Routine fetal heart rate monitoring in the antepartum period

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.

Admission cardiotocography: Its role in predicting foetal outcome in high-risk obstetric patients

BACKGROUND

Routine and continuous electronic monitoring of foetal heart rate (FHR) in labour has become an established obstetric practice in high-risk pregnancies in industrialised countries. However, the same may not be possible in non-industrialised countries where antenatal care is inadequate with a large number of high-risk pregnancies being delivered in crowded settings and inadequate health care provider to patient ratios.

AIMS

The objective of this study was to evaluate the predictive value of the admission cardiotocogram (CTG) in detecting foetal hypoxia at the time of admission in labour and to correlate the results of the admission CTG with the perinatal outcome in high-risk obstetric cases.

METHOD

This was a prospective observational study conducted in the labour and maternity ward of a hospital in Gangtok, India, during the period 2008 to 2010. The study included high-risk pregnant women, admitted via the emergency or outpatient department with a period of gestation ≥36 weeks, in first stage of labour with foetus in the cephalic presentation. All women were subjected to an admission CTG, which included a 20 minute recording of FHR and uterine contractions.

RESULTS

One hundred and sixty patients were recruited. The majority of women were primigravida in the 21-30 years age group. About 42% patients were postdated pregnancy followed by pregnancy-induced hypertension (PIH) (15.6%) and premature rupture of membranes (PROM) (11.3%) as the major risk factors. The admission CTG were 'reactive' in 77%, 'equivocal' in 14.4% and 'ominous' in 8.7% women. Incidence of foetal distress, moderate-thick meconium stained liquor and neonatal intensive care unit (NICU) admission was significantly more frequent among patients with ominous test results compared with equivocal or reactive test results on admission. Incidence of vaginal delivery was more common when the test was reactive.

CONCLUSION

The admission CTG appears to be a simple non-invasive test that can serve as a screening tool in 'triaging' foetuses of high-risk obstetric patients in non-industrialised countries with a heavy workload and limited resources.

Antenatal fetal surveillance

PURPOSE OF REVIEW

Antenatal fetal surveillance is a field of increasing importance in modern obstetrics, especially as results in perinatal care have recently made dramatic progress. It is an evolving field, and it is no longer acceptable just to wait and see when problems arise in pregnancy. During the past few decades many studies have shown that antenatal surveillance in unselected populations is of little value. However, high-risk patients benefit from antenatal fetal surveillance, especially women with pregnancy problems associated with intrauterine growth restriction.

RECENT FINDINGS

This review shows that modern antenatal fetal surveillance is based on fetal heart rate monitoring, ultrasound biometry and amniotic fluid assessment, Doppler blood flow studies of fetal and uteroplacental circulation, and an evaluation of biophysical fetal parameters.

SUMMARY

Used in combination these methods lead to improvements in fetal morbidity and mortality. The aim of future research should be to minimize the risks of fetal morbidity and mortality further by the optimal timing of delivery. Better organization of healthcare systems may improve our ability to identify at-risk patients during pregnancy. There is potential to improve the specificity of fetal surveillance tests, e.g. better methods of biometry and amniotic volume estimation with three-dimensional ultrasound and measurements of subcutaneous tissue. Improved knowledge of fetal physiology can be gained from research on fetal circulation with Doppler studies. Computer analysis of the fetal heart rate can increase the specificity of that test, and artificial neural networks may enhance the ability to evaluate the optimal use of integrated testing.

The relationship of maternal position to the results of brief nonstress tests: a randomized clinical trial

OBJECTIVE

This study was undertaken to determine whether maternal posture (left lateral recumbent vs semi-Fowler position) had any effect on nonstress test results when the test was performed for a shortened period (10 minutes).

STUDY DESIGN

In this randomized clinical trial of 108 patients with singleton pregnancies at 32 to 42 weeks' gestation, patients were randomly assigned to a "sitting first" (semi-Fowler position) or a "supine first" (left lateral recumbent position) group at the initial visit. The order of position was alternated at subsequent visits. Ten minutes of fetal heart rate monitoring was performed in each position at each visit. Computer analysis of the nonstress test was used to interpret each 10-minute segment for reactivity. Statistical analyses were performed on the paired nonstress test unit (sitting and supine).

RESULTS

There were no adverse clinical outcomes among the participants. Logistic regression analysis showed that both the sequence of the nonstress test and the position were significant and independent factors related to nonstress test reactivity. Tests performed during the second 10 minutes and tests performed with the patient in the semi-Fowler position were more likely to have reactive results.

