Predictors of intrapartum fetal distress: the role of electronic fetal monitoring. Report of the National Institute of Child Health and Human Development Consensus Development Task Force

Investigating gene methylation signatures for fetal intolerance prediction

Pregnancy is a complicated and long procedure during one or more offspring development inside a woman. A short period of oxygen shortage after birth is quite normal for most babies and does not threaten their health. However, if babies have to suffer from a long period of oxygen shortage, then this condition is an indication of pathological fetal intolerance, which probably causes their death. The identification of the pathological fetal intolerance from the physical oxygen shortage is one of the important clinical problems in obstetrics for a long time. The clinical syndromes typically manifest five symptoms that indicate that the baby may suffer from fetal intolerance. At present, liquid biopsy combined with high-throughput sequencing or mass spectrum techniques provides a quick approach to detect real-time alteration in the peripheral blood at multiple levels with the rapid development of molecule sequencing technologies. Gene methylation is functionally correlated with gene expression; thus, the combination of gene methylation and expression information would help in screening out the key regulators for the pathogenesis of fetal intolerance. We combined gene methylation and expression features together and screened out the optimal features, including gene expression or methylation signatures, for fetal intolerance prediction for the first time. In addition, we applied various computational methods to construct a comprehensive computational pipeline to identify the potential biomarkers for fetal intolerance dependent on the liquid biopsy samples. We set up qualitative and quantitative computational models for the prediction for fetal intolerance during pregnancy. Moreover, we provided a new prospective for the detailed pathological mechanism of fetal intolerance. This work can provide a solid foundation for further experimental research and contribute to the application of liquid biopsy in antenatal care.

Intrapartum cardiotocograph monitoring and perinatal outcomes for women at risk: Literature review

PROBLEM

Caesarean section rates have risen in high-income countries. One of the potential drivers for this is the widespread use of CTG monitoring.

BACKGROUND

Intrapartum cardiotocograph monitoring is considered to be indicated for women at risk for poor perinatal outcome.

AIM

This systematic literature review with meta-analysis examined randomised controlled trials and non-experimental research to determine whether cardiotocograph monitoring rather than intermittent auscultation during labour was associated with changes in perinatal mortality or cerebral palsy rates for high-risk women.

METHODS

A systematic search for research published up to 2019 was conducted using PubMed, CINAHL, Cochrane, and Web of Science databases. Non-experimental and randomised controlled trial research in populations of women at risk which compared intrapartum cardiotocography with intermittent auscultation and reported on stillbirth, neonatal mortality, perinatal mortality and/or cerebral palsy were included. Relative risks were calculated from extracted data, and meta-analysis of randomised controlled trials was undertaken.

FINDINGS

Nine randomised controlled trials and 26 non-experimental studies were included. Meta-analysis of pooled data from RCTs in mixed- and high-risk populations found no statistically significant differences in perinatal mortality rates. The majority of non-experimental research was at critical risk of bias and should not be relied on to inform practice. Cardiotocograph monitoring during preterm labour was associated with a higher incidence of cerebral palsy.

DISCUSSION

Research evidence failed to demonstrate perinatal benefits from intrapartum cardiotocograph monitoring for women at risk for poor perinatal outcome.

CONCLUSION

There is an urgent need for well-designed research to consider whether intrapartum cardiotocograph monitoring provides benefits.

Computerised analysis of antepartum foetal heart parameters: New reference ranges

We selected 4012 cCTG records (one trace for each patient) performed in healthy pregnancies from 30th to 42nd gestational week using foetal heart rate (FHR), short-term variability (STV), long-term irregularity (LTI), Delta, approximate entropy (ApEn), spectral components as low frequency (LF), median frequency (MF), high frequency (HF) and LF/(HF + MF) ratio were analysed. Reference nomograms were created and sensitivity and specificity for the prediction of foetal compromise were calculated which were 90% and 89%, respectively. Changes of cCTG parameters according to gestational week were evaluated: FHR (r = -.65) and LF (r = -.87) showed a statistically significant reduction (p < .05) with gestational age. STV (r = .59), LTI (r = .69), Delta (r = .67), and MF (r = .88) showed a statistically significant increase (p < .05) with gestational age. In contrast, for ApEn (r = -.098), HF (r = .14) and LF/(HF + MF) ratio (r = -.47) a non-statistically significant change was found (p > .05). The identification of reference ranges for cCTG indexes in according to gestational age could provide a more objective examination of cCTG trace.

Perpetuating Myths, Fables, and Fairy Tales: A Half Century of Electronic Fetal Monitoring

Electronic fetal monitoring (EFM) entered clinical medical practice at the same time bioethics became reality. Bioethics changed the medical ethics landscape by replacing the traditional Hippocratic benign paternalism with patient autonomy, informed consent, beneficence, and nonmaleficence. But EFM use represents the polar opposite of bioethics' revered principles-it has been documented for half a century to be completely ineffectual, used without informed consent, and harmful to mothers and newborns alike. Despite EFM's ethical misuse, there has been no outcry from the bioethical world. Why? This article answers that question, discussing EFM's history and the reasons it was issued an ethics pass. And it explores the reason that even today mothers are still treated with blatant medical paternalism, deprived of autonomy and informed consent, and subjected to real medical risks under the guise that EFM is an essential safety device when in fact it is used almost solely to protect physicians and hospitals from cerebral palsy lawsuits.

