Fetal Heart Rate Recordings Research Articles

Circadian Rhythms in Infants

After completing this article, readers should be able to: 1. Describe how circadian rhythms are generated. 2. Describe how lighting influences the circadian system. 3. Delineate the period during which the origin of circadian rhythms develops. 4. Describe the relationship between maternal circadian rhythms and the development of circadian rhythms in infants. 5. Characterize the potential sequelae of impaired fetal and early neonatal circadian rhythms related to sleep patterns. 6. Describe beneficial lighting patterns for preterm infants in the neonatal intensive care nursery. Circadian rhythms are endogenously generated rhythms that have a period length of about 24 hours. Evidence gathered over the past decade indicates that the circadian timing system develops prenatally, with the suprachiasmatic nuclei (SCN) in the anterior hypothalamus, the site of a circadian clock, present by mid-gestation in primates. Recent evidence also shows that the circadian system of primate infants is responsive to light at very early stages (as early as 25 to 28 weeks’ gestation in humans) and that low-intensity lighting can regulate the developing clock. After birth, circadian system outputs mature progressively, with rhythms in sleep-wake cycles, body temperature, and hormone production generally developing between 1 and 3 months of age. The importance of light in regulation of circadian rhythm in infants is highlighted by the early establishment of rest-activity patterns that are in phase with the 24-hour light-dark cycle in preterm infants exposed to low-intensity cycled lighting. With the continued elucidation of circadian system development and influences on human physiology and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of neonatal care. ### The Circadian Timing System Notable examples of circadian rhythms include the sleep-wake cycle and daily rhythms in body temperature and hormone production. Circadian rhythms are also involved in the pathogenesis of illnesses, such as reactive airway disease (eg, asthma) and myocardial infarction. The system responsible …

A cost study of prenatal telemedicine.

We calculated the cost of using a telemedicine system for the cardiotocographic (CTG) recording of fetal heart rate. In a one-year study in the Campania region of Italy, 162 patients were monitored. The total cost of the telemedicine system was euro;344796. A control group was retrospectively drawn from all deliveries at the university hospital in Naples during the year 2000. Patients were retrospectively assigned to a category of high or low risk, and the hospital costs of the high-risk patients were compared. In the intervention group, 11 of the 87 high-risk patients (13%) were admitted to hospital prematurely, and stayed on average 12 days. In the control group, 203 of the 813 women in the high-risk group (25%) were admitted to hospital prematurely, and stayed on average 20 days. If the women in the control group had been monitored, there would have been a notional saving, through avoided bed days, amounting to 358280, which was similar to the cost of the telemedicine system. The study suggests that the use of telemedicine in CTG monitoring improves the quality of prenatal care.

Acute increase of umbilical artery vascular flow resistance in compromised fetuses provoked by uterine contractions

Background: An impaired placental circulation is involved in the mechanism of late fetal heart rate (FHR) decelerations. Objectives: To explore umbilical artery (UA) Doppler velocimetry changes in response to uterine contractions during the oxytocin challenge test (OCT) and assess the potentially clinical value of ‘OCT Doppler velocimetry’. Methods: 111 women with pregnancy complications were subjected to an OCT with simultaneous recordings of FHR and UA pulsatility index (PI). Positive OCT cases (late FHR decelarations) were compared with negative OCT cases (normal FHR patterns). Only negative OCT cases were allowed a trial of vaginal delivery. Results: The UA PI was higher in OCT positive ( N=21) than in negative cases ( N=90) during uterine contractions and relaxations ( P<0.05), but not during basal measurements. A positive OCT, but not negative, was associated with an increase of PI during contractions and relaxations compared with basal measurements ( P<0.05). Fetal growth restriction ( N=58), operative delivery for fetal distress (ODFD) in labor ( N=10), and birth asphyxia ( N=8) were not associated with PI changes significantly different from cases without these complications. Conclusions: During uterine contractions and relaxations, but not during basal measurements, a significantly higher UA PI evolved in OCT positive cases compared with OCT negative cases. This indicates a pathophysiological mechanism disclosed only during uterine activity. Although these changes would not have been revealed by traditional Doppler velocimetry, the data suggest a limited predictive value of ‘OCT Doppler velocimetry’ on the short-term neonatal outcome.