CONCLUSION

The semi-Fowler position is a superior position for conducting a nonstress test in a short period. Use of this position could decrease the need for prolonged monitoring, thus leading to a more time-effective evaluation of patients at risk.

Nonstress testing and contraction stress testing

Antepartum fetal heart rate (FHR) testing, including the nonstress test and contraction stress test, has evolved in clinical usage over the past 3 decades. Although the nonstress test has become a standard of care in high-risk pregnancy, it has been modified by the use of fetal stimulation (vibroacoustic stimulation) and the addition of automated fetal movement recording (actocardiotocography). In all of its formats, antepartum FHR testing has been associated with reduction of preventable fetal loss. More recently, there have been attempts to improve test efficacy by computer-enhanced approaches.

Semi-Fowler's positioning, lateral tilts, and their effects on nonstress tests

OBJECTIVE

To determine whether a lateral tilt for women in semi-Fowler's position for antepartum nonstress tests (NSTs) (a) promotes NST reactivity or (b) shortens testing time required to obtain a reactive tracing.

SETTING

An antepartum fetal assessment unit of a tertiary care facility in eastern Canada.

DESIGN

In this prospective, randomized study, a computer analysis of the NSTs was used to obtain an objective, standardized interpretation of fetal heart rate reactivity. Participants were randomly assigned to two experimental groups using semi-Fowler's position with a 45-degree tilt to either the left or right, or to a control group using semi-Fowler's position with no lateral tilt.

PARTICIPANTS

A convenience sample of 823 nonstress tests was obtained from women with singleton pregnancies, intact amniotic membranes, and gestations between 32 and 42 weeks. The final sample available for analysis totaled 738 nonstress tests from 573 pregnancies.

MAIN OUTCOME MEASURES

Percentage of reactive nonstress tests and the number of minutes required for tests to be reactive.

RESULTS

The rate of reactive NSTs and the time to achieve a reactive NST did not differ statistically for any of the three study groups. Likewise, NST outcomes were similar when the left-tilt group was compared with the right-tilt group. Although no significant differences were found between study groups, less than 2% of the women in the control group (semi-Fowler's position without a lateral tilt) experienced symptoms consistent with supine hypotensive syndrome.

CONCLUSIONS

No statistically or clinically significant differences were found in nonstress tests between the three groups. Lateral tilting did not shorten test time. Results do suggest that hemodynamic changes can occur in 3rd trimester women who are in semi-Fowler's position without a lateral tilt. Lateral tilting of gravidas in semi-Fowler's position during nonstress testing is thus supported to avoid hypotensive symptoms.

Use of cordocentesis in the management of preterm or growth-restricted fetuses with abnormal monitoring

The dilemma of when to deliver preterm or growth-restricted fetuses with abnormal monitoring is faced by all those treating such patients. Current noninvasive tests for fetal well-being have relatively high false-positive rates. Cordocentesis allows the clinician to directly analyze fetal blood and determine whether the fetus is truly in distress, is suffering from aneuploidy, or is plagued by infection. However, with improved neonatal care, otherwise normal infants of birth weight greater than 1500 gm have very low morbidity and mortality rates and any delay in delivery offered by cordocentesis is probably not justified. It is in the fetus whose estimated weight is below 1500 gm that cordocentesis should be used. If the results are normal, expectant management and the administration of corticosteroids will allow for pulmonary maturation and a more favorable outcome.

The value of Doppler ultrasonography in prolonged pregnancies

One hundred forty-two gravid women at term were followed prospectively by a non-stress test, estimation of amniotic fluid volume and Doppler velocimetry of the umbilical and uterine arteries. Adverse perinatal outcome was detected in 12 women (8.5%). Abnormal antepartum tests were detected in 26 women (17%). Seven women had an abnormally elevated resistance index (RI) in the umbilical artery; but only two had an abnormal outcome. Seven women had an abnormally elevated RI in the uterine artery, but only two had abnormal outcome. Three out of 11 women with oligohydramnion had abnormal perinatal outcome. Only one out of seven women with an abnormal non-stress test had abnormal perinatal outcome. In six women, more than one antepartum test was abnormal. The various surveillance methods demonstrated a low sensitivity (the highest was obtained by estimating amniotic fluid volume: 25%) and a low positive predictive value (the highest obtained by measuring the resistance index in either the umbilical or the uterine arteries: 28.6%). By considering any abnormal test as a positive test result for a given patient, a substantial improvement in sensitivity (66.7%) and positive predictive value (33.3%) are obtained. Doppler velocimetry adds very little in itself to the follow-up of patients with post-term gestations. However, when combined with additional antepartum tests, it may increase our ability to predict the compromised fetus in this condition.

