Fetal acceleration test

Antepartum Fetal Surveillance: ACOG Practice Bulletin, Number 229

The goal of antepartum fetal surveillance is to reduce the risk of stillbirth. Antepartum fetal surveillance techniques based on assessment of fetal heart rate (FHR) patterns have been in clinical use for almost four decades and are used along with real-time ultrasonography and umbilical artery Doppler velocimetry to evaluate fetal well-being. Antepartum fetal surveillance techniques are routinely used to assess the risk of fetal death in pregnancies complicated by preexisting maternal conditions (eg, diabetes mellitus) as well as those in which complications have developed (eg, fetal growth restriction). The purpose of this document is to provide a review of the current indications for and techniques of antepartum fetal surveillance and outline management guidelines for antepartum fetal surveillance that are consistent with the best scientific evidence.

Factors that increase reactivity during fetal nonstress testing

PURPOSE OF REVIEW

The most common method of antepartum fetal surveillance is the nonstress test (NST). Although it has satisfactory false-negative rates, dubious nonreactive results may challenge the physician. Any method or factor increasing the reactive NST results or shortening the time to attain a reactive test may be considerably useful.

RECENT FINDINGS

Most of the studies have found no effect of maternal glucose administration on fetal heart rate and fetal activity, specificity of NST, time to reactivity and percentage of reactive NST results when compared with the control group. Maternal intake of 70% cocoa or caffeine had stimulating action on the fetal reactivity, and this effect on the fetal heart rate was more marked with high concentrations of cocoa (80%). Studies on maternal positioning during NST had equivocal results. Fetal manipulation has no impact on the NST reactivity. Vibroacoustic and halogen light stimulation may be associated with a reduction in time to reactivity.

SUMMARY

These methods may increase the reactivity during a NST and may facilitate the antenatal fetal surveillance.

Identification, assessment and management of fetal compromise

The main goals of fetal surveillance are to avoid fetal death and to recognize the fetus that will benefit from early intervention with resuscitation or delivery. Surveillance can occur in the antepartum or intrapartum period. Continuous fetal heart rate monitoring is the most common form of surveillance in the intrapartum period. Several techniques are used in the antepartum period, including nonstress test, biophysical profile, and contraction stress test. Multiple techniques are used once distress is noted in the fetus, with the ultimate resuscitation effort being delivery.

Correlation between fetal heart rate reactivity and mortality and severe neurological morbidity in extremely low birth weight infants

OBJECTIVE

To determine the correlation between specific fetal heart rate (FHR) abnormalities and the incidence of death, severe (grade 3-4) intraventricular hemorrhage (IVH) and periventricular echogenicity (PVE) in extremely low birth weight infants (ELBW) within the first 4 days after birth.

METHODS

The study included live-born ELBW infants ≤ 30 weeks' gestation who were born in 2000-2007 at Kaplan Medical Center, Rehovot, Israel, and, who had FHR monitoring during the 24 h before delivery and cranial ultrasound during the first 4 days of life. FHR pattern was analyzed for the presence of baseline rate, reactivity, variability and decelerations.

RESULTS

96 infants with mean birth weight 757 ± 150 g and mean gestational age 25.8 ± 1.5 weeks were included. By 4 days of life, 23/96 (24%) died, 17/96 (18%) developed severe IVH and 31/96 (32%) had PVE. Absence of reactivity was significantly associated with increase in both death (p = 0.02, OR 3.45, 95% CI: 1.22-9.47 and severe IVH (p = 0.029, OR 3.33, 95% CI: 1.25-10) but not with PVE. Other FHR parameters were not associated with adverse outcome.

CONCLUSION

These results suggest that FHR reactivity may be of value in predicting short-term outcome in ELBW infants. This may be helpful in counseling parents with imminent extremely preterm birth.

Fetal assessment during pregnancy

Fetal monitoring during pregnancy is used to prevent fetal death. This article addresses the goals of fetal monitoring during pregnancy. Methods of fetal surveillance are reviewed, as well as the meaning of abnormal fetal testing and how these results relate to fetal and neonatal outcome. Overall, pediatricians who understand the goals, methods, and interpretation of fetal testing can communicate more effectively with the delivering obstetric team in anticipation of optimizing obstetric and pediatric outcomes.

On intrapartum fetal monitoring

The currently advised conduct for intrapartum surveillance of the fetus is either intermittent auscultation of continuous electronic monitoring, depending on the physician's preference. This applies to all, normal or high-risk, conditions. The bases for this recommendation, a number of controlled studies comparing the two methods, showed no better neonatal outcomes and increased cesarean section rates with electronic fetal monitoring. A review of the works pertaining to fetal development of cardiovascular and central nervous systems and their response to various pathophysiologic conditions (in animals and humans) was carried out in an effort to find an explanation for this apparently uncongruous position. It was found that fetal responses to seemingly comparable conditions are radically different depending on age of gestation. Many authors have pointed this out for the human fetus. However, for interpretation of electronic fetal monitoring in labor, various standard, nondescriptive, confusing words are used to imply the need for rapid intervention. The complete lack of uniform interpretation has been shown in studies comparing interobserver and intraobserver variations. This may be the consequence of poor or superficial teaching of a tool that requires much study and hard work for useful application. The inescapable conclusion is unpleasant but inevitable: to use electronic fetal monitoring properly it is necessary to start a new learning of the physiology of the fetus, its changing evolution as pregnancy advances, its different responses under stress or distress, and the various ways these are represented in electronic fetal monitoring tracings. These efforts take dedication and time spent in labor suites collating tracings with neonatal condition. Only by doing this will it be possible to assist the laboring patients with a useful tool that, so far, has not been adequately applied because of insufficient understanding.

