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PubMed1989

[The extent of fetal heart rate accelerations associated with fetal body movements in relation to the duration of fetal body movement].

The temporal relations between fetal body movements and associated fetal heart rate accelerations were shown as the ratios of duration of acceleration or acceleration amplitude and the duration of associated fetal body movements in 44 normotrophic and 40 hypotrophic fetuses (body weights within the 6th to 10th percentiles, n = 19, and less than or equal to the 5th percentile, n = 21) between the 36th and 40th gestational weeks. Related to the duration of associated fetal body movements, hypotrophic fetuses proved to have gradually smaller heart rate accelerations than normotrophic fetuses. Moreover, the acceleration parameters duration and amplitude were dependent on the relative duration of fetal body movements. Short fetal body movements were accompanied by fetal heart rate accelerations of relatively highest degree and vice versa. As a consequence, no comparison is possible between temporally different fetal body movements and their associated heart rate accelerations. Of the two acceleration parameters duration and amplitude, the inclusion of the accelerations amplitude in the above mentioned ratio yielded the most obvious results. Taking into consideration that fetuses with intrauterine growth retardation are often in a state of chronic hypoxia, the ratios of acceleration amplitude and durations of associated fetal body movements indicated different degrees of this metabolic situation.

Adult↗
PubMed1986

Fetal heart rate variability changes and fetal behavioural cycles during labour.

In a study of 301 consecutive fetal heart rate (FHR) recordings of greater than or equal to 6 h duration, consecutive episodes of low and high FHR variability consistent with cycles of quiet and active fetal behaviour were found in 38% of spontaneous and 68% of induced labours at term (P less than 0.0001). Quiet periods (episodes of low FHR variability) had durations of 12-93 min (mean 25, SD 11 min) and in 48% of cardiotocographs (CTGs) these episodes had a long-term variability of less than 5 beats/min. The implications of these findings are discussed in relation to the use of FHR recording for intrapartum surveillance.

Behavior↗
PubMed1998

[Prenatal recording of fetal heart action with magnetocardiography].

Fetal magnetocardiography (fMCG) registers the magnetic field generated by the fetal heart. In contrast to the fetal electrocardiogram, fECG permits non-invasive registration of fetal heart activity and documentation of all parts of the PQRST-wave-forms from the second trimenon onwards. This facilitates the determination of cardiac time intervals and establishment of reference values for different stages of pregnancy. We examined 53 women in 104 recordings from the 10th week of gestation onwards (1 to 10 recordings per individual). The fMCG (37 magnetic channels, sampling rate 1024 Hz, bandwidth 1-200 Hz) was recorded non-invasively over the mother's abdomen in a magnetically shielded room. Registration of fetal heart beats was generally successful from the 20/21th week of gestation onwards. In a few cases, fetal heart beats could be registered as early as in the 16th week. Cardiac time intervals and amplitudes of fMCG increased concordantly with fetal growth. Mean P wave duration increased from 31 to 49 ms (p < 0.05), PQ interval from 95 to 107 ms (n.s.) and QRS duration from 36 to 52 ms (p < 0.01). The mean amplitudes of the P and R waves also increased. FMCG, furthermore permits a prenatal diagnosis of fetal cardiac arrhythmias. We recorded fetal arrhythmias in 20 cases (26-38th week), including episodes of ventricular and supraventricular arrhythmias or atrioventricular blockings. Due to its high resolution, fMCG offers new information on the development of fetal cardiac activity which cannot be achieved by conventional methods like cardiotocography or dopplerultrasound. Therefore, fMCG could become a new diagnostic instrument for monitoring fetal wellbeing during pregnancy.

Adult↗
PubMed1986

Relationship of baseline fetal heart rate to gestational age and fetal sex.

A study of 37 patients who underwent 365 antepartum fetal heart rate tests showed a significant difference in heart rate between 19 to 24 weeks' and 36 to 40 weeks' gestation. Baseline heart rate remained within the normal range, suggesting that an abnormal heart rate at any gestational age should prompt further fetal assessment. Baseline fetal heart rate was not significantly different between male and female fetuses.

Female↗
PubMed1980

[Intra-uterine death during monitoring of the fetal heart rate].

Although the fetal heart rate was being monitored in 16 378 patients during labour, intra-uterine death occurred in 13 cases (0,08%). These fetuses had birth weights of more than 1 000 g. In one patient monitoring was discontinued long before delivery, and fetal death occurred when a partially dilated cervix prevented quick delivery of the fetus which presented by the breech. In all the remaining patients an abnormal fetal heart rate pattern preceded intra-uterine death. Fetal death was probably unavoidable in 4 patients, even with monitoring. Abnormal fetal heart rate patterns were recorded in 2 of these, but the fetuses were estimated as being too small to be delivered by caesarean section. However, they weighed 1 160 g and 1 120 g. The 3rd patient had severe fetal bradycardia on admission and intra-uterine death occurred soon afterwards. The 4th patient refused caesarean section for a prolapse of the umbilical cord, and a vacuum extraction was attempted when the cervix was not yet fully dilated. Severe variable decelerations occurred in 5 of the 8 patients in whom intra-uterine death could have been avoided. Severe bradycardia was present in 3 patients immediately before fetal death, but it may have been present in more patients because the fetal heart rate was not recorded in all cases until death had occurred.