Utility of intraoperative fetal heart rate monitoring for cerebral arteriovenous malformation surgery during pregnancy

We report two methods of intraoperative fetal heart rate (FHR) monitoring in cases of cerebral arteriovenous malformation surgery during pregnancy. In one case in her third trimester, cardiotocography was used. In another case in her second trimester, ultrasound sonography was used, with a transesophageal echo probe attached to her lower abdomen. Especially, the transesophageal echo probe was useful because of the advantages of being flexible and easy to attach to the mother's lower abdomen comparing with the usual doppler ultrasound probe. In both cases, the surgery was successfully performed and FHR was monitored safely and stably. The use of intraoperative FHR monitoring provides information about the influence of induced maternal hypotension and unexpected bleeding on fetus during surgery. These monitoring techniques would be especially emphasized in cerebrovascular surgery for the safe management of both mother and fetus.

Reliability of admission cardiotocography for intrapartum monitoring in low resource setting

Background

To evaluate the role of admission cardiotocography in intrapartum patients in detecting fetal hypoxia already present and to correlate the results of admission cardiotocography with perinatal outcome.

Materials and Methods:

It was a cross-sectional study conducted in the Labor and Maternity ward during the period 2007-2009. The study included 176 pregnant women (both high risk and low risk), admitted to the emergency department or through the outpatient department with period of gestation ≥36 weeks, in first stage of labor with fetus in cephalic presentation. All of them were subjected to an admission test, a 20 min recording of fetal heart rate and uterine contractions on cardiotocograph machine at the time of admission.

Results:

The results of the admission test were ‘reactive’ in 82.38%, ‘equivocal’ in 10.22%, and ‘ominous’ in 7.38% women. Women with the reactive admission test had low risk of intrapartum fetal distress (6.9%) as compared to 39.9% in the equivocal and 84.6% in the ominous group (P<0.001). Incidence of moderate to thick meconium stained liqor were more in ominous (61.5%) and equivocal group (33.3%) in compared to reactive group (4.8%) (P<0.001). Incidence of NICU admission was also significantly high (62%) in babies delivered from mother with ominous test group compared to those with equivocal (28%) and reactive test (3.45%) group babies. Neonatal mortality was also seen in babies born to mothers with equivocal (5.5%) and ominous (7.6%) admission test groups. Operative delivery for fetal distress was required in only 5.5% (8 of 145) woman of the reactive group, in 27.8% (5 of 18) woman of the equivocal group and in 84.6% (11 of 13) women of the ominous group.

Conclusion:

The admission cardiotocography is a simple non-invasive test that can serve as screening tool to detect fetal distress already present or likely to develop and prevent unnecessary delay in intervention. The test has high specificity and can help in ‘triaging’ fetuses in obstetric wards of developing countries with a heavy workload and limited resources.

Quality of intrapartum cardiotocography in twin deliveries

OBJECTIVE

Intrapartum fetal heart rate (FHR) recordings in twins were compared for fetal signal loss during both stages of labor to assess the quality of these recordings by the method that had been used: external ultrasound or directly via a scalp electrode.

STUDY DESIGN

Analysis of recordings collected between January 1, 1994, and January 1, 2002, from consecutive twin deliveries at the Vrije Universiteit Medical Center in Amsterdam. One hundred seventy-two twins that delivered via the vaginal route were included in the study. FHR recordings had a duration of at least 1 hour before the birth of the second twin. Subdivision took place on the basis of the recording technique, ie, ultrasound or scalp electrode. FHR data was obtained with HP-M1350 cardiotocographs. The status (pen on, pen off, maternal signal) and the mode of the signals were acquired. The duration of pen lifts and maternal signals was divided by the total duration of the recording. Statistical analyses were performed with the Mann-Whitney U test and the Wilcoxon signed ranks test.

RESULTS

Recordings obtained via ultrasound demonstrated significantly more fetal signal loss than those obtained via the direct mode, particularly in the second stage. Approximately 26% to 33% of first stage and 41% to 63% of second stage ultrasound intrapartum FHR recordings in twins exceeded the International Federation of Gynecology and Obstetrics (FIGO) criteria for fetal signal loss.

CONCLUSION

Intrapartum FHR monitoring via ultrasound provides far poorer quality FHR signals than the direct mode. The direct mode deserves a more prominent position in fetal surveillance than it currently has.

The quality of intrapartum fetal heart rate monitoring

OBJECTIVE

To determine the quality of fetal heart rate (FHR) recordings during the first and second stage of labor by quantifying the amount of fetal signal loss in relation to the method of monitoring: external ultrasound or directly via a scalp electrode.