Diurnal variations in baseline fetal heart rate, maternal heart rate and movement in a twin pregnancy

In order to clarify the relationship between the diurnal variations in baseline fetal heart rate (BFHR) and maternal factors, simultaneous 24 h recordings of fetal heart rate, maternal heart rate (MHR) and maternal movement (MM) were made on one pregnant woman with a monochorionic twin pregnancy at 31, 34 and 36 weeks. The diurnal variations in BFHR of twins were highly correlated with no phase-lag. Although BFHR was correlated with MHR and MM at 31 and 36 weeks with phase-lag, there was no correlation between them at 34 weeks, despite the synchronization of BFHR between twins. It was suggested MHR and MM might not drive the diurnal variation of BFHR directly, because BFHR, MHR and MM did not always correlate.

Continuous systolic blood pressure monitoring by the difference in electrocardiogram and pulse oximetry in near-term, exteriorized goat fetuses.

Our purpose was to determine whether systolic arterial pressure, as predicted from the delay time from the electrocardiogram to pulse oximeter waveform, correlates with directly measured systolic blood pressure. Six Japanese Saanen goats at 120-125 days' gestation were used. Experiments were conducted in acutely operated animals under anesthesia. We placed catheters in the carotid artery and jugular vein, electrodes on the chest, and a pulse oximeter probe on the tongue. Systolic blood pressure (Psm), fetal heart rate (FHR), delay time (Td), and pulse oximeter waveform were monitored continuously, and the data were stored. Systolic blood pressure was estimated (Pse) by the simple linear equation of Td. Fetal blood pressure was decreased 10% by hydralazine and blood withdrawal. Correlation coefficients and the agreement between Psm and Pse were determined. A significant correlation (P <.01) with good bias values (< 8 mmHg) and precision values (< 5 mmHg) was obtained between Psm and Pse in all animals. There was also a significant correlation between Psm and Pse with high coefficients for hydralazine (r(2) = 0.82 +/- 0.12) and for withdrawal (r(2) = 0.85 +/- 0.15). The correlations became slightly scattered in acidemia (pH < 7.25). This technique has the potential to provide information on fetal blood pressure during labor and delivery on a beat-by-beat basis, which will aid in the interpretation of electronic FHR recordings.

The effect of a nitric oxide donor on fetal heart rate patterns in patients with hypertension

OBJECTIVE: To estimate whether nitric oxide donors can be administered safely to patients with pregnancy-associated hypertension based on computer analysis of antepartum fetal heart rate (FHR) tracings. METHODS: Thirty-minute recordings of FHR and fetal movements, before (stage I) and after (stage II) sublingual administration of 5 mg of isosorbide dinitrate, a nitric oxide donor, were obtained in 20 women with pregnancy-associated hypertension. RESULTS: Baseline FHR in stage I did not differ significantly from that in stage II (140.9 ± 2.0 beats per minute and 137.5 ± 2.1 beats per minute, respectively). There were no significant differences between stage I and II in the number (9.67 ± 1.14 versus 9.56 ± 1.07), amplitude (26.14 ± 1.03 versus 24.5 ± 0.85 beats per minute), and duration (36.03 ± 1.46 versus 34.04 ± 1.57 seconds) of heart rate accelerations. During stage II, the number (1.39 ± 0.43) and duration (26.9 ± 1.38 seconds) of heart rate decelerations did not change significantly as compared with stage I (1.67 ± 0.33 and 26.23 ± 1.13 seconds, respectively). However, the amplitude of heart rate decelerations was significantly higher in stage I compared with stage II (−19.36 ± 1.44 versus −14.38 ± 1.55 beats per minute, respectively). There were more fetal body movements during stage II than stage I (12.39 ± 2.8 versus 9.72 ± 2.0), but the difference was not statistically significant. CONCLUSION: Based on numeric analysis of FHR records, our data suggest that short-acting donors of nitric oxide can be administered safely to patients with pregnancy-associated hypertension.

