is reliable and valid. In this article we examine reasons why fetal heart rate monitoring did not live up to its original expectations and why the randomized controlled trials did not demonstrate efficacy, and we make suggestions for determining whether electronic fetal heart rate monitoring should be abandoned.

Intrapartum fetal pulse oximetry. Part I: Principles and technical issues

Fetal pulse oximetry has been advocated as a means of improving the specificity of cardioto-cography in intrapartum fetal surveillance. The objective of this article, the first of two reviewing the current literature on fetal pulse oximetry, is to discuss the principles of this new and evolving technology, its development, and the various factors that can affect its readings during fetal monitoring. It serves as a prelude to the second article, which profiles the clinical application of fetal pulse oximetry. Literature pertaining to this topic was selected from a MEDLINE search from 1965 through September 1999, with additional sources obtained through cross-referencing.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to explain the principles of fetal pulse oximetry, and describe the factors that affect the calibration of fetal pulse oximeters and the factors that affect the fetal pulse oximeter readings.

The PR interval-fetal heart rate relationship during repetitive umbilical cord occlusions in immature fetal sheep

OBJECTIVE

To evaluate the relationship of the PR interval and fetal heart rate during repetitive umbilical cord occlusions in immature sheep fetuses.

STUDY DESIGN

In seven chronically cannulated immature sheep fetuses [gestational age 90.6 days (mean)], we analyzed continuous fetal electrocardiogram recordings during repetitive cord occlusions for 2 out of every 5 min until fetal mean arterial pressure dropped to 50% of baseline value. PR interval-fetal heart rate correlation coefficients (Pearson) was measured on consecutive blocks of 2.5 min. R-values of the baseline and the repetitive occlusion period were compared by Fisher's exact test.

RESULTS

Repetitive cord occlusions resulted in acidosis and hypotension. Two fetuses died at the end of the repetitive occlusion period. Four out of seven fetuses showed a significant change from a negative relationship between the PR interval and fetal heart rate during baseline to a predominantly positive relationship during the repetitive occlusion period.

CONCLUSION

In immature fetal sheep, a change from a negative relationship between the PR interval and fetal heart rate to a predominantly positive relationship between the PR interval and fetal heart rate was observed in four out of seven fetuses following the initiation of repetitive umbilical cord occlusions.

Fetal distress

The term 'fetal distress' should be replaced by 'suspected fetal compromise' because the diagnosis of 'fetal distress' is often unproven. Cardiotocography remains the cornerstone of making the diagnosis, but as a test it is renowned for its high sensitivity and low specificity. It has reduced intrapartum fetal mortality but not long-term neonatal morbidity or the incidence of cerebral palsy. There is no doubt that when obvious signs of fetal compromise, such as late decelerations in the presence of intrauterine growth retardation and oligohydramnios, are present, the diagnosis of fetal compromise is relatively simple. Often, however, the subtle signs of fetal compromise are missed; these are a change in the grade of meconium in the amniotic fluid, a rising base-line fetal heart rate, the absence of accelerations, the presence of 'atypical' variable decelerations or a combination of the above. To date, there is no test available to replace the cardiotocograph, although fetal pulse oximetry is the most promising adjunctive test. Above all, no test result obtained in isolation must detract from the whole clinical picture.

Electronic fetal heart rate monitoring: early neonatal outcomes associated with normal rate, fetal stress, and fetal distress

OBJECTIVE

The purpose of this study was to test the ability of a clearly defined classification system for electronic fetal heart rate monitoring to predict early neonatal outcome.

STUDY DESIGN

All labors of women with singleton pregnancies > or = 32 weeks' gestation electronically monitored at 2 institutions were examined. Tracings in the final hour before delivery were defined as normal, fetal stress, or fetal distress. After delivery, Apgar scores, cord blood gas values, and admission to the neonatal intensive care unit were examined as measures of early neonatal outcome.