STUDY DESIGN

Analysis of 239 intrapartum recordings stored between 1 January 2001 and 1 July 2001 from consecutive deliveries at the Vrije Universiteit Medical Center in Amsterdam. Singletons delivered via the vaginal route were included in the study. FHR recordings had duration of at least 1h prior to birth of the infant. Subdivision in three groups took place on the basis of the recording technique which had been used; i.e. ultrasound, scalp electrode or a combination of both methods. FHR data was obtained using HP-M1350 cardiotocographs. The status (pen on, pen off, maternal signal) and the mode of the signals were acquired. The duration of pen lifts and maternal signals was divided by the total duration of the recording. Statistical analyses were performed with the Mann-Whitney U-test and the Wilcoxon signed ranks test.

RESULTS

Recordings obtained via ultrasound demonstrated significantly more fetal signal loss than those obtained via the direct mode, particularly in the second stage. The FIGO criteria for fetal signal loss with external ultrasound were not fulfilled during this stage for about half the cases.

CONCLUSION

Intrapartum FHR monitoring via a scalp electrode provides far better quality FHR signals than external ultrasound and deserves a more prominent position in fetal surveillance than it currently has.

Laserspectroscopy in the fetus during labour

The newly available modified laserspectroscopy for fetal physiologic measurements provides information about biochemical parameters and is potentially an additional technique for fetal surveillance.

METHOD

Using laserspectroscopy it was possible to trace changes in absorbances at four different wavelengths and to calculate relative changes of HbO2, desaturated haemoglobin, total haemoglobin, and cytochrome aa3. Using an experimental set-up with fetal lamb during intermittend cord occlusion, we were able to study tissue oxygenation of the fetal brain (tpO2) under defined conditions. Furthermore, the NIR sensor was used during physiologic measurements in the human fetus.

RESULTS

As had been proposed earlier, it is obvious that the tolerance to hypoxia is increased after cord compression is repeated, as is indicated by the shifting of the cytochrome dissociation curve to the left. In the human fetus without fetal distress we observed stable values with only minor fluctuations related to changes of intrauterine pressure. On the other hand, in cases where there was an intrauterine complication the deterioration of oxygenation was detected form a decrease in HbO2 and cytochrome aa3.

DISCUSSION AND CONCLUSION

The routinely used CTG has been criticised for the effect of leading to an unacceptably high number of cesarean sections. Information on biochemical variables leads to better identification of fetal distress. In comparison to fetal blood sampling NIR laserspectroscopy holds the promise of a non-invasive tool providing continues monitoring.

Continuous spinal analgesia for labor and delivery in a parturient with hypertrophic obstructive cardiomyopathy

Induction of labor under analgesia was planned for a 30-year-old-primiparous patient with hypertrophic obstructive cardiomyopathy (HOCM), as her fetal evaluation revealed intrauterine growth restriction at 38 weeks' gestation. However, regional analgesia during labor may present a potential risk for hemodynamic instability in patients with HOCM due to the possibility of a sympathetic block, as a result of vasodilation associated with the administration of local anesthesia. This case report demonstrates the successful management of the patient with analgesia provided by a continuous spinal catheter dosed with a continuous infusion of fentanyl and supplemental meperidine. Fetal surveillance monitoring included fetal pulse oximetry in addition to conventional cardiotocography, on the basis of which cesarean section was avoided.

Systematic instrumental errors between oxygen saturation analysers in fetal blood during deep hypoxemia

BACKGROUND

During a study of artificially produced deep hypoxemia in fetal cord blood, systematic errors of three different oxygen saturation analysers were evaluated against a reference CO oximeter.

METHODS

The oxygen tensions (PO2) of 83 pre-heparinized fetal blood samples from umbilical veins were reduced by tonometry to 1.3 kPa (10 mm Hg) and 2.7 kPa (20 mm Hg). The oxygen saturation (SO2) was determined (n=1328) on a reference CO oximeter (ABL625, Radiometer Copenhagen) and on three tested instruments (two CO oximeters: Chiron865, Bayer Diagnostics; ABL700, Radiometer Copenhagen, and a portable blood gas analyser, i-STAT, Abbott). The CO oximeters measure the oxyhemoglobin and the reduced hemoglobin fractions by absorption spectrophotometry. The i-STAT system calculates the oxygen saturation from the measured pH, PO2, and PCO2. The measurements were performed in duplicate. Statistical evaluation focused on the differences between duplicate measurements and on systematic instrumental errors in oxygen saturation analysis compared to the reference CO oximeter.