Computerised intrapartum diagnosis of fetal hypoxia based on fetal heart rate monitoring and fetal pulse oximetry recordings utilising wavelet analysis and neural networks.

To develop a computerised system that will assist the early diagnosis of fetal hypoxia and to investigate the relationship between the fetal heart rate variability and the fetal pulse oximetry recordings. Retrospective off-line analysis of cardiotocogram and FSpO2 recordings. The Maternity Unit of the 2nd Department of Obstetrics and Gynaecology, Aretaieion Hospital, University of Athens. Sixty-one women of more than 37 weeks of gestation were monitored throughout labour. Multiresolution wavelet analysis was applied in each 10-minute period of second stage of labour focussing on long term variability changes in different frequency ranges and statistical analysis was performed in the associated 10-minute FSpO2 recordings. Self-organising map neural network was used to categorise the different 10-minute fetal heart rate patterns and the associated 10-minute FSpO2 recordings. Umbilical artery pH of < or = 7.20 and Apgar score at 5 minutes of < or = 7 formed the inclusion criteria of the risk group. After using k-means clustering algorithm, the two-dimensional output layer of the self-organising map neural network was divided into three distinct clusters. All the cases that mapped in cluster 3 belonged in the risk group except one. The sensitivity of the system was 83.3% and the specificity 97.9% for the detection of risk group cases. A relationship between the fetal heart rate variability in different frequency ranges and the time in which FSpO2 is less than 30% was noticed. Fetal pulse oximetry seems to be an important additional source of information. Computerised analysis of the fetal heart rate monitoring and pulse oximetry recordings is a promising technique in objective intrapartum diagnosis of fetal hypoxia. Further evaluation of this technique is mandatory to evaluate its efficacy and reliability in interpreting fetal heart rate recordings.

Computerised intrapartum diagnosis of fetal hypoxia based on fetal heart rate monitoring and fetal pulse oximetry recordings utilising wavelet analysis and neural networks

Objective To develop a computerised system that will assist the early diagnosis of fetal hypoxia and to investigate the relationship between the fetal heart rate variability and the fetal pulse oximetry recordings. Design Retrospective off-line analysis of cardiotocogram and FSpO 2 recordings. Setting The Maternity Unit of the 2nd Department of Obstetrics and Gynaecology, Aretaieion Hospital, University of Athens. Population Sixty-one women of more than 37 weeks of gestation were monitored throughout labour. Methods Multiresolution wavelet analysis was applied in each 10-minute period of second stage of labour focussing on long term variability changes in different frequency ranges and statistical analysis was performed in the associated 10-minute FSpO 2 recordings. Self-organising map neural network was used to categorise the different 10-minute fetal heart rate patterns and the associated 10-minute FSpO 2 recordings. Main outcome measures Umbilical artery pH of ≤7.20 and Apgar score at 5 minutes of ≤7 formed the inclusion criteria of the risk group. Results After using k-means clustering algorithm, the two-dimensional output layer of the self-organising map neural network was divided into three distinct clusters. All the cases that mapped in cluster 3 belonged in the risk group except one. The sensitivity of the system was 83.3% and the specificity 97.9% for the detection of risk group cases. Conclusions A relationship between the fetal heart rate variability in different frequency ranges and the time in which FSpO 2 is less than 30% was noticed. Fetal pulse oximetry seems to be an important additional source of information. Computerised analysis of the fetal heart rate monitoring and pulse oximetry recordings is a promising technique in objective intrapartum diagnosis of fetal hypoxia. Further evaluation of this technique is mandatory to evaluate its efficacy and reliability in interpreting fetal heart rate recordings.

Analysis of the influence of diurnal variation in maternal movements on fetal heart rate acceleration.