The predictive value of fetal heart rate monitoring: a retrospective analysis of 2165 high-risk pregnancies

The predictive value of fetal heart-rate monitoring on fetal well-being was studied in 2165 high-risk pregnancies. 1883 reactive nonstress test (NST) patterns and 278 nonreactive NST patterns and 4 cases of sinusoidal pattern were obtained. Oxytocin challenge test (OCT) was applied to 263 nonreactive cases. OCT was not applied to 15 cases out of 278 nonreactive NST cases, because of placenta previa, abruptio placenta and previous cesarean section. There were 155 cases with negative OCT, 84 cases with positive OCT and 24 cases with equivocal, prolonged or severe variable decelerations. Sensitivity and specificity were for NST 50 and 88% and for OCT 60 and 67%. The positive and negative predictive values were 11 and 98% for NST and 18 and 93% for OCT. It is concluded that the reactive nonstress test is a reliable test for good outcome but a positive oxytocin challenge test is not a reliable test for poor outcome. Additional procedures are necessary such as assessment of fetal growth, doppler velocity waveforms and fetal biophysical profile to avoid unnecessary obstetric interventions and to reach good fetal outcome.

Maternal perception of decreased fetal movement as an indication for antepartum testing in a low-risk population

Maternal perception of decreased fetal movement has traditionally been used as an indication for fetal testing in high-risk patients. Two hundred ninety-two low-risk patients who presented with a complaint of decreased fetal movement were studied to determine the incidence of adverse outcome and need for further testing. Initial testing included a nonstress test and ultrasonographic examination. Five (1.7%) of the study group had fetal death on initial examination and 4.4% of patients required immediate delivery because of abnormal maternal or fetal evaluation. An additional 5.8% had abnormal fetal heart rate tracings that necessitated follow-up. Fifty-two percent of patients with normal initial evaluations underwent additional testing. There were no significant differences between patients undergoing additional testing, patients having no additional testing, and a low-risk nontested group with regard to adverse outcome. Fetal surveillance is indicated in low-risk patients with decreased fetal movement. Additional testing of patients with a normal initial evaluation and no further complaint of decreased fetal movement may not be necessary.

Fetal well-being: nonimaging assessment and the biophysical profile

All of the testing methods described above are very good at predicting continued fetal health when test results are reassuring. Each test also suffers from a very poor ability to predict compromise when results are abnormal. Thus, the primary value of antepartum fetal monitoring is in identifying those pregnancies that do not require immediate intervention and may be allowed to continue. Certainly, all pregnant women (regardless of risk status) should monitor fetal movement as part of their fetal surveillance. For patients at risk, a variety of testing schemes are available using combinations of the NST, CST and BPP. There are several reasons for using the NST as the primary testing method for those at risk. Even a small antenatal testing area can accommodate three or four FHR monitors, and a single antenatal testing nurse can perform several NSTs at a time. Because the BPP requires an ultrasound machine and a trained technician to perform, and because only one BPP can be done at a time, many obstetricians who do their own in-office fetal testing are unable to adopt BPP testing as their primary means of surveillance. Additionally, it is more economical to use the NST than the BPP for first-line testing. Assuming charges of $150 and $300 for the NST and BPP, respectively, and assuming that 20% of NSTs are nonreactive and require a BPP for second-line testing, the weekly cost of testing 100 patients is $21,000 for the NST and $37,500 for the BPP. This increase-in-testing cost must be balanced against the small improvement in perinatal mortality rates achieved with the use of the BPP. Because it must be performed in a hospital setting and takes an average of 90 minutes to complete, the CST is more expensive and time-consuming than either the NST or BPP and it is less frequently used as the primary method of fetal testing. In the past the CST was the most commonly used secondary test after a nonreactive NST, but use of the BPP in this situation has now become commonplace. Although the CST still has an important role in fetal testing, the BPP is better suited for use in this setting because of its technical ease and low incidence of abnormal results. Thus, many centers use the NST as the primary mode of testing for the fetus at risk, often with a sonographic assessment of AFV.(ABSTRACT TRUNCATED AT 400 WORDS)

