Fetal Heart Rate Recordings Research Articles

Correlation of the interpretation of fetal heart rate records with cord plasma erythropoietin levels.

On the basis that fetal levels of plasma erythropoietin (Ep) may reflect fetal oxygenation the primary purpose of the present study was to assess the relation between Ep measured in cord plasma at delivery and the intrapartum fetal heart rate (FHR) record. A scoring system for interpreting FHR recordings blindly was prospectively utilized in 41 selected human pregnancies during the 4 h immediately preceding birth. The correlation of the overall mean FHR score for each individual patient with cord plasma Ep was significant such that the highest Ep levels were observed in those infants with the most abnormal FHR scores. Furthermore, when the birthweights of the infants were adjusted for gestational age, sex, and birth order, birthweight centile was negatively correlated with cord plasma Ep. When both FHR score and birthweight were simultaneously correlated with cord plasma Ep using multiple regression, the combined effect of these two factors improved the association of either alone with both contributing approximately equally.

Baseline fetal heart rates from 15 to 38 weeks gestation in normotensive and hypertensive pregnancies.

To determine whether the fetal heart behaves differently in normotensive and hypertensive pregnancies, the changes in baseline fetal heart rate were investigated prospectively from 15 to 38 weeks gestation in 16 women who were normotensive at the time of booking in the antenatal clinic. Fetal heart rate recordings were made ultrasonically, and were computer-processed by the programs TELEPLOT and BASELINE. Those women who remained normotensive exhibited a decrease of fetal heart rate with advancing gestational age, but this did not occur in the six women who eventually developed hypertension.

Changes in the fetal heart rate of thoroughbred horse through the gestation.

Fifty-nine recordings of fetal and maternal heart rate (FHR and MHR) were made from 10 pregnant Thoroughbred mares. Each recording lasted for an average of 20 min. The heart rate was calculated at an interval of 10 sec from beat to beat using the R or S wave of the fetal electrocardiograms as the indicator of each heart-beat. FHR was classified into the baseline FHR and the FHR acceleration, the latter of which was a brief tachycardia occasionally observed. The baseline FHR decreased logarithmically with the advance in gestational period, while the mean MHR increased. The frequency and the magnitude of the FHR acceleration increased at the later period of gestation, suggesting the development of fetal body movements.

Heart-rate variation and movement incidence in growth-retarded fetuses with decelerative heart rate patterns. Correlations with fetal acid-base status

Publisher Summary This chapter discusses when heart rate variation and movements decrease in intrauterine growth-retarded fetuses (IUGR) fetuses. It also discusses their relationship to the acid–base status at delivery. The chapter presents the first results obtained from 18 IUGR fetuses from whom combined recordings of fetal heart rate (FHR) and fetal motility were obtained shortly before Caesarean section. Although the IUGR group consisted of highly compromised fetuses, according to the antenatal FHR tracings, only one of the liveborn infants had a pHua lower than 7.15. This finding confirms earlier studies showing that only terminal heart rate records are associated with fetal acidemia. Hypoxia, on the other hand, may play a role as umbilical arterial PO 2 values were significantly lower than in the control group. From experimental studies in growth retarded fetal sheep, it is known that low arterial PO 2 values precede acidemia. A further indication for the role of hypoxia is the fact that the reduction of heart rate variation apparently coincides with the occurrence of late decelerations, the latter being thought to indicate hypoxemia. As for the body movement incidence, there is a weak relationship with the umbilical artery pH and this might become more evident if more fetuses in a terminal condition can be included in the study group. Further research is required to ascertain the particular effects of low PO 2 values or preferably of accurately measured oxygen saturation.