To determine the influence of diurnal variation in maternal movements (MM) on fetal heart rate (FHR) accelerations, 24-hour maternal heart rates (MHR), MM and FHR recordings were made simultaneously on nine healthy pregnant women at 36-39 weeks of gestation. Correlations between the diurnal variations in maternal factors and FHR parameters; that is, baseline FHR, amplitude, duration and hourly percentage of time spent in accelerations, were examined. Only a few cases showed a significant correlation between acceleration parameters and the diurnal variation of MHR or MM, while most cases indicated a high correlation between the diurnal variation in baseline FHR and that of maternal factors. In conclusion, the occurrence and form of accelerations might be independent of maternal activity.

Characteristics of maternal heart rate patterns during labor and delivery

OBJECTIVE: To find patterns characteristic of maternal heart rates recorded by an electronic fetal monitor and compare them with concomitant fetal heart rate (FHR) patterns. METHODS: Maternal heart rates and FHRs during active labor and delivery were simultaneously recorded in 26 parturients with singleton pregnancies in vertex presentation. The FHRs were obtained by an external ultrasound transducer or via a spiral scalp electrode and maternal heart rates by a triple-wire cable with electrocardiographic electrodes attached to the chest. Representative tracings of 30–60 minutes duration were selected from all stages of labor and after delivery of the placenta. Quantitative assessments were carried out under guidelines from the National Institute of Child Health and Human Development after blinding the source of these tracings. Patterns were compared by appropriate statistical analyses. RESULTS: Baseline maternal heart rates were significantly lower and their variability significantly higher than FHRs during all stages of labor. Maternal heart rates showed no decelerations; the proportion of tracings with accelerations increased as labor advanced, most of them coinciding with uterine contractions or bearing down efforts. The FHRs had both decelerations and accelerations. However, tracings with only accelerations (and no decelerations) were observed in decreasing frequency as labor advanced. Maternal accelerations had higher amplitudes and longer durations than fetal accelerations, especially in the second stage of labor. CONCLUSION: Maternal heart rate patterns recorded by electronic fetal monitors closely resemble fetal patterns. Baseline “fetal bradycardia,” the absence of decelerations in the second stage of labor, and marked accelerations coinciding with uterine contractions may suggest a maternal heart rate rather than an FHR recording.

The prediction and prevention of intrapartum fetal asphyxia in preterm pregnancies

Objective: This study was undertaken to examine the contribution of electronic fetal heart rate monitoring in the prediction and prevention of intrapartum fetal asphyxia in the preterm pregnancy. Study Design: The outcome of 40 pregnancies with biochemically confirmed intrapartum fetal asphyxia (ie, an umbilical artery base deficit >12 mmol/L) was examined. This included 20 pregnancies that were delivered abdominally matched with 20 pregnancies that were delivered vaginally. Antepartum and intrapartum clinical risk factors and newborn complications were documented. The interpretation of the fetal heart rate record as determined by the responsible clinicians was recorded. Fetal asphyxia was classified as mild, moderate, or severe on the basis of an umbilical artery base deficit of >12 mmol/L and newborn encephalopathy and other organ system complications. Results: Fetal asphyxia was classified as mild in 21 pregnancies and as moderate or severe in 19 pregnancies. The fetal heart rate record was predictive of fetal asphyxia in 27 pregnancies and nonpredictive in 11 pregnancies. The predictive fetal heart rate record was the primary indication for intervention in 21 of the 24 pregnancies that were delivered by cesarean delivery in the first stage or operative vaginal delivery in the second stage of labor. Newborn outcome may have been influenced by intervention and delivery because of a predictive fetal heart rate record in 10 pregnancies with mild fetal asphyxia and in 9 pregnancies with moderate or severe fetal asphyxia. Conclusion: Electronic fetal monitoring is a useful screening test for the prediction of intrapartum fetal asphyxia in the preterm pregnancy. A predictive fetal heart rate record was the principle indication that led to intervention and delivery. A prediction of fetal asphyxia that leads to intervention and delivery may prevent or modify moderate or severe newborn morbidity as the result of fetal asphyxia. (Am J Obstet Gynecol 2002;186:279-82.)