RESULTS

Among the 898 patients who qualified for study, 627 (70%) had tracings classified as normal, 263 (29%) had tracings classified as fetal stress, and 8 (1%) had tracings classified as fetal distress. There was a significant worsening of neonatal outcome across these 3 groups with regard to depressed Apgar scores 1 minute (5.1%, 18.3%, and 75.0%; P <.05), depressed Apgar scores at 5 minutes (1.0%, 3.8%, and 37.5%; P <.05), and admission to the neonatal intensive care unit (5.6%, 10.6%, and 37.5%; P <.05). There was also a progressive worsening of cord blood pH (7.27 +/- 0.06, 7.21 +/- 0.08, and 7.06 +/- 0.14; P <.05), a progressive increase in PCO (2) (53.39 +/- 8.34 mm Hg, 58.51 +/- 10.55 mm Hg, and 78.31 +/- 20.35 mm Hg; P <.05), and a progressive decline in base excess (-3.18 +/- 2.02 mEq/L, -5. 11 +/- 3.11 mEq/L, and -9.07 +/- 4.59 mEq/L; P <.05).

CONCLUSION

This simple classification system for interpreting fetal heart rate tracings accurately predicts normal outcomes for fetuses as well discriminating fetuses in true distress. Further, it identifies an intermediate group of fetuses with a condition labeled fetal stress who might benefit from additional evaluation and possibly from expeditious delivery.

Continuous electronic heart rate monitoring for fetal assessment during labor

BACKGROUND

Electronic fetal monitoring (EFM) has been widely adopted. There is debate about its overall effectiveness as well as the relative merits of routine application versus use for high-risk pregnancies only.

OBJECTIVES

The objective of this review was to assess the effects of routine continuous electronic fetal monitoring during labour compared with intermittent auscultation.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register, Medline (1966 to 1994), and reference list of relevant articles. We also contacted experts in the field.

SELECTION CRITERIA

Randomised trials comparing routine continuous electronic fetal monitoring with intermittent auscultation.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer, and their accuracy was confirmed independently by a second person. A single reviewer assessed study quality based on criteria developed by others for randomised controlled trials. Data reported from similar studies were used to calculate a combined risk estimate for each of eight outcomes.

MAIN RESULTS

Nine studies involving 18,561 women and their 18,695 infants were included. The trials were of variable quality. A statistically significant decrease was associated with routine continuous EFM for neonatal seizures (relative risk (RR) = 0. 51, confidence interval (CI) = 0.32,0.82). The protective effect for neonatal seizures was only evident in studies with high-quality scores. No significant differences were observed in 1-minute Apgar scores below 4, 1-minute Apgar scores below 7, rate of admissions to neonatal intensive care units, and perinatal death. An increase associated with the use of EFM was observed in the rate of cesarean delivery (RR = 1.41, CI = 1.23,1.61) and operative vaginal delivery (RR = 1.20, CI = 1.11,1.30).

REVIEWER'S CONCLUSIONS

The only clinically significant benefit from the use of routine continuous EFM was in the reduction of neonatal seizures. In view of the increase in cesarean and operative vaginal deliveries, the long-term benefit of this reduction must be evaluated in the decision reached jointly by the pregnant woman and her clinician to use continuous EFM or intermittent auscultation during labor.

Placental oxygen transfer and intrauterine resuscitation: a survey of knowledge in maternity care professionals

We surveyed 99 maternity care professionals (obstetricians, midwives and anaesthetists in equal numbers) to assess their knowledge of potential treatments during acute intrapartum fetal hypoxia, including maternal oxygen administration. Knowledge of adult arterial oxygen saturation was satisfactory, but few of those surveyed gave a correct figure for fetal oxygenation in terms of umbilical vein oxygen saturation. Only 58% said that maternal oxygen inhalation would affect fetal oxygenation, and 76% of those giving a figure underestimated the potential extent of the increase. Other aspects of intrauterine resuscitation were also not identified. Out of three further factors besides maternal oxygen administration which are commonly considered, 76% suggested none or one, and only 24% noted two or all three. Acute fetal hypoxia during labour and delivery may be amenable to correction by improving oxygen supply to the placenta. We identified deficits in the underlying knowledge of these processes among maternity care professionals. Without this knowledge, correctable causes of fetal hypoxia may go untreated.