Adolescent↗
PubMed1996

Changes in the PR interval--fetal heart rate relationship of the electrocardiogram during fetal compromise in chronically instrumented sheep.

OBJECTIVES: The evaluation of the changes in the relationship of the PR interval and fetal heart rate during prolonged fetal compromise in sheep at levels of acidosis comparable to those seen during human fetal compromise and to see whether these changes are potentially of use in the detection of fetal distress. STUDY DESIGN: A retrospective analysis of continuous fetal electrocardiogram recordings during graded fetal hypoxemia in 20 chronically cannulated fetal sheep was performed. Baseline recordings during normoxemia were compared with recordings during hypoxemia by use of Fisher's exact test and the Student t test. RESULTS: Sixteen of the 20 cases could be used for final analysis. Twelve showed a statistically significant change from a predominantly negative relationship between the PR interval and the fetal heart rate during normoxemia to a predominantly positive relationship during hypoxemia. Two cases showed an obvious trend in the same direction, which was statistically not significant. In two other cases no change in the relationship was observed. CONCLUSION: A changing relation between the PR interval and the fetal heart rate is of potential use in the detection of fetal compromise.

Animals↗
PubMed2005

Fetal Doppler Hypoxic index for the prediction of abnormal fetal heart rate at delivery in chronic fetal distress.

OBJECTIVE: To design a Doppler Hypoxic index (HI), which takes into account both the duration and the intensity of fetal flow redistribution (i.e. hypoxia) for predicting the occurrence of abnormal fetal heart rate (FHR) at delivery. METHOD: Sixty-six pregnancies with hypertension and/or growth retardation (IUGR) were investigated (age: 23+/-5 years; primigravidas: 30%, CS 59%; hospitalisation: 10+/-8 days, IUGR (<10 c) 82%, intensive care 23%, fetal death 1). Umbilical (URI) and cerebral (CRI) Doppler resistance indices, and the C/U ratio (CRI/URI) were measured every 2 days from admission to delivery. HI was calculated by summing the daily %C/U reduction (in % from normal cut-off limit 1.1) over the period of observation (or mean C/U reduction in % from 1.1 x number of days of observation). Doppler C/U and HI were compared with fetal heart rate (FHR) traces, and perinatal data. RESULTS: HI > 160% was associated with abnormal FHR in 80% of the cases (PPV = 87%, NPV = 88%). HI > 160% predicted the occurrence of abnormal FHR 8+/-6 days before they happened. CONCLUSION: A combination of intensity and duration of the fetal flow redistribution (i.e. hypoxia) evaluated by Doppler is correlated with the occurrence of abnormal fetal heart rate.

Adult↗
PubMed1991

The effect of maternal cocaine use on the fetus: changes in antepartum fetal heart rate tracings.

Fetal heart rate tracings of pregnancies complicated by cocaine use were analyzed to evaluate the effects of subacute maternal cocaine use on the fetus. Nonstress tests were performed twice weekly on patients from the perinatal substance abuse clinic with screening of maternal urine samples for cocaine, amphetamines, phencyclidine, and opiates at the time of each examination. Nonstress tests performed when the urine toxicology screen was positive for cocaine alone (positive cocaine nonstress tests) were paired with those from the same patient but performed when the screen was negative (negative cocaine nonstress tests). The nonstress tests were analyzed with the Lyons scoring system, which evaluates the baseline heart rate, the oscillatory amplitude of the baseline, the oscillatory frequency, decelerations, and accelerations. Twenty pairs of nonstress tests from 20 patients were analyzed. The total score was higher on the negative cocaine nonstress test in 70% of the pairs and equal in the remaining 30% (p less than 0.001). Significant differences occurred in the oscillatory amplitude (p less than 0.001), frequency (p = 0.002), and acceleration scores (p = 0.03) but not the fetal heart rate baseline or the deceleration scores. The observed changes may reflect alterations in fetal central nervous system neurotransmitters and fetal state regulation, which may affect the developing central nervous system of cocaine-exposed fetuses and in turn play a role in the developmental and behavioral abnormalities observed in cocaine-exposed infants.

Cocaine↗
PubMed1989

The effects of vibratory acoustic stimulation on baseline fetal heart rate in term pregnancy.