Progresses in Fetal Monitoring by Improved Data Acquisition

INCE the possibilities of gaining information on the fetal condition by non-invasive means are limited to only a few procedures, such as re­ cording of fetal heart action and ultra­ sonic imaging, expanding the diag­ nostic potential is a great biomedical engineering challenge. Instead of searching for new, complicated mea­ suring techniques that are often de­ clined by the medical staff, this chal­ lenge can be met by developing suitable procedures aimed at improv­ ing the analysis of data provided by present routine examinations. Car­ diotocography (CTG) is the most com­ monly used method in perinatal moni­ toring, but serious difficulties still attach to its interpretation. In many cases, an unequivocal diagnosis is not possible without first obtaining addi­ tional physiological information. The reasons may be either physiological or due to shortcomings of existing in­ strumentation. Both problems could be solved by improving the processing of available bioelectric signals, and by developing a new physiological model of the maternal influence on the fetal cardiovascular system, permitting a more reliable interpretation of the CTG. Fetal Heart Rate Recording Heart action is the only vital func­ tion of the fetus that can be recorded effectively without lesion. Conse­ quently, fetal heart rate (FHR) analy­ sis, related to uterine pressure, is the most important method in prenatal monitoring. Using non-invasive meth­ ods, heart action can be assessed by: -the electrocardiogram (ECG), picked up from the material abdo­ men,

Baseline: A computer method of calculating baseline in fetal heart rate recordings

‘Baseline’ estimation is of fundamental importance in both visual and numerical analysis of fetal heart rate recordings, even though the baseline itself is in reality an imaginary line. Here we describe a linear method of estimating baseline in fetal heart rate recordings. The method is easy to implement on a digital computer, and is capable of precise mathematical analysis. Non-linear methods, on the other hand, introduce unpredictable and non-quantifiable statistical bias, and are best avoided.

Teleplot: A computing system for objective analysis of fetal heart rate recordings

In human pregnancies, fetal heart rate recordings are useful both in predicting and in preventing imminent fetal death. Although an objective numerical measurement of such recordings is preferable to visual analysis, few obstetric centres have the computer expertise to implement this. Here we describe the principles of a technique whereby the fetal heart rate versus time trace may be transferred into computer memory for further processing in a numerical and objective fashion. The methodology is valid howsoever the fetal heart rate is detected.

Fetal Heart Rate Patterns and Perinatal Outcome of Very-Low-Birthweight Infants

Summary. The obstetric records of 125 infants weighing 500–1250 g who were born in 1978 and 1979 at the Helsinki University Central Hospital were studied retrospectively to find out any associations between fetal heart rate (FHR) patterns and perinatal outcome. FHR recordings of 79 fetuses were available for study. Normal reactive patterns were observed in nine, nonreactive in 54, decelerations in 58, silent patterns in 45 and combined distress patterns in 36 fetuses. The interval from the first pathological sign to delivery was up to 27 days. Five fetuses in the monitored group died in utero, 26 infants died neonatally and two later. The risk of neonatal death after pathological FHR patterns was lower than after an FHR pattern without abnormality. Idiopathic respiratory distress syndrome (RDS) was diagnosed in 32 infants, of whom 16 died. Forty-seven fetuses (59%) of the monitored group were delivered abdominally and 32 vaginally. The risk of RDS was not significantly associated with FHR patterns and mode of delivery. We conclude that unlike term fetuses, low-birthweight fetuses seem to benefit from a period of intrauterine stress reflected in abnormal FHR patterns, if caesarean section is used liberally.

Fetal heart rate patterns and perinatal outcome of very-low-birthweight infants.

The obstetric records of 125 infants weighing 500-1250 g who were born in 1978 and 1979 at the Helsinki University Central Hospital were studied retrospectively to find out any associations between fetal heart rate (FHR) patterns and perinatal outcome. FHR recordings of 79 fetuses were available for study. Normal reactive patterns were observed in nine, nonreactive in 54, decelerations in 58, silent patterns in 45 and combined distress patterns in 36 fetuses. The interval from the first pathological sign to delivery was up to 27 days. Five fetuses in the monitored group died in utero, 26 infants died neonatally and two later. The risk of neonatal death after pathological FHR patterns was lower than after an FHR pattern without abnormality. Idiopathic respiratory distress syndrome (RDS) was diagnosed in 32 infants, of whom 16 died. Forty-seven fetuses (59%) of the monitored group were delivered abdominally and 32 vaginally. The risk of RDS was not significantly associated with FHR patterns and mode of delivery. We conclude that unlike term fetuses, low-birthweight fetuses seem to benefit from a period of intrauterine stress reflected in abnormal FHR patterns, if caesarean section is used liberally.