RESULTS

After tonometry, the median saturation dropped to 32.9% at a PO2=2.7 kPa (20 mm Hg), defined as saturation range 1, and to 10% SO2 at a PO2=1.3 kPa (10 mm Hg), defined as range 2. With decreasing SO2, all devices showed an increased difference between duplicate measurements. ABL625 and ABL700 showed the closest agreement between instruments (0.25% SO2 bias at saturation range 1 and -0.33% SO2 bias at saturation range 2). Chiron865 indicated higher saturation values than ABL 625 (3.07% SO2 bias at saturation range 1 and 2.28% SO2 bias at saturation range 2). Calculated saturation values (i-STAT) were more than 30% lower than the measured values of ABL625.

CONCLUSION

The disagreement among CO oximeters was small but increasing under deep hypoxemia. Calculation found unacceptably low saturation.

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.

Monitoring technology and the clinical perspective

Currently available technology requires a new look to reduce intervention as well as to improve the detection of the truly at-risk fetus. Iatrogenic causes of so-called fetal distress, in particular the administration of uterotonics without due attention to avoiding hyperstimulation, predominate as a reason for intervention. There needs to be a better definition of the starting point, i.e assessment of the fetal condition and identification of any risk factors, such as oligohydramnios and growth retardation, that might diminish fetal reserve. This will allow 'customization' of surveillance and management according to the needs of each individual fetus. There also needs to be better training and better agreement about the end-point of monitoring. For prospective surveillance, the aim is to avoid rather than to identify damage, and the definition of the appropriate point for intervention needs to come from better consensus on what is and what is not acceptable management based on current knowledge. New technology holds the promise that it can give trended information during labour, allow early recognition of problems and reduce unnecessary intervention. However, there is a need to ensure reliability and reproducibility of the readings before a new method is released. Co-operation with industry is essential, but the roles need to be well defined and the ultimate responsibility for establishing the role of a new technique has to come from the clinicians involved in intrapartum care.

Developments in CTG analysis

FHR monitoring has been the subject of many debates. The technique, in itself, can be considered to be accurate and reliable both in the antenatal period, when using the Doppler signal in combination with autocorrelation techniques, and during the intrapartum period, in particular when the FHR signal can be obtained from a fetal ECG electrode placed on the presenting part. The major problems with FHR monitoring relate to the reading and interpretation of the CTG tracings. Since the FHR pattern is primarily an expression of the activity of the control by the central and peripheral nervous system over cardiovascular haemodynamics, it is possibly too indirect a signal. In other specialities such as neonatology, anaesthesiology and cardiology, monitoring and graphic display of heart rate patterns have not gained wide acceptance among clinicians. Digitized archiving, numerical analysis and even more advanced techniques, as described in this chapter, have primarily found a place in obstetrics. This can be easily explained, since the obstetrician is fully dependent on indirectly collected information regarding the fetal condition, such as (a) movements experienced by the mother, observed with ultrasound or recorded with kinetocardiotocography (Schmidt, 1994), (b) perfusion of various vessels, as assessed by Doppler velocimetry, (c) the amount of amniotic fluid or (d) changes reflected in the condition of the mother, such as the development of gestation-induced hypertension and (e) the easily, continuously obtainable FHR signal. It is of particular comfort to the obstetrician that a normal FHR tracing reliably predicts the birth of the infant in a good condition, which makes cardiotocography so attractive for widespread application. However, in the intrapartum period, many traces cannot fulfil the criteria of normality, especially in the second stage. In this respect, cardiotocography remains primarily a screening and not so much a diagnostic method. As long as continuous monitoring of fetal acid-base balance has not been extensively tested in clinical practice, microblood sampling of the fetal presenting part (Saling, 1994) is a useful adjunct. The problem with non-normal tracings is that their significance is very often unclear. They may indicate serious fetal distress, finally resulting in preventable destruction of critical areas in the fetal brain and damage to various organs; or, on the contrary, they may indicate temporary changes in cardiovascular control as a reaction to the intermittent effects on fetal haemodynamics of, for example, uterine contractions, whether or not in combination with partial or complete compression of umbilical cord vessels or the vessels on the chorionic plate (van Geijn, 1994). Many factors influence the FHR and its variability, which further complicates the interpretation of FHR patterns; some have been discussed here in some detail. Undoubtedly, there is a need for quantitative and objective FHR analysis, as long as it does not lead to erroneous results. Close collaboration between engineers and clinicians is a prerequisite for further advances in this field. Decision support systems certainly have a future but only if they are able to take into account a large set of clinical data and can combine it with data obtained from FHR signals and other parameters referring to the fetal condition, such as fetal growth, Doppler velocimetry, amniotic fluid volume and biochemical and biophysical data obtained from the mother. Basic technical concepts inherent in computerized CTG analysis, such as sampling rate (Chang et al, 1995), signal loss, artefact detection (van Geijn et al, 1980), further processing of intervals, archiving in digitized format and monitor display, should receive considerable attention. There is still a long way to go until decision support systems find their way into obstetric practice. Further developments can only be achieved thanks to efforts of many basic and clinical researchers, wo

Arterial oxygen saturation in relation to metabolic acidosis in fetal lambs

OBJECTIVE

We studied the relationship between preductal arterial oxygen saturation and metabolic acidosis in 18 chronically instrumented fetal lambs (gestational age 119 to 133 days) in two experimental designs. In the first group the onset of metabolic acidosis was determined. In the second group the progression of metabolic acidosis was studied as was the cardiovascular and hormonal changes resulting from hypoxemia.