Predictive value of a fetal heart rate acceleration at the time of fetal blood sampling in labour

It has been suggested that the fetal heart rate response to fetal stimulation in labour is an indication of fetal condition. This study was designed to evaluate scalp stimulation at the time of fetal blood sampling. All labours requiring fetal scalp pH measurement during one year at the John Radcliffe Maternity Hospital were reviewed to determine the association between pH result and the fetal heart rate response to the first scalp blood sample. Sixty-nine (50%) cases showed an acceleration and none had a scalp blood pH less than 7.20. Six (8.7%) of the cases which did not show an acceleration of the fetal heart rate had a pH less than 7.20 and this group had a greater incidence of analgesia usage and twice as many caesarean sections (39%). The detection rate for non-acidaemia using a fetal heart rate acceleration at the time of fetal blood sampling was 52 percent but the specificity and positive predictive value were both 100 percent. The false negative rate was 91 percent. Thus, whilst an acceleration was reassuring, the absence of an acceleration at the time of fetal blood sampling was not a good predictor of fetal acidaemia. These results are compared with the data from four other published reports.

The preterm nonstress test: effects of gestational age and length of study

The application of the nonstress test between 24 and 32 weeks' gestation has been limited by high rates of "false" nonreactivity in normal fetuses, by use of term criteria, and the lack of age-appropriate interpretative standards. To establish such standards, we studied 30 normal fetuses undergoing 90-minute fetal heart rate recordings at 2-week intervals from 24 to 32 weeks' gestational age. Using a specially programmed computer we quantified (1) baseline fetal heart rate, (2) incidence of 10- and 15-beat accelerations, and (3) incidence of fetal heart rate decelerations. With a criterion of three 15-beat accelerations per 30 minutes 91% of tests were reactive within 90 minutes. A criterion of three 10-beat accelerations per 30 minutes was associated with 100% reactivity within 60 minutes. Suitable interpretative criteria may be established for nonstress tests before 32 weeks' gestation by extending the testing time or by decreasing the minimum amplitude required of fetal heart rate accelerations.

Current concepts in management of obstetric problems for pediatricians. I. Monitoring the high-risk fetus

Modern pediatric/neonatal practice demands an understanding of fetal monitoring. Biochemical techniques have given way to biophysical and ultrasonographic modalities in an attempt to improve both sensitivity and specificity. Simple techniques such as fetal movement counts show promise and are being investigated.

The relationship between antepartum fetal heart rate, intrapartum fetal heart rate, and fetal acid-base status

The relationships between antepartum baseline fetal heart rate, baseline variability, accelerations, decelerations, and fetal movement and intrapartum fetal heart rate, fetal acid-base assessment at delivery, and Apgar scores 1 and 5 minutes after delivery were studied in 290 mature pregnancies. There was a significant relationship between antepartum and intrapartum baseline fetal heart rate and baseline variability. There was no relationship between antepartum and intrapartum accelerations or decelerations. There was no correlation between antepartum fetal heart rate or fetal movement and fetal acid-base status at delivery or Apgar scores 1 and 5 minutes after delivery. There was a trend for decreased accelerations and decreased fetal movements to be associated with a low Apgar score 1 minute after delivery.

A prospective analysis of the influence of gestational age on the baseline fetal heart rate and reactivity in a low-risk population

The nonstress test is of recognized value for the antepartum assessment of fetal well-being. Less well defined, however, is the relationship between baseline fetal heart rate, reactivity, and the gestational age of the fetus. A prospective analysis of the nonstress test in a preterm, low-risk population was begun. Weekly tests were begun as early as 23 weeks and continued to term. A test was considered reactive if there were two or more fetal heart rate accelerations within a 20-minute period. A total of 128 nonstress tests were performed on 25 low-risk patients. Of these tests, 84 (64%) were considered reactive. With advancing gestational age, a progressive increase in the incidence of reactive tests was observed. However, no significant difference in baseline fetal heart rate could be identified between term and preterm fetuses. In addition, the frequency and amount of accelerations and decelerations were determined. Decelerations were not noted more frequently in the preterm population. Conversely, accelerations occurred more frequently with advancing gestational age. The pregnancy outcome was excellent for all study patients. It is concluded, therefore, that with advancing gestational age more reactive nonstress tests are seen. Baseline fetal heart rate and the frequency of decelerations appear to be unaffected by advancing gestational age. Finally, although the numbers are small, the nonstress test appears to be a suitable technique for assessing fetal well-being in the preterm fetus.

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.