Antenatal fetal heart-rate variability in relation to fetal acid-base status at caesarean section.

A quantitative comparison was made of fetal heart-rate (FHR) traces obtained shortly before delivery, and of umbilical artery blood gas values, in 49 women delivered by caesarean section for reasons other than fetal compromise and in 23 women delivered by section for antenatal fetal compromise judged from visual inspection of conventional FHR recordings. The FHR traces in the compromised group of fetuses were abnormal, with low variability and a high incidence of decelerations, but there was no significant difference from the normal group in metabolic acidaemia, as judged by the base excess of umbilical artery blood. The compromised group consisted almost exclusively of infants small-for-gestational age. These results suggest that the FHR pattern of the compromised fetuses is not the direct result of intrauterine asphyxia but of some other factor associated with growth retardation.

A One-Year Study of Routine Fetal Heart Rate Monitoring during the First Stage of Labor

At the Department of Obstetrics and Gynecology, University Hospital, Lund, Sweden 90 per cent of all deliveries are monitored with cardiotocography (CTG). The fetal heart rate recording (FHR) together with various pregnancy- and delivery data, are continuously analysed. The present paper is an account of FHR changes during the first stage of labor of all patients registered during 1977. FHR-changes occurred already during the 1st stage of labor in more than 90 per cent of all deliveries where the newborns' Apgar score was less than 7 at 1 minute. Tachycardia, silent pattern, and late and combined decelerations, rarely occurred in the material, but were dominant at deliveries where the newborns' Apgar score was less than 7 at 1 and 5 minutes. This relationship was even more pronounced when these changes occurred together.

Abnormal Fetal Heart Rate Associated with Congenital Abnormalities

Summary The fetal heart rate (FHR) records obtained from 3140 patients were reviewed. Thirty-seven patients gave birth to an infant with a major congenital abnormality. Fifty-one per cent of this group demonstrated an abnormal FHR in the antepartum or intrapartum period. The Caesarean Section rate was 48 per cent and perinatal mortality was 50 per cent. In patients with an abnormal antepartum FHR record, an underlying congenital abnormality of the fetus should be considered.

The influence of observer-dependent properties upon the evaluation of fetal heart rate recordings (author's transl)

The significance of the observer's experience in the evaluation of fetal heart rate (FHR) recordings has not yet been dealt with in the literature. Therefore the qualitative and quantitative determination of these subjective factors has been studied as follows at the University of Basle Department of Obstetrics and Gynecology: Twenty FHR recordings were simultaneously analyzed by twenty-five residents with different levels of obstetrical experience. The results were compared with those of physicians with expertise in FHR monitoring. It became obvious that ominous antepartum FHR tracings were significantly less often correctly identified than harmful intrapartum recordings (p less than 0.001). Harmless changes in intrapartum FHR tracings were more frequently misjudged as being ominous than normal antepartum FHR tracings (p less than 0.05). The following conclusions were made: - There is a real danger of a fatal error in the interpretation of ominous antepartum FHR recordings. - The presented data seem to reveal the source of the increased caesarean section rate described by others as to be associated with FHR monitoring. - The errors in the interpretation of FHR tracings decrease significantly (p less than 0.05) with increasing experience. Thus physicians' education is eminently important for the correct use of electronic fetal monitoring.

Evaluation of the Corometrics 315 telemetry system for fetal monitoring

The Corometrics 315 telemetry system is a commercially available unit which can transmit both fetal heart rate (FHR) and intrauterine or external pressure data to a standard fetal monitor. This system was evaluated in 40 patients, ten of whom were monitored simultaneously by telemetry and direct-wire fetal monitoring. Because of some differences in electronic engineering between the telemetry and direct fetal monitoring systems, the following differences were found: Comparison of the simultaneously obtained FHR recordings revealed that the telemetry system rejected most of the motion artifacts while maintaining true variability. There were no differences as regards readability, FHR, and beat-to-beat variability. The intrauterine pressure values were the same, although the telemetry system gave a smoother waveform with less motion artifact. The main advantages of the telemetry system were found to be: (1) The patient was free to move about and ambulate during labor. (2) It was possible to obtain uninterrupted monitoring while the patient was moved from the labor room to the delivery room and throughout the second stage of labor.