Fetal and maternal cardiovascular diurnal rhythms in pregnancies complicated by pre-eclampsia and intrauterine growth restriction

Objectives: To determine whether the diurnal blood pressure profiles in pregnant women with pre-eclampsia and/or intrauterine growth restriction (IUGR) differ from those in normal pregnant controls,and, if so, to establish whether such a difference is accompanied by altered diurnal rhythms of fetal heart rate (FHR) and its variation.Methods: Twenty-two women in the third trimester of pregnancywith pre-eclampsia, IUGR, or both, entered the study. Eleven healthy pregnant women served as controls. Maternal systolic and diastolic blood pressures and heart rate (MHR) were determined automaticallyat 30-min intervals during a period of 26 h starting at 09.00. During the study period, nine 1-h recordings of FHR were made at predetermined timepoints. FHR was analyzed numerically.Results: Systolicand diastolic blood pressures and MHR showed diurnal patterns, with the highest values during the day and a trough during the night in all women. Daytime and night-time blood pressures were higher in pre-eclampticwomen (p < 0.001), and the day-night difference was smaller than in controls (p < 0.001). Diurnal patterns of FHR and its variation did not differ qualitatively between the three studygroups. However, FHR was affected by the maternal blood pressure profile, and all FHR parameters and their diurnal ranges were quantitatively different in IUGR fetuses (p < 0.05).Conclusion:In pre-eclamptic women, there was blunting of the diurnal blood pressure profile. This altered maternal hemodynamics was associated with a similar reduction in FHR amplitude during the 26-h period butnot with FHR variation. Although diurnal rhythms of FHR and its variation persisted qualitatively in the IUGR fetuses, they seemed to have been reset quantitatively, leading to a flattened diurnal pattern.

Cardiac troponin I and N-terminal pro-brain natriuretic peptide in umbilical artery blood in relation to fetal heart rate abnormalities during labor.

The use of continuous fetal heart rate (FHR) recordings to monitor fetal well-being during labor is standard clinical practice in developed countries. Little is known about the relationship, if any, that exists between these FHR abnormalities and the fetal cardiac musculature and function. The aim of this study was to investigate umbilical artery serum levels of cardiac troponin I, a sensitive and specific marker of myocardial necrosis, and N-terminal pro-brain natriuretic peptide (pro-BNP), a sensitive marker of left ventricular dysfunction, in relation to FHR abnormalities. Umbilical artery blood samples were taken from 27 cases immediately after delivery of the infant. There was evidence of significant FHR abnormalities in 11 of these cases (group 2) and the FHR recording was normal in 16 cases (group 1). The mean N-terminal pro-BNP level in umbilical artery serum in group 2 was 413 fmol/L (SEM = 85) and in group 1 was 223 fmol/L (SEM = 28)(p = 0.022). There was no significant difference observed in cardiac troponin I levels between the two groups. Umbilical artery serum N-terminal pro-BNP is elevated in association with fetal heart rate abnormality in the late stage of labor. This finding suggests that some degree of cardiac compromise accompanies FHR abnormality.

Computerised antenatal fetal heart rate recordings between 24 and 28 weeks of gestation.

To assess computerised fetal heart rate recordings between 24 and 28 weeks of gestation for gestation related differences. Prospective, cross sectional observational study. Liverpool Women's Hospital. 112 women: 28 at 27 weeks, 30 at 26 weeks, 27 at 25 weeks and 27 at 24 weeks of gestation, respectively. Fetal heart recordings of 60 minutes duration were performed once in each pregnancy using the System 8000 fetal heart rate programme (System 8000, Oxford Sonicaid Ltd, Chichester, UK). For each gestational age, records were analysed for short term variation, basal heart rate, accelerations and time spent in high episodes. The mean short term variation increased with gestation (P = 0.05). No record had a short term variation <4 msecs. There was no relationship between heart rate and increasing gestation. The mean number of accelerations per record increased with increasing gestation (P < 0.01). 20% of recordings showed no accelerations > 15 bpm. The mean duration spent in episodes of high variation increased with gestation (P = 0.05). 13% of recordings showed no time spent in high episodes. All fetuses had normal outcomes at delivery. Absence of episodes of high variation or absence of accelerations is not an abnormal finding at lower gestations. The standard threshold of 4 msecs for short term variation appears to remain valid at lower gestations. These differences should be considered when using computerised CTG analysis at early gestations.