Umbilical cord acid base changes associated with perinatal cardiac failure

Two infants delivered by emergency cesarean section because of fetal distress are described, and the umbilical blood acid-base findings are discussed. One fetus was stillborn, the other died in the immediate neonatal period, and both showed signs of cardiac dilation and failure on postmortem examination. Umbilical cord blood gas determination at the time of delivery showed almost normal values of pH, PcO2, and PO2 in the umbilical vein but acidotic pH with high PCO2 and low PO2 values in the umbilical artery samples. These findings are probably the result of a prolonged umbilical blood circulation time because of fetal cardiac failure. This sluggish perfusion allows the equilibration of fetal blood with maternal intervillous blood, and the findings in the fetal umbilical vein approximate maternal uterine venous values. Umbilical cord acid-base determinations in perinatal surveillance are commonly recommended without specific details. Umbilical artery samples must be obtained to properly assess the metabolic status of the fetus at the time of birth.

Fifteen years of experience with antepartum fetal testing

The introduction of antepartum fetal heart rate testing occurred in the very early 1970s. This article describes the evolution of testing within the Los Angeles County/University of Southern California Medical Center and encompasses a 15-year time period between 1971 and 1985. During this time approximately 200,000 patients were delivered of their infants. Fetal surveillance increased from less than 1% to current levels of 16% of patients. The antepartum fetal death rate was evaluated as a measure of evaluating the usefulness of antepartum testing. The fetal death rate after antepartum testing in selected high-risk patients was significantly less than that found in those patients not tested. The questions that might be raised regarding broader application of this technique and potential benefits are stated.

Antepartum cardiotocography

Antepartum cardiotocography remains a valuable adjunct in the management of the high-risk gravida. Twice weekly use of NST coupled with real-time ultrasound assessment of amniotic fluid volume appear reasonable approaches to testing. More controversial is the use of testing in all pregnancies. Clearly, if one could reduce the perinatal mortality to 1-2/1000, such universal application of testing could be justified. However, more pragmatic concerns, such as personnel and cost constraints have all but prohibited the adoption of this policy. Secondly, in an attempt to improve the predictive reliability of antenatal testing additional evaluation of patients demonstrating diminished AFV or variable decelerations should be considered. More frequent testing or consideration for delivery are reasonable management plans. Finally, the use of acoustic stimulation to reduce the frequency of persistently non-reactive NSTs offers considerable promise. Investigations in this and other techniques of surveillance are ongoing. The best single method remains to be discovered, but utilization of current techniques offers the obstetrician a reliable technique by which to assess fetal well-being.

Antepartum nonstress fetal heart rate monitoring: systematic analysis of baseline patterns and decelerations as an adjunct to reactivity in the prediction of fetal risks

A total of 1552 antepartum nonstress tests performed during the week before delivery are analyzed with respect to both reactivity and the presence of pathologic baseline patterns (tachycardia, bradycardia, diminished beat-to-beat variability) or decelerations. Correlation with mode of delivery and condition of the newborn infant shows that, irrespective of nonstress test reactivity, the presence of baseline anomalies and/or decelerations is associated with significantly increased perinatal morbidity and mortality. Nonstress test analysis, if systematic, that is, not restricted to reactivity alone, makes it possible to better detect fetuses at high perinatal risk, in which case closer surveillance would be indicated.

The nonstress test as a diagnostic test: a critical reappraisal

In the past decade the nonstress test has become a major method of assessing high-risk pregnancy. Although many studies have been published, there has been a lack of rigorous adherence to the standard criteria for diagnostic testing, that is, presentation of test specificity, sensitivity, predictive value, and the prevalence of abnormal outcomes in the populations studied. Furthermore, the populations studied vary widely in composition, testing conditions, methods of test interpretation, and clinical management. The authors undertake a review of these studies, with a focus on these issues, in an attempt to indicate potential problems involved in current test usage and to suggest avenues for needed clinical investigation.

Fetal assessment based on fetal biophysical profile scoring: experience in 12,620 referred high-risk pregnancies. I. Perinatal mortality by frequency and etiology

Fetal biophysical profile scoring was used as a method for antepartum fetal risk assessment in 12,620 high-risk patients referred in a 55-month interval. A total of 26,257 tests were performed on these patients (range, one to 18 tests per patient). Ninety-three perinatal deaths occurred (gross perinatal mortality rate, 7.37 per 1000) of which 62 (66.6%) were due to a major anomaly, seven were due to Rh disease (7.5%), and the remaining 24 deaths (25.8%) occurred in structurally normal fetuses. The corrected perinatal mortality rate was 1.90 per 1000. Eight structurally normal fetuses died within 1 week of a normal test result (corrected false negative rate, 0.634 per 1000). These data suggest fetal biophysical profile scoring is an accurate method for identification of the fetus at risk for perinatal death.