Scalp blood gas analysis

The use of fetal blood sampling has been advocated widely to improve the specificity of fetal heart rate monitoring, but it remains a clinically unpopular procedure. This article considers its physiologic rationale and evidence base. It includes descriptions of the technique with suggestions for improved clinical interpretation and discusses the efficacy of fetal blood sampling with some consideration of possible alternatives.

Intrapartum fetal heart rate monitoring

Intrapartum fetal heart rate monitoring is commonly used to evaluate fetal status in labor, despite a lack of convincing randomized studies to support its use. The National Institutes of Health have helped standardize fetal heart rate monitoring terminology with their 1997 task force report, which will aid clinicians and scientists in their goal of providing quality care and research. The American College of Obstetricians and Gynecologists has recommended the term nonreassuring fetal status for electronic fetal monitor patterns that are not normal; however, Vanderbilt continues to use the terms fetal stress and fetal distress, using specific criteria for each. The approximately 30% of fetal heart rate tracings labeled as fetal stress (or nonreassuring fetal status) can be evaluated further by the use of fetal pulse oximetry, a new technology currently under evaluation in this country.

Neonatal asphyxia, definitive markers and hearing loss

A study of 56 severely asphyxiated infants (8 hearing impaired and 46 normally hearing) was designed to identify specific markers associated with asphyxia which could be related to hearing loss. Sixteen variables, including such items as: one- and five-minute Apgar scores, muscle tone, use of a ventilator, prolonged stay in the NICU, hypoxic-ischemic encephalopathy (HIE), other organ damage, and intra-uterine growth retardation (IUGR) were considered. Results suggested four factors related to asphyxia which are often found in the presence of hearing loss, but none of these was considered a definitive marker or predictor of such a disability. A combination of HIE, seizures, associated organ damage and IUGR should be considered a strong marker for the probability of a sensorineural hearing loss.

Differences in the valuation of birth outcomes among pregnant women, mothers, and obstetricians

BACKGROUND

Decisions are usually based on the perceived merits of alternative approaches. This process can be quantified by combining the probabilities of expected outcomes with their desirability. We studied differences in the valuation of birth outcomes among pregnant women, mothers, and obstetricians, and assessed how these would affect a particular obstetric decision.

METHODS

In a study conducted at Leiden Hospital, Leiden, The Netherlands, 12 obstetricians, 15 pregnant women, and 15 mothers participated in a standard reference gamble to determine the value of 12 different outcomes: 3 types of birth combined with 4 states of infant outcome. These were then applied to an obstetric decision tree based on the Dublin trial of intermittent auscultation versus electronic intrapartum fetal heart rate monitoring.

RESULTS

Contrary to obstetricians, women valued permanent neurologic handicap significantly higher than neonatal death (p < 0.01). Women expressed no overriding preferences for the type of birth, whereas obstetricians were clearly antipathetic to cesarean section. Within-group consistency was significantly higher for pregnant women and mothers than for obstetricians (p < 0.0001). However, application of the measured values to the obstetric decision tree merely led to marginal changes in overall expected value of the decision alternatives.

CONCLUSIONS

Values attached to birth processes and outcomes differ significantly between (expectant) mothers and doctors. These differences should be recognized and respected in obstetric decision making.

Continuous electronic fetal monitoring: contradictions between practice and research

The reliability, validity, and efficacy of electronic fetal monitoring (EFM) remain matters of controversy. In fact, several professional organizations, including the American College of Obstetricians and Gynecologists, have endorsed the use of intermittent auscultation for low-risk pregnant women. Nevertheless, in 1996, 83% of laboring women in the United States are monitored electronically. Nurses should encourage healthy, low-risk pregnant women to weigh carefully decisions about the use of EFM.