STUDY DESIGN

In nine fetal lambs maternal fraction of inspired oxygen was lowered stepwise by increasing flows of nitrogen delivered into the trachea through a small indwelling catheter (group 1), and in nine fetal lambs maternal blood flow was reduced stepwise by means of a vascular occluder (group 2).

RESULTS

Baseline arterial oxygen saturation values ranged from 26% to 67% with normal pH and extracellular fluid base excess values in both groups 1 and 2. In both groups pH and extracellular fluid base excess started to decrease below 30% arterial oxygen saturation, with a progressive decrease below 20% arterial oxygen saturation to an end value for pH of 7.14. In some fetal lambs pH and extracellular fluid base excess decreased initially at 20% to 30% arterial oxygen saturation and then stabilized at the lower level. Fetal heart rate in group 1 increased during hypoxemia from 155 to 179 beats/min. In group 2 baseline fetal heart rate was 153 beats/min and fell with every step change in arterial oxygen saturation but subsequently increased to 172 beats/min by the end of the period of hypoxemia. Baseline values for epinephrine, norepinephrine, dopamine, cortisol, and mean arterial pressure were not related to baseline arterial oxygen saturation levels, and each of these variables was increased at the end of hypoxemia in group 2.

CONCLUSION

Preductal arterial oxygen saturation can reach values between 20% and 30% before anaerobic metabolism starts. During the progressive acidosis blood pressure was increased, which can be attributed to a strong rise in catecholamines.

Caesarean section in Britain and the United States 12% or 24%: is either the right rate?

The rate of caesarean section (CSR) in Great Britain (GB) and the U.S.A., 12% in England in 1989 ascertained from a survey performed by the authors, and 24% according to official U.S. figures, is higher than warranted by the known and agreed obstetric indications for this operation, which suggest a rate of 6-8% would be adequate. It is argued that the fall in perinatal mortality which has occurred over the period during which the CS rate has risen is not the main reason for this fall. The training of obstetricians to deal with anxiety, provision of primary maternity care by appropriately trained midwives and general or family practitioners, and changes in management protocols could cut the CSR. The number of women undergoing surgery every year in the U.K. could be reduced by 20,000 and in the U.S.A. by 470,000 if the rate of 6% were achieved. In studies of midwifery care the CSR is even lower and it is possible that labour proceeds more efficiently if the woman knows her caregivers and labours at home, as in The Netherlands. Although CS is much safer than in the past it is still more likely to result in the death of the woman and has significant morbidity for the woman and economic costs for society.

Fetal acidosis in labour: a prospective study on the effect of parity

The effect of parity on intrapartum fetal scalp pH was investigated in 6466 patients in labour with a live fetus who were delivered in 1987. 350 (5.4%) required fetal scalp blood sampling for pH (FBS), 236 primigravidae (10.4%) and 114 multigravidae (2.7%) (P less than 0.001). Fetal acidosis (pH less than 7.20) was detected in 35 patients, 27 primigravidae (11.4%) and 8 multigravidae (7.0%) (P less than 0.001). The incidence of intrapartum acidosis in the 2275 primigravidae and the 4191 multigravidae was 1.2 and 0.2% respectively (P less than 0.001). The two deaths from birth asphyxia and three cases of neonatal seizures occurred in primigravidae. In primigravidae requiring FBS, fetal acidosis was not associated with the use of oxytocin or with increased duration of labour. Neonatal seizures were more common overall in primigravidae than in multigravidae and more common in patients requiring FBS than in those not requiring FBS (P less than 0.05). The higher incidence of FBS, fetal scalp acidosis and neonatal seizures in primigravidae has important implications for intrapartum fetal monitoring.

Perinatal risk factors in birth asphyxia: relationship of obstetric and neonatal complications to neonatal mortality in 16,365 consecutive live births

Over a period of one year, 16,365 consecutively live born neonates were prospectively studied for evidence of birth asphyxia using the requirement of greater than one minute of positive pressure ventilation for identifying infants suffering from birth asphyxia. Asphyxia occurred in 2.8% of all neonates. Multivariate analysis of high risk factors associated with increased risk of asphyxia showed that low birth weight was the most significant predictor of asphyxia: asphyxia occurred in 68% of infants of less than 1,000 g birth weight and decreased to 1.2% in infants of 3-4 kg birth weight. Perinatal risk factors associated with a higher incidence of asphyxia include: postmaturity, birth weight (less than or equal to 2.5 kg) and with the presence of maternal and/or obstetric complications. The impact of asphyxia on neonatal mortality was most pronounced in more mature infants and the mortality was increased 3 fold in infants of less than 34 week gestation and greater than 27 fold for infants greater than 38 week gestation. Of the asphyxiated neonates, intrauterine growth retardation, fetal macrosomia, hypothermia, hyaline membrane disease, seizures, hypoglycemia and hyponatremia were significantly associated with an increased risk of death.