Changes in the fetal heart rate associated with fetal breathing and fetal movement.

Thirty-eight recordings of fetal heart rate and fetal activity were made from 21 normal patients between 36 and 41 weeks gestation. Each recording lasted for an average of 39 minutes. The heart rate was measured from beat to beat using the R-wave of the fetal electrocardiogram as the indicator of each heart-beat. Fetal breathing movements and fetal body movements were detected using either A-mode or B-mode ultrasound systems. The relation of fetal breathing and fetal movement to the fetal heart rate was studied both by cardiotachography and computer analysis of the R--R intervals. Fetal body movements (kicking and rolling) were usually associated with a brief tachycardia, the latter typically occurring every two to three minutes. In 14 recordings, the periods of fetal activity were interrupted by periods of fetal rest with an average duration of 12.5 minutes. Fetal breathing was seen in 26 of the 34 recordings analysed and occurred principally during the periods of fetal activity. Fetal breathing was associated with a significant increase in heart rate variation measured as the standard deviation of the R--R intervals and the mean absolute R--R interval difference. Sometimes a pattern of respiratory sinus arrhythmia was seen.

Fetal heart rate monitoring using the abdominal fetal electrocardiogram.

An evaluation of a prototype abdominal fetal electrocardiogram (ECG) module for use in a Sonicaid FM3R monitor is described; 103 antenatal recordings of fetal heart rate (FHR) were attempted in 56 patients between 21 and 43 weeks gestation. The overall success rate was 54 per cent but the proportion of successful recordings was reduced between 24 and 36 weeks gestation. Most successful recordings were obtained with the first electrode placings and the quality of the recordings was generally higher than those obtained by simultaneously recorded FHR from ultrasound. Monitoring using the abdominal ECG during parturition was found to be unreliable. The advantages of the method are that it is non-invasive, the patient is not restricted by belts and the technique is easy to apply. However the uncertainty of obtaining a FHR trace between 24 and 36 weeks gestation is a major disadvantage.

ABNORMAL FETAL HEART RATE ASSOCIATED WITH CONGENITAL ABNORMALITIES

The fetal heart rate (FHR) records obtained from 3140 patients were reviewed. Thirty-seven patients gave birth to an infant with a major congenital abnormality. Fifty-one per cent of this group demonstrated an abnormal FHR in the antepartum or intrapartum period. The Caesarean Section rate was 48 per cent and perinatal mortality was 50 per cent. In patients with an abnormal antepartum FHR record, an underlying congenital abnormality of the fetus should be considered.

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.

A one-year study of routine fetal heart rate monitoring during the first stage of labor.

At the Department of Obstetrics and Gynecology, University Hospital, Lund, Sweden 90 per cent of all deliveries are monitored with cardiotocography (CTG). The fetal heart rate recording (FHR) together with various pregnancy- and delivery data, are continuously analysed. The present paper is an account of FHR changes during the first stage of labor of all patients registered during 1977. FHR-changes occurred already during the 1st stage of labor in more than 90 per cent of all deliveries where the newborns' Apgar score was less than 7 at 1 minute. Tachycardia, silent pattern, and late and combined decelerations, rarely occurred in the material, but were dominant at deliveries where the newborns' Apgar score was less than 7 at 1 and 5 minutes. This relationship was even more pronounced when these changes occurred together.

Intrauterine fetal arrhythmia: atrial premature beats.

A case of antepartum fetal arrhythmia is reported. The diagnosis of atrial premature beats was confirmed during labor by simultaneous recording of fetal heart rate and fetal electrocardiogram. The possibility of fetal distress during labor was excluded by fetal heart rate and acid-base monitoring. The difficulty of reaching a definitive antepartum diagnosis of the arrhythmia and its significance in relation to fetal well-being are discussed.