Management of fetal distress

Since its introduction more than 20 years ago, continuous electronic FHR monitoring has become the standard in most modern obstetric units. Practitioners well versed in FHR pattern interpretation do not question the value of fetal monitoring. Not only does this modality detect hypoxia early in its evolution, but also it allows the opportunity to understand the physiology of the hypoxia and to intervene if necessary. Although nonrandomized studies demonstrate an improvement in the perinatal death rate with continuous monitoring, most randomized studies have failed to confirm this observation. Continuous fetal monitoring has been associated in several studies with an increase in the CS rate; however, concomitant changes in obstetric practice have also raised the incidence of CS, making the interpretation of to what degree fetal monitoring is responsible for this increase difficult. Other than this association with an increased CS rate, fetal monitoring seems to present few risks. A thorough understanding of basic fetal heart abnormalities is crucial to prevent unnecessary intervention; however, although quite sensitive, FHR monitoring remains nonspecific in predicting fetal metabolic acidosis. Fetal pulse oximetry is a recent development still undergoing investigation. The ability to measure fetal oxygen saturation during labor adds critical information about fetal status and refines the interpretation of abnormal FHR patterns. If approved by the US Food and Drug Administration, it has the potential to affect dramatically the practice of obstetrics.

Problems in the detection of intrapartum fetal asphyxia with intermittent auscultation

We present 4 cases of severe intrapartum fetal asphyxia occurring during spontaneous unaugmented labours at term in low-risk women. In each case the baseline heart rate was completely normal, and the only indication of asphyxia was markedly decreased variability detected with electronic fetal heart rate monitoring. Correct action was taken in 3 cases that probably prevented fetal death or reduced neonatal morbidity. In no case would intermittent auscultation have been able to identify the compromised fetus.

Intrapartum fetal oxygen saturation monitoring in a busy labour ward

OBJECTIVE

To measure the ease of use of a fetal pulse oximeter in a busy labour ward.

DESIGN

Descriptive study in the Labour Ward, National University Hospital, Singapore, involving 145 labouring women with singleton pregnancies, and fetuses in cephalic presentation, with cervical dilatation >2 cm and amniotic membranes ruptured.

RESULTS

Placement was comfortable. Oxygen saturation (SpO2) readings were obtained in 127 women (87.5%). Adequate readings were obtained a median of 69% of the time the transducer was in situ. SpO2 values in the last 10 min prior to delivery correlated poorly with parameters of neonatal outcome.

CONCLUSION

The Nellcor N-400 fetal pulse oximeter and FS14 fetal sensor is a feasible method of intrapartum fetal monitoring in a busy labour ward and is acceptable to labouring women.

The prediction of fetal acidosis by means of intrapartum fetal pulse oximetry

OBJECTIVES

The study's objectives were to verify a threshold value for fetal arterial oxygen saturation as the critical boundary for fetal compromise during labor and to investigate a method of predicting acidosis caused by hypoxemia.

STUDY DESIGN

In a multicenter study involving 3 German obstetric centers, a total of 400 deliveries were monitored by fetal pulse oximetry (Nellcor-Puritan-Bennett Model N-400 Oxygen Saturation Monitor and FS-14 Sensor; Nellcor, Inc, Pleasanton, Calif). The durations of low (</=30%), medium (31%-60%), and high (>60%) fetal arterial oxygen saturations during the measurement were compared between neonates with a pH <7.15 versus >/=7.15 and a base excess <-12 mmol/L versus >-12 mmol/L in the umbilical artery post partum and in neonates with an Apgar score <7 versus >/=7 by Mann-Whitney U test. In 121 of the pulse oximetry measurements the durations of low, medium, and high fetal arterial oxygen saturations were measured from one fetal scalp blood sampling to the next and correlated with the change of scalp blood pH between samplings. Multiple regression analysis was performed to estimate the expected change of pH between 2 fetal scalp blood samplings, and receiver operating characteristic analysis was done to define a minimum duration of low fetal arterial oxygen saturation values to exclude or predict a significant decline of pH.

RESULTS

Neonates with a 1-minute Apgar score <7 differed from those with 1-minute Apgar score >/=7 significantly in the duration of low fetal arterial oxygen saturation but not in the durations of medium and high fetal arterial oxygen saturations. The duration of low fetal arterial oxygen saturation had been significantly longer in children with pH <7.15 or base excess <-12 mmol/L in the umbilical artery compared with those with a pH >/=7.15 or base excess >/=-12 mmol/L. The duration of high fetal arterial oxygen saturation was significantly shorter for children with a pH <7.15 or base excess <12 mmol/L than for those with a pH >/=7.15 or base excess >/=12 mmol/L. There was no difference in the groups with respect to the duration of medium fetal arterial oxygen saturation values. The duration of low fetal arterial oxygen saturation proved to be the best predictor of a decline of scalp pH between 2 fetal scalp blood samples. The pH declined significantly with a longer duration of low fetal arterial oxygen saturation (0.02 per 10 minutes). No decrease of pH by more than 0.05 was observed unless fetal arterial oxygen saturation had remained at </=30% for >/=10 minutes.