Fetal monitoring

This paper introduces fetal monitoring by describing the medical problems of the fetus in utero. The various methods currently used to monitor the fetus are reviewed with their respective advantages and shortcomings. New methods of surveillance of the fetus are highlighted as well as the mother's reaction to the technology.

Arterial PO2, PCO2, and pH versus transcutaneous PO2 and PCO2 and tissue pH in the fetal dog

In the fetal dog, simultaneous recording by transcutaneous PO2 and PCO2 and tissue pH electrodes were compared to corresponding arterial values during hypoxic episodes produced by occlusion of the maternal abdominal aorta. Before occlusion, the differences between the paired values were minimal. Under anoxic conditions, expected changes in the peripheral circulation were observed. However, the transcutaneous PO2 was lower, the transcutaneous PCO2 much higher, and the tissue pH much lower than in blood. Continuous electrodes demonstrate changes resulting from gas and hydrogen ion coming from cells more readily than blood because they are closer to the former. Additionally, carbon dioxide and hydrogen ion are buffered to a greater degree in blood than in cells. Consequently, under conditions of stress and active metabolism, PCO2 is higher while PO2 and pH are lower in cells than in blood. When compared with monitoring of gases and acid-base balance through blood sampling, continuous transcutaneous and intracutaneous monitoring would seem to be more representative of the environment at the cellular level.

Fetal acid-base balance in low-risk patients in labor

The fetal acid-base balance from scalp blood in the early and late first stage of labor and from cord arterial blood was assessed in 120 low-risk patients only monitored electronically for 15 minutes at admission. The mean scalp blood pH values were 7.332 at a cervical dilatation of 5 cm and 7.335 at 10 cm cervical dilatation. A low pH value (less than 7.25) was found in 14 patients; five (4.2%) of them had fetal distress. Stethoscopic auscultation failed to identify these cases. Another nine patients had transient abnormal acid-base balance (a check value within 30 minutes was normal), and the fetal heart rate trace (obtained immediately after the sampling) showed no ominous changes in these cases. It is concluded that an abnormal fetal acid-base balance is not uncommon in a low-risk population in labor. However, a critical evaluation of the acid-base balance is necessary, since in most cases the abnormal acid-base balance is transient and of a respiratory, innocuous type without concomitant fetal distress.

Continuous, noninvasive measurement of fetal oxygen and carbon dioxide levels in labor by use of mass spectrometry

Clinical evaluation of the continuous, simultaneous measurement of fetal scalp surface oxygen and carbon dioxide partial pressures by mass spectrometry was undertaken for 52 labors. The mass spectrometer (MM8-80, V.G. Gas Analysis, Winsford, England) was easy to operate and had good long-term stability. The mean drifts for both oxygen and carbon dioxide over the study periods were less than 2 mm Hg. The mean (+/- SD) cervical dilatation at the time of transducer application was 6.1 (+/- 1.9) cm and the mean (+/- SD) duration of the studies was 169 (+/- 122) minutes; 10.5% of the transducer applications were unsuccessful. Falls in fetal scalp surface oxygen levels and rises in carbon dioxide levels were more frequent with late than with variable and with variable than with early fetal heart rate decelerations and with increasing severity and frequency of decelerations. Fetal scalp surface pressure changes also occurred with fetal heart rate variability changes, including some related to behavioral state changes. There was not a constant reciprocal relationship between oxygen and carbon dioxide changes, and fetal heart rate patterns were not related to actual blood gas levels. Fetal scalp surface measurements were related to both fetal blood sample and umbilical artery results. Trends in both oxygen and carbon dioxide levels during the course of labor were compared and related to other fetal variables, and most of the time the scalp surface measurements were an accurate guide to systemic blood gas levels. Maternal oxygen administration resulted in significant increase in fetal scalp surface oxygen levels, and on two of eight occasions it also led to decreases in fetal carbon dioxide levels. Scalp surface gas measurement by means of mass spectrometry is a powerful new method of intrapartum fetal monitoring, which should increase the precision of fetal surveillance as well as allow the accurate assessment of both established and new methods for optimizing labor and delivery.

Effect of delays in collection or analysis on the results of umbilical cord blood measurements

Changes in umbilical cord blood pH, PO2 and PCO2 were measured when blood was stored in preheparinized polyethylene syringes in the refrigerator for up to 6 h after delivery, and when there was delayed sampling up to 1 h after delivery from umbilical cord segments left at room temperature. Blood stored in the refrigerator usually showed a decrease in pH and increases in PO2 and PCO2, but the mean rates of change were small: -0.005 units/h for pH; +0.06 kPa/h for PCO2 and +0.03 kPa/h for PO2. Changes in the three variables in blood collected from umbilical cords up to 1 h after delivery were small and not systematic. Much of the variation was within the limits of accuracy of the ABL-3 (Radiometer) blood-gas analyser. The results showed that while immediate collection and analysis of umbilical cord blood is advisable for the greatest accuracy, it is not essential. As long as the delay is not excessive, the results can still be used as a useful guide to the biochemical condition of an infant at birth.