Fetal heart rate responses to vibratory acoustic stimulation have been studied in normal and complicated pregnancies. To determine the precise nature of these responses, we studied 50 normal term fetuses with 60 minutes of electronic antepartum fetal heart rate monitoring divided in two 30-minute segments separated by 3 seconds of vibratory acoustic stimulation. All tracings were analyzed by a programmed microcomputer. Comparison of grouped mean 30-minute values before and after vibratory acoustic stimulation showed significant increases in baseline fetal heart rate, fetal heart rate variation, frequency of accelerations exceeding 10 and 15 beats/min, duration of accelerations exceeding 15 beats/min, and frequency of decelerations after vibratory acoustic stimulation. Mean baseline fetal heart rate elevation greater than 10 beats/min occurred within 7.6 +/- 4.4 seconds in 42 of 50 fetuses and lasted for 596 +/- 531 seconds. Reactive tests increased from 35 (70%) to 47 (94%) after vibratory acoustic stimulation. Most healthy term fetuses exhibit fetal heart rate responses after differing in frequency or magnitude from spontaneous fetal heart rate changes. Vibratory acoustic stimulation may be a valid fetal assessment tool but cannot be considered the physiologic equivalent of nonstress testing.

Acoustic Stimulation↗
PubMed1980

The significance of tachycardia during antenatal fetal heart rate monitoring.

Fetal tachycardia was observed in 130 of 4 509 patients (2,9%) in whom the fetal heart rate was monitored antenatally. These patients were compared with a control group of 379 patients who did not demonstrate fetal tachycardia. Indications for the tests were the same in the two groups. The prevalence of spontaneous uterine contractions, oxytocin administration, intra-uterine growth retardation, late deceleration during labour, and low Apgar scores and duration of pregnancy in the two groups did not differ significantly. Patients in the study group demonstrated significantly fewer accelerations but significantly more saltatory heart rate patterns. In the large majority of patients fetal tachycardia seemed to be an isolated observation, since most of the patients who were monitored before or after the tachycardiac episode demonstrated a normal fetal heart rate pattern. In some patients, however, fetal tachycardia could have indicated fetal compromise, since the contraction stress test became positive in significantly more patients in the study group (19%) than in the control group (2%).

Female↗
PubMed1996

Computerized fetal heart rate analysis and neural networks in antepartum fetal surveillance.

The use of computers for analysis of fetal heart rate has developed rapidly, enabling reproducible, objective analysis of fetal heart rate patterns. The problems of observer differences in visual assessment of fetal heart rate, and the continuum of antepartum and intrapartum fetal condition can be clarified through the use of such approaches. Computerized fetal heart rate analysis presents opportunities to perform precise evaluations of the effects of environmental conditions, medications, and disease states on fetal heart rate parameters.

Computer Communication Networks↗
PubMed1981

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.

Female↗
PubMed1980

Influence of occiput posterior position on the fetal heart rate pattern.

Fetal heart rate (FHR) recordings of 138 deliveries with the fetus in the occiput posterior position (OPP) are compared with recordings of 138 control fetuses in the occiput anterior position (OAP). The 2 groups are comparable in maternal age, parity, duration of first stage of labor, frequency of nerve blocks for analgesia, and incidence of cord complications. Variable decelerations were significantly more frequent and more pronounced in the OPP group than in the controls. The number of newborns with low Apgar scores was similar in both groups, despite a large number of pronounced decelerations in the OPP group. Possible mechanisms for the origin of variable decelerations in the occiput posterior position are discussed.

Female↗
PubMed1991

Fetal heart rate variability and cerebral oxygen consumption in fetal sheep during asphyxia.

This study was designed to examine the relationship between fetal heart rate variability and fetal cerebral oxygen uptake. Fetal sheep were chronically prepared with catheters and electrodes to determine cerebral blood flow (microsphere method), cerebral arteriovenous oxygen difference, and the electrocardiogram. An adjustable occluder was placed on the maternal common internal iliac artery to induce fetal asphyxia by reducing uterine blood flow. Fetal heart rate variability tended to decrease in the first 11 min of asphyxia, when cerebral oxygen consumption was approximately 53% of control. Despite stable cerebral oxygen consumption and worsening metabolic acidosis, however, fetal heart rate variability progressively returned towards normal by 36 min. There was no relationship between the depression of FHR variability and the degree of reduction of cerebral oxygen consumption. Nor was there any relationship between an alteration in regional cerebral blood flow or myocardial blood flow and the return of FHR variability with increasing duration of asphyxia. We conclude that there is an association between loss of fetal heart rate variability and reduced cerebral oxygen consumption, but the reduced variability does not persist with time at this degree of reduced cerebral metabolism in fetal sheep. This appears to be at variance with human clinical experience. Among the explanations for this may be insufficiently severe asphyxia, a species difference, removal of an inhibitor to FHR variability, or progressive use of other substrates for metabolism.

Animals↗
PubMed2000

Fetal heart rate monitoring: is it salvageable?

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

Asphyxia Neonatorum↗
PubMed1999

Intrapartum fetal heart rate monitoring.

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

Cardiotocography↗
PubMed1992

[Fetal echocardiography. II. Biometry of the normal fetal heart].

Normal fetal hearth biometry is analyzed by echocardiography in 80 pregnant women with 20 and 40 gestational weeks. Intraventricular septum, aorta, left and right ventricular dimensions were obtained. All dimensions showing progression with gestational age.

Biometry↗