CONCLUSION

An arterial oxygen saturation of 30% was confirmed as the critical boundary for fetal compromise during labor. The development of acidosis seems to be predictable by the duration of hypoxemia, as indicated by fetal arterial oxygen saturation </=30%.

Fetal heart rate patterns in postasphyxiated fetal lambs with brain damage

OBJECTIVE

We previously showed that in asphyxiated fetal lambs the duration of hypotension correlated well with the severity of histologic damage to the brain, whereas the duration of bradycardia did not. This study compares fetal heart rate patterns with the degree of histologic damage to the brain.

STUDY DESIGN

Twelve chronically instrumented near-term fetal lambs were subjected to asphyxia by umbilical cord occlusion until fetal arterial pH was <6. 9 and base excess was <-20 mEq/L. An additional 4 fetuses served as sham-asphyxia controls. Fetal heart rate (from electrocardiogram), arterial blood pressure, fetal breathing movements, and electrocorticogram were continuously monitored before, during, and for 72 hours after asphyxia. Fetal brain histologic features were categorized as mild (group 1, n = 5), moderate (group 2, n = 4), and severe (group 3, n = 3). Long-term fetal heart rate variability expressed as amplitude range was assessed visually every 5 minutes from 30 minutes before asphyxia until 2 hours of recovery and at 6, 12, 24, 48, and 72 hours of recovery.

RESULTS

Long-term fetal heart rate variability amplitude decreased from 32 +/- 17 beats/min (mean +/- SEM) preocclusion to 4 +/- 13 beats/min at the end of occlusion (P <.001) without significant differences among the 3 groups. During 10 to 45 minutes of recovery, the long-term variability of group 1 was significantly greater than that of groups 2 and 3. At 24 to 72 hours of recovery, the long-term variability of groups 1 and 2 was significantly higher than that of group 3, which was almost 0. The "checkmark" and sinusoidal fetal heart rate patterns were observed during the recovery period in groups 2 and 3.

CONCLUSIONS

Decreased long-term fetal heart rate variability and the "checkmark" and sinusoidal fetal heart rate patterns were indicators of the severity of asphyxial histologic damage in the fetal brain.

Intrapartum fetal oxygen saturation monitoring in congenital fetal heart block

Conventional intrapartum electronic fetal heart rate monitoring is not informative in certain fetal conditions because the electronically-monitored fetal heart rate pattern is uninterpretable in terms of reflecting fetal normoxia. Such fetal conditions include various cardiac dysrrhythmias and some central nervous system abnormalities. Difficulties with intrapartum fetal welfare surveillance in such conditions often lead to operative delivery as a precautionary measure. We report 2 cases of intrapartum fetal oxygen saturation monitoring in the presence of congenital complete heart block (CCHB), using the Nellcor N400/FS14 oxygen saturation monitoring system. Mean intrapartum fetal oxygen saturation (FSpO2) was 32% (SEM +/- 1%) in the first case and 48% (SEM +/- 0.3%) in the second case. In both cases, vaginal delivery of otherwise healthy infants was achieved. Fetal pulse oximetry is a promising new technique which directly measures fetal oxygenation without reference to fetal heart rate patterns. It may assist in the intrapartum fetal welfare assessment in conditions such as complete heart block, thereby helping to avoid otherwise unnecessary operative delivery.