The use of intrapartum fetal blood lactate measurements for the early diagnosis of fetal distress

Lactate concentrations were measured during labor and at delivery in blood samples from the fetal presenting part and from the umbilical cord with the use of a rapid electrochemical technique. The value of these measurements to discriminate between normal and distressed fetuses was compared to that of pH, base excess, PCO2 and PO2 measurements in the same blood samples. The fetuses were divided into three groups, normal, prepathologic, and pathologic, according to the presence and severity of fetal distress as evaluated by Apgar score, intrapartum cardiotocography, meconium staining of the amniotic fluid, and cord arterial pH at birth. Lactate and pH provided the best parameters to distinguish between groups, with lactate having the most discriminating power at least in early labor and midlabor. The prospective value of discriminant functions derived from lactate and pH data was good when the fetuses were allocated into the normal group but poor when an attempt was made to allocate the fetuses into prepathologic and pathologic groups, with a high false negative rate. However, the discriminating ability was improved when prepathologic and pathologic fetuses were included into one single abnormal group. These results confirm the potential use of rapid fetal blood lactate measurements for the early diagnosis of intrapartum fetal distress.

Fetal distress and the condition of newborn infants

In a prospective audit of the obstetric management of 1210 consecutive deliveries the association was investigated between the need for operative delivery for fetal distress during labour and the condition of the newborn infant. Operative delivery was performed for only 11.5% of the newborn infants with severe acidosis at birth (umbilical artery pH less than 7.12, base deficit greater than 12 mmol (mEq)/1), 24.1% of those with an Apgar score less than 7 at one minute, and 15.8% of those with both severe acidosis and a one minute Apgar score less than 7. Most of the infants delivered operatively were in a vigorous condition at birth and did not have severe acidosis. Fetal blood sampling was done in 4.0% of labours. As none of the fetal blood values were less than 7.20 and only three of the infants sampled in utero suffered severe acidosis at birth, fetal blood sampling would have had to be performed much more often to provide a useful guide to metabolic state at birth. While the large majority of "at risk" fetuses had continuous fetal heart rate monitoring in labour, this had not been provided in 48.7% of the labours of infants with severe acidosis, 38.7% of infants with a one minute Apgar score less than 7, and 47.4% of infants with both severe acidosis and a one minute Apgar score less than 7. Continuous fetal heart rate monitoring was associated with a much higher incidence of operative delivery for fetal distress than was intermittent fetal heart rate auscultation. These results suggest an urgent need to review present methods for assessing the intrapartum condition of the fetus, making the diagnosis of fetal distress, and assessing the condition of the infant at birth.

[Hypoxia during the perinatal period and the formation of cerebral lesions]

The degree of hypoxia and the cerebral blood flow are of outstanding importance in the pathogenesis of cerebral damage due to perinatal hypoxia. Nevertheless many other factors influence origin, extension and localisation of cerebral damage. An acute total ischemia results especially in disorders of brainstem, inferior colliculi and thalamic nuclei while the most frequent type, the partial ischemia, manifests in cortical regions. In immature newborn infants, posthypoxic lesions are usually located periventricular, in mature infants, cortically. Brain edema preferentially occurring in mature infants damages CNS additionally. This danger is enhanced by supplementation of glucose before hypoxia resulting in accumulation of even more lactic acid. Intracerebral hemorrhages predominantly occur in immature infants. One speculates that they are caused by rupture of thin capillary walls of germinal matrix. Due to impaired autoregulation of cerebral blood flow after perinatal hypoxia, these vessels are exposed to every change of arterial blood pressure. Therefore therapy of metabolic acidosis and posthypoxic circulatory insufficiency may contribute to intracerebral hemorrhage too.

Elective fetal monitoring and obstetrical operative frequency

This paper reports on cardiotocographic findings after the introduction of elective fetal monitoring. A classification into the following four groups is recommended: normal, warning, severe functional hemodynamic disorders (SFHD) and hypoxia. This fetal heart frequency (FHF) classification prefers the evaluation of the effects on fetal condition compared with a descriptive classification. SFHD in the first stage of labor can be observed in 4% of parturient women, increasing to nearly 16% in the second stage. Cesarean section rate in this group amounts to 12.5% and forceps rate exceeds 50%. Under the condition of elective fetal monitoring (94% in total) and a reserved application of cesarean section (4.3% in total) and generous forceps delivery (15% in total) a perinatal mortality rate of 13% for obstetrical material with high-risk concentration is achieved. The total acidosis rate (pH less than 7.20) decreases to 2.3%, whereas the rate of severe acidosis (pH less than 7.10) was observed in only 0.4% of the cases. With elective fetal monitoring a low cesarean section rate taking critical evaluation into consideration and using all conservative methods of treatment is obtained. By means of the generous application of the single or repeated bolus injection of 25 micrograms fenoterol and the operative shortening of the second stage of labor in the case of SFHD, the neonatal morbidity can be kept at a low level. The small number of fetal or maternal complications using the direct methods of fetal supervision and the careful operative termination of labor justifies the recommended obstetrical management.