A randomized trial of weekly cardiotocography in high-risk obstetric patients

A randomized clinical trial of once-weekly antenatal fetal heart rate monitoring in 539 high-risk patients could find no benefit of monitoring in terms of perinatal mortality, morbidity or Apgar score. The previously well-documented association between abnormal antenatal fetal heart rate traces and low Apgar score was confirmed. A detailed case review showed that in this population monitoring was irrelevant to almost all of the 13 perinatal deaths.

Comparison of antepartum testing schemes for the management of the postdate pregnancy

We analyzed the outcome results of 583 postdate pregnancies managed prospectively by one of three antepartum testing schemes, each predicated on the nonstress test. In scheme 1, we relied upon the contraction stress test for evaluation of the nonreactive nonstress test. In scheme 2, we used a modified biophysical profile to evaluate the nonreactive nonstress test. In addition, patients were tested semiweekly. In scheme 3, we added routine weekly ultrasound evaluation of amniotic fluid volume to scheme 2. Only in scheme 3 did we induce labor for decreased amniotic fluid volume or fetal cardiac decelerations irrespective of reactivity. The incidence of fetal distress, perinatal mortality, and perinatal morbidity was increased in babies with decelerations or decreased amniotic fluid volume. Nevertheless, outcome results in scheme 2 were improved over those with scheme 1 and were best with scheme 3. These results suggest a benefit to both semiweekly testing and liberalized criteria for intervention in postdate pregnancies. We also compared the outcome results of scheme 3 with those reported for schemes in which the weekly contraction stress test was used as the primary form of surveillance. We found the outcome results comparable in that both schemes showed minimal mortality and morbidity statistics but high intervention rates (25% to 30%). Differences in methodology and test criteria, however, make such comparisons less than ideal.

Fetal heart rate accelerations and late decelerations during the course of intrauterine death in chronically catheterized rhesus monkeys

The appearance of late decelerations and the disappearance of accelerations in the fetal heart rate were observed during the days that preceded intrauterine fetal death in nine chronically instrumented rhesus monkeys. All nine animals had recovered satisfactorily from the initial surgical procedure, as evidenced by normal biophysical and biochemical parameters. After recovery, all the fetuses had shown accelerations and no late decelerations with spontaneous uterine contractions. The mean duration of the preparations was 16.1 days. The duration of the preterminal observation period varied from 3 to 13 days, during which time no experiments were performed. The fetuses died during labor at a mean gestational age of 143 days. Late decelerations were the first sign of fetal deterioration and occurred with a slight but significant decrease in fetal PaO2 without changes in pH, whereas accelerations in fetal heart rate were still present. The loss of accelerations in fetal heart rate was a later phenomenon and was associated with significant reductions in fetal pH and PaO2.

The value of antenatal cardiotocography in the management of high-risk pregnancy: a randomized controlled trial

The value of routine regular antenatal cardiotocography (CTG) in the management of high-risk pregnancy was assessed in a prospective randomized controlled study of 353 patients. All patients had a weekly CTG trace during the last 6 weeks of pregnancy and according to the random allocation the tracings were concealed from, or available to, the clinicians. Other methods of assessing fetal welfare were available to both groups. There was no significant difference between the concealed and revealed groups in the timing and mode of delivery, birthweights, Apgar score and neonatal morbidity. No apparent effect from the routine use of antenatal CTG in high-risk pregnancy was shown.

A randomized controlled trial of non-stress antepartum cardiotocography

In a prospective randomized controlled study of non-stress antepartum cardiotocography (CTG), involving 569 tracings in 300 patients, "non-reactive' traces showed a significant association with still-births and neonatal deaths, intrauterine growth retardation, admission to special care baby unit for conditions associated with intrauterine hypoxia, and low Apgar scores at 1 and 5 min. The report of the CTG was made available to the clinician in 144 patients and withheld in 156 patients. With the report available, significantly more patients were allowed to continue their antenatal care as out-patients, and significantly more antenatal in-patients were allowed home. There were no other significant differences in management, or outcome in the two groups.