The incidence of abnormal findings from intrapartum cardiotocogram monitoring in term and preterm labours

A retrospective analysis of 514 consecutive labours delivering 530 babies over a period of 18 months was conducted by a high-risk pregnancy team in a tertiary teaching unit to compare the incidence of abnormal findings from intrapartum monitoring between labours occurring before and at or after 34 weeks' gestation. Those delivered by elective Caesarean section, or Caesarean section at the onset of labour because of contraindications to labour and vaginal delivery, and those with congenitally malformed fetuses were excluded. Tracings were scored using the FIGO 1987 guidelines. Seventy-four labours and 83 babies delivered before 34 weeks, and 440 labours and 447 babies delivered after 34 weeks in the study. There was a slightly higher incidence of suspicious CTG tracings (33.7% versus 19.6%, OR 2.66, 95% CI 1.6-4.4) in the preterm group, due mainly to decreased baseline variability (p<0.001, OR 3.57, 95% CI 1.8-6.9), but the incidence of other pathological patterns did not differ. Using the same set of criteria for interpretation, there was a higher incidence of abnormalities from continuous cardiotocogram monitoring in the preterm group compared to term labours, but the intervention rate for fetal distress was not significantly increased. Appropriate interpretative criteria for intrapartum monitoring of preterm labours should be devised.

Obstetric risk factors for periventricular leukomalacia among preterm infants

OBJECTIVE

To evaluate the obstetric antecedents of cystic periventricular leukomalacia and transient echodense periventricular lesions among preterm infants.

DESIGN

A cohort study of preterm singleton infants born between 25 and 33 weeks gestation.

SETTING

Pavia, Italy.

POPULATION

Three hundred and forty-nine infants admitted to a Division of Neonatal Intensive Care who were screened for periventricular leukomalacia.

METHOD

The obstetric factors in infants with either cystic periventricular leukomalacia or transient echodense periventricular lesions were compared to those in infants with negative cranial ultrasonographic findings. Stepwise multiple logistic regression analysis was used to evaluate the association between risk factors and outcomes adjusting for confounders.

RESULTS

The prevalence of cystic periventricular leukomalacia and transient echodense lesions was 5.7% (20/349) and 14% (49/349), respectively. The main risk factors for cystic leukomalacia were first trimester haemorrhage (OR 4.49; 95% CI 1.63-12.39), maternal urinary tract infection on admission (OR 5.71; 95% CI 1.91-17.07), and neonatal acidosis (pH < 7.2) at birth (OR 5.97; 95% CI 1.93-18.52). Meconium-stained amniotic fluid (OR 3.95; 95% CI 1.42-10.98) and long term (> 72 hours) ritodrine tocolysis (OR 2.54; 95% CI 1.28-5.05) were associated with an increased risk of echodense lesions. The likelihood of overall leukomalacia (cystic plus echodense periventricular lesions) was increased among cases with meconium-stained amniotic fluid (OR 4.06; 95% CI 1.65-10.0), long-term ritodrine tocolysis (OR 2.56; 95% CI 1.38-4.72), maternal infection (OR 1.73; 95% CI 1.0-3.0), and acidosis at birth (OR 1.98; 95% CI 1.0-3.98).

CONCLUSIONS

This study confirms that maternal infection, acidosis at birth, and meconium-stained amniotic fluid increase the risk of periventricular leukomalacia in preterm infants. Long-term ritodrine use seems to increase the risk for transient echodense lesions.

Electronic fetal monitoring: a brief summary of its development, problems and prospects

Electronic fetal monitoring (EFM) was introduced into clinical practice 30 years ago and spread very rapidly in most developed countries. The early optimism that EFM would lead to a marked reduction in fetal neurological injury has not been realized; however, it is now recognized that most such damage is unrelated to perinatal events. Clinical trials have shown that although EFM does reduce the incidence of intrapartum asphyxia, its use is also associated with an increase in cesarean sections. Abnormal fetal heart rate (FHR) patterns are poor predictors of fetal depression at birth when used without additional confirmatory information. An additional problem has been inconsistency in the interpretation of EFM tracings even among experts. This has reduced the clinical effectiveness of EFM and has also contributed to an increase in litigation in cases with adverse neonatal outcomes. Despite these shortcomings EFM continues to be used extensively on most obstetrical services, suggesting that obstetrical physicians and nurses find the technique helpful and will continue to use it until a better alternative comes along. The combination of relevant clinical data with EFM by means of intelligen computer systems may improve both the consistency and predictive value of intrapartum fetal assessment in the future.