Neonatal morbidity in deliveries conducted by midwives and gynecologists. A study of the system of obstetric care prevailing in The Netherlands

The efficacy of the Dutch system of obstetric care was investigated by comparison of the outcomes of two groups of supposedly normal first pregnancies and deliveries that were solely cared for by midwives (n = 85) or by gynecologists (n = 27). The outcome was measured by pH, PCO2, and base deficit in arterial cord blood (early morbidity) and by neurological examination with Prechtl's method (late morbidity). The occurrence of 10 neurologically nonoptimal infants in the midwife group is thought incompatible with the basis philosophy of the Dutch obstetric system, which is that midwives are able to select the normal pregnancies out of the group of women who present for obstetric care and can assist in maintaining the normal state in these selected cases in the course of delivery. The acid-base values were less favorable in the midwife group than in the gynecologist group. Neurological nonoptimality in the midwife group was related to acidosis. The influence of the site of birth (home or hospital--ambulatory) could be virtually ruled out.

The development of fetal acidosis in the presence of an abnormal fetal heart rate tracing. I. The average for gestational age fetus

An abnormal fetal heart rate (FHR) tracing is a sensitive indicator of positivity that disease exists, but the intrinsic predictive value of such a tracing is disappointingly low because of the large number of false positive results. Abnormal FHR tracings, defined as those having a persistent quantitative score of 4 or less, were measured against time and outcome. A baseline fetal scalp blood sample was taken. Twenty fetuses were acidotic at the first blood sample. There were 121 study cases, all of which were greater than 37 weeks' gestational age. All fetuses were average for gestational age. Amniotic fluid was clear, internal FHR tracings were initially normal, and the first pH was normal. A relative acidosis-free interval could be demonstrated during the first 90 to 100 minutes. Following this time period rapid cumulative acidosis was seen, which varied according to the FHR pattern observed. The P50 acidosis values for various patterns were late decelerations, 115 minutes; variable decelerations, 145 minutes; and flat line tracings, 185 minutes.

Continuous transcutaneous oxygen monitoring in fetal surveillance during labor

Continuous transcutaneous oxygen (PtcO2) monitoring is a noninvasive technique for recording changes in central oxygenation. PtcO2 monitoring has been for some years a routine method in neonatal and adult intensive care. The technique is a potential tool in fetal surveillance during labor. Some recently published studies which have been critical of the use of PtcO2 monitoring in the delivery room reveal a lack of thorough understanding of the limitations of the technique. From the author's experience with the technique, it is obvious that, when the PtcO2 electrode is attached according to recommendations and when the monitoring situation fulfills certain criteria, PtcO2 reliably reflects changes in the fetal oxygenation during labor and may be used for the diagnosis of true hypoxemia. PtcO2 monitoring does not replace any other available routine monitoring for fetal surveillance, but when the technique is refined, it may become an additional means of diagnosing fetal jeopardy. As a research parameter, PtcO2 monitoring has already contributed to a more diversified understanding of the process of fetal asphyxia.

Impact of routine fetal monitoring during labor on fetal outcome with long-term follow-up

A computerized system for the storage of antenatal, intrapartal, and neonatal data has been used since 1973. The present study evaluated the influence of changed neonatal and obstetric practices, with special regard to routine fetal monitoring. Three periods were studied: 1973-1974 (6,542 deliveries, only selected high-risk patients monitored); 1975-1976 (6,857 deliveries, high-risk patients monitored); 1977-1979 (9,638 deliveries, 90% monitored). The numbers of infants with an Apgar score less than 7 at 1 and 5 min were similar in 1973-1974 and 1975-1976, but the number was significantly reduced in 1977-1979. During the years studied, all but eight infants with an Apgar score less than 7 at 5 min participated in a scheduled long-term follow-up (at least 14 mo). In 1973-1974, 25 infants (35.2%) demonstrated neurological handicaps. In 1975-1976, 14 infants (19.2%) had sequelae; in 1977-1979, only three infants (4.6%) were damaged. Trend analysis showed a significant reduction in the number of infants with neurological sequelae through the years; the reduction was significant for premature and low-risk infants but not for mature high-risk infants. The improved short-term and long-term fetal outcomes seem to be largely a result of routine fetal monitoring with all its implications for obstetric and neonatal management; the significant reduction in neurological sequelae, even after correction for other changes in obstetric routines, supports this suggestion.