Trauma in the pregnant patient

The tragedy of major trauma to the pregnant woman presents the dilemma of managing two lives. An understanding of the pregnant patient's altered response to trauma and attention to detail in applying appropriate diagnostic tests will help to guarantee a successful outcome. Liberal use of consultation is suggested for medical and legal reasons. Obstetric consultation is highly recommended to document pregnancy and to assist in assessing fetal well-being. The obstetrician can perhaps provide reassurance to the mother and the family by demonstrating fetal heart tones with the Doppler instrument and can then further provide the necessary counseling and follow-up regardless of the outcome of the pregnancy. The pregnant patient with significant trauma should be closely observed and records carefully documented. Patients with minor injuries usually do not require admission, whereas more significant injuries require longer periods of observation. Admission criteria include vaginal bleeding, uterine irritability, abdominal tenderness or pain, evidence of hypovolemia, a change in or absence of fetal heart tones, or leakage of amniotic fluid. Management should primarily be directed toward guaranteeing the health of the mother, which better insures the health of the fetus.

Fetal acceleration test

Five hundred thirty-one fetal acceleration tests were performed on 112 normal subjects at various gestational ages ranging from 22 and 41 weeks. Analysis of the results revealed that the frequency of nonreactive tests was directly related to gestational age, ranging from 56% in the 22- to 25-week group to 6% in the 38- to 41-week group. During the same period 919 fetal acceleration tests were performed on 339 high-risk subjects. When these were divided into groups by gestational age, the frequency of nonreactive tests did not differ significantly from that in the normal group of subjects. These dats suggest three possible conclusions: (1) that the high frequency of false positive results does not justify the performance of utilization of such tests before 30 weeks' gestational age; (2) that nonreactivity is probably a function of gestational age rather than an indication of fetal jeopardy; (3) that the frequency of "false positive" tests among the normal population may invalidate reliance on such tests for management of subjects in a high-risk category.

A new modality in nonstress testing: evaluation of beat-to-beat fetal heart rate variability

Fetal monitoring equipment that provided accurate external measurement of the interval between each fetal heartbeat permitted the evaluation of beat-to-beat fetal heart rate (FHR) variability as part of routine nonstress testing. Nonstress tests (NSTs) were performed on 350 high-risk patients over a 12-month period. The beat-to-beat FHR variability and the reactivity of the last NST within 7 days of labor were analyzed in relation to the appearance of fetal distress during labor as indicated by late decelerations. Beat-to-beat FHR variability combined with nonstress testing was more predictive of subsequent fetal distress than nonstress testing alone. In all instances, complete loss of beat-to-beat FHR was followed by fetal distress during labor. Fetal distress was present in only 39% of labors following nonreactive NSTs. The inclusion of beat-to-beat FHR variability in nonstress testing can significantly aid in the detection of fetal compromise.

The role of real-time scanning in antenatal fetal surveillance

The additional value of real-time ultrasound scanning (RTBS) in antepartum assessment of fetal well-being was studied in 158 high-risk patients after a nonstress test (NST). Fetal breathing movements (FBM), fetal movements (FM), tonus (TON), and normal amniotic fluid volume (AFV) when present on RTBS were reliable signs of fetal well-being. These ultrasound markers of fetal well-being appeared to be as reliable indicators of good outcome as the reactive NST. Multiple indicators did not improve the accuracy of the prediction of normal outcome. All test results were normal in only about 50% of patients. In general, abnormal test results were poor indicators of poor outcome. Only when all parameters were abnormal were babies invariably affected. Five of six babies with major anomalies showed increased AFV, and seven of 13 growth-retarded or postmature babies demonstrated decreased AFV. The parameters obtained on RTBS appeared to be far more reliable than the contraction stress test (CST) in discriminating the truly abnormal fetus. Three babies with positive CST in this study had normal outcomes. These results, if confirmed in larger studies, suggest that RTBS after a nonreactive NST is an effective and potentially economical method of fetal assessment.

The nonstress test: a review of 3,000 tests

For the antepartum evaluation of fetal well-being in the high-risk pregnancy, the nonstress test (NST) has been found to be clinically efficacious. The basis for its interpretation has been the presence (reactive or normal) or absence (nonreactive or abnormal) of fetal heart rate accelerations in response to fetal activity. If a nonreactive NST was encountered, the fetus was evaluated further with the contraction stress test (CST). Between July 5, 1977, and October 20, 1979, 3,000 NSTs were performed on 1,452 women with high-risk pregnancies. The NST interpretations were reactive (85.4%), nonreactive (14.0%), and unsatisfactory (0.6%). While the reactive group experienced a favorable fetal outcome, the nonreactive group demonstrated a significant increase in the overall cesarean section rate, the rate of cesarean sections for fetal distress, and the perinatal mortality rate. Based on our experience, the NST continues to be a valuable procedure for the assessment of fetal well-being in our high-risk pregnancies.