Computerised antenatal fetal heart rate recordings between 24 and 28 weeks of gestation

Objective To assess computerised fetal heart rate recordings between 24 and 28 weeks of gestation for gestation related differences. Design Prospective, cross sectional observational study. Setting Liverpool Women's Hospital. Population 112 women: 28 at 27 weeks, 30 at 26 weeks, 27 at 25 weeks and 27 at 24 weeks of gestation, respectively. Methods Fetal heart recordings of 60 minutes duration were performed once in each pregnancy using the System 8000 fetal heart rate programme (System 8000, Oxford Sonicaid Ltd, Chichester, UK). For each gestational age, records were analysed for short term variation, basal heart rate, accelerations and time spent in high episodes. Results The mean short term variation increased with gestation ( P=0.05). No record had a short term variation <4 msecs. There was no relationship between heart rate and increasing gestation. The mean number of accelerations per record increased with increasing gestation ( P<0.01). 20% of recordings showed no accelerations >15 bpm. The mean duration spent in episodes of high variation increased with gestation ( P=0.05). 13% of recordings showed no time spent in high episodes. All fetuses had normal outcomes at delivery. Conclusions Absence of episodes of high variation or absence of accelerations is not an abnormal finding at lower gestations. The standard threshold of 4 msecs for short term variation appears to remain valid at lower gestations. These differences should be considered when using computerised CTG analysis at early gestations.

A longitudinal study of diurnal variation in baseline fetal heart rate in one dichorionic‐diamniotic twin pregnancy

A longitudinal study to analyse the diurnal variations in baseline fetal heart rate (FHR) and sustained fetal tachycardia (SFT) in twin pregnancy was performed on one dichorionic twin. Twenty-four hour FHR recordings on twins were made at 32, 34 and 36 weeks of gestation simultaneously. Significant diurnal variations were found in both twins in all gestational weeks. The diurnal variations in baseline FHR of twins were highly correlated with no phase-lag. No coincidence was recognized in the appearance of SFT between twins. These results suggest the maternal influence equally affects FHR in each fetus of dichorionic twin since 32 weeks of gestation, while the appearance of SFT might be independent from maternal influence.

Effects of morphine and naloxone on fetal heart rate and movement in the pig.

To test the hypothesis that an increasing opioid tonus is involved in decreases in fetal heart rate (FHR) and movement (FM) during late gestation, we studied the effects of intravenous bolus injections of morphine (1 mg) and naloxone (1 mg) on FHR and FM in the fetal pig. Twenty-one fetuses (1 per sow) were catheterized at 90-104 days of gestation (median 100 days). Recordings of FHR (electrocardiograph or Doppler-derived signals) and FM (ultrasonography) were made from 15 min before to 45 min after treatment. Morphine administration significantly decreased FHR, but it increased FHR variation and forelimb movements (LM). LM were clustered, and this stereotyped behavior has never before been observed in any mammalian fetus. Naloxone administration increased gross body movements and FHR without significant changes in FHR variation. It is concluded that FHR and motility are under opioidergic control in the pig fetus. Both morphine and naloxone induce hypermotility, suggesting that naloxone does not act as a pure opioid antagonist in the fetal pig.