Multicenter study on the clinical value of fetal pulse oximetry. II. Compared predictive values of pulse oximetry and fetal blood analysis. The French Study Group on Fetal Pulse Oximetry

OBJECTIVE

Our purpose was to compare the predictive value of intrapartum fetal pulse oximetry with that of fetal blood analysis for an abnormal neonatal outcome in case of an abnormal fetal heart rate.

STUDY DESIGN

A prospective multicenter observational study was conducted from June 1994 to November 1995. Fetal oxygen saturation was continuously recorded with a Nellcor N-400 fetal pulse oximeter in case of an abnormal fetal heart rate during labor. Simultaneous readings of fetal oxygen saturation and fetal blood analysis obtained before birth (i.e., either at full dilatation or before cesarean section when indicated) were compared with the neonatal status. The criteria for an abnormal neonatal outcome were (1) an umbilical arterial blood pH < or = 7.15 and (2) a combined variable including 5-minute Apgar score < or = 7, umbilical arterial pH < or = 7.15, secondary respiratory distress, transfer in a neonatal care unit, or neonatal death.

RESULTS

At a 7.20 threshold for fetal scalp pH and 30% for fetal oxygen saturation (i.e., the 10th percentile in the study population), the predictive value of fetal pulse oximetry was similar to that of fetal blood analysis for an arterial umbilical pH < or = 7.15 and for an abnormal neonatal outcome (positive predictive value 56% vs 55%, negative predictive value 81% vs 82%, sensitivity 29% vs 35%, and specificity 93% vs 91%, respectively). The receiver-operator characteristic curve showed similar performance of either technique for cutoff values < or = 7.20 for fetal blood pH and < or = 30% for fetal oxygen saturation, whereas fetal pulse oximetry became superior at higher thresholds.

CONCLUSION

The predictive value of intrapartum fetal pulse oximetry can be favorably compared with that of fetal blood analysis. Randomized controlled management trials can now be performed to assess potential clinical benefits of this new tool.

Intermittent auscultation for the intrapartum assessment of fetal well-being in Western Australia

In May 1995, in response to a decision of the Perinatal and Infant Mortality Committee of Western Australia, a survey of Western Australian hospitals was performed to ascertain what policies were in use for the monitoring of the fetal heart rate in labour and what proportion of these hospitals had access to electronic monitoring by cardiotocography. A response was received from 96% of the surveyed hospitals. More than half the births in this State (13,950 of 25,238) were monitored in labour using intermittent auscultation as the primary test; 7.5% of Western Australian births each year occurred in hospitals in which electronic monitoring was not available. Fewer than 50% of hospitals had written protocols describing the method of auscultation of the fetal heart during labour, the indications to contact a doctor or the management of fetal distress. The protocols which did exist displayed considerable variation in the recommended frequency of intermittent auscultation. The lack of standard practice in this field probably results from uncertainties in the literature. Intermittent auscultation has not been subjected to rigorous scientific evaluation as a screening tool and guidelines documenting ideal auscultatory practices need to balance the precision of electronic monitoring and freedom from intervention. Based on this compromise and existing evidence, a protocol for intermittent auscultation in normal labour is proposed.

Current status of the multicenter randomized clinical trial on fetal oxygen saturation monitoring in the United States

Current clinical methods of intrapartum fetal assessment are sensitive but poorly specific in detecting fetal compromise during labor. These limitations have substantially contributed to the escalating cesarean section rate which occurred in the US during the last several decades. Experimental and clinical research efforts directed towards application of the oxygen saturation monitor (pulse oximeter) to intrapartum fetal assessment have produced encouraging results. If this new method of fetal assessment is to enter the clinical arena, safety and efficacy issues must first be properly evaluated via randomized clinical trials. The purpose of this report is to describe the design of a multicenter randomized clinical trial of intrapartum fetal oxygen saturation monitoring recently begun in the US. Specific aspects of the trial, including purpose, study design, sample size estimates, control and test groups, inclusion and exclusion criteria, fetal heart rate classification, definition of normal fetal arterial oxygen saturation (SpO2), clinical management protocol, and assessment of maternal-fetal outcomes will be addressed.