Fetal Circulatory Responses to Maternal Blood Loss

We examined the fetal circulatory responses to maternal blood loss in pregnant women during the third trimester. Seven healthy women with placenta previa and singleton pregnancies underwent phlebotomies in an autologous donation program. Four hundred milliliters of blood was collected within 15 min at 34 and 35 weeks of gestation. Continuous electric recordings of fetal heart rate were performed during the first blood collection, and the maternal uterine artery (UtA), umbilical artery (UmA) and fetal middle cerebral artery (MCA) Doppler velocity waveforms were recorded before, immediately after and 24 h after the second collection in each patient. The average fetal heart rate, maternal UtA and UmA pulsatility indices did not change measurably during or after maternal blood collections. However, the average fetal MCA pulsatility index decreased significantly 24 h after maternal blood loss. The observation of a decrease in fetal MCA pulsatility index may indicate delayed fetal asphyxia following mild maternal hemorrhage.

Accuracy of computerized detection of fetal heart rate patterns

Objective: To measure the agreement of computerized detection of fetal heart rate (FHR) patterns with a panel of clinical experts. Method: Digital signal processing techniques and algorithms were used to measure the FHR features of baseline, variability, accelerations and decelerations. Five obstetricians used proprietary software to review, measure, and label the FHR recordings from 41.8 hours of normal and abnormal examples. A composite opinion was defined based on agreement by a majority (3/5) of the experts. Each individual and the computer were compared with the composite. Results: The following table shows the number of hours spent in baseline or nonbaseline (acceleration or deceleration) according to the composite, the portion of this time correctly labeled by the computer-based method and the range of correct detection by individual doctors. FHR State Hours Percentage by Computer Lowest percentage by MD Highest percentage by MD Baseline 26.7 86.5 90.2 96.4 Nonbaseline 15.1 91.0 89.0 96.5 Total 41.8 88.2 89.3 96.5 Conclusions: These physicians were fairly consistent in identifying fetal heart rate features. The performance of the computer was close to the five experts. Further enhancements to the software should bring the performance to the 90% level. It is now possible to study large numbers of tracings and to quantify the association of FHR patterns with newborn status and cord blood gas results.

The prediction and prevention of intrapartum fetal asphyxia in term pregnancies

Objective: This study was undertaken to examine the roles of clinical risk scoring, electronic fetal heart rate monitoring, and fetal blood gas and acid-base assessment in the prediction and prevention of intrapartum fetal asphyxia in term pregnancies. Study Design: The outcomes of 166 term pregnancies with biochemically confirmed fetal asphyxia (umbilical artery base deficit at delivery, >12 mmol/L) were examined. This population included 83 pregnancies delivered abdominally matched with 83 pregnancies delivered vaginally. Antepartum and intrapartum clinical risk factors and neonatal complications were documented. Fetal assessments included fetal heart rate patterns in the fetal heart rate record and fetal capillary blood gas and acid-base assessments. Fetal asphyxia was classified as mild, moderate, or severe on the basis of umbilical artery base deficit (cutoff >12 mmol/L) and neonatal encephalopathy and other organ system complications. Results: Fetal asphyxial exposures were as follows: mild, 140; moderate, 22; and severe, 4. Intervention and delivery during the first or second stage of labor occurred in 98 of the 166 pregnancies. Predictive fetal heart rate patterns were the primary indication leading to intervention and delivery during the first or second stage of labor. Clinical risk factors when present were secondary indications in the clinical decision to intervene. Fetal blood gas and acid-base assessment was a useful supplementary test in 41 pregnancies. Intervention and delivery may have prevented the progression of mild asphyxia in 78 pregnancies and may have modified the degree of moderate or severe asphyxia in 20 pregnancies. Conclusion: Although fetal heart rate patterns will not discriminate all asphyxial exposures, continuous fetal heart rate monitoring supplemented by fetal blood gas and acid-base assessment can be a useful fetal assessment paradigm for intrapartum fetal asphyxia. Such an assessment paradigm will not prevent all cases of moderate or severe fetal asphyxia. However, prediction and diagnosis with intervention and delivery during the first or second stage of labor could prevent the progression of mild asphyxia to moderate or severe asphyxia in some cases. (Am J Obstet Gynecol 2001;184:724-30.)