Sze-Ya Yeh

Clinical fetal monitoring. VII. The evaluation and significance of intrapartum baseline FHR variability.

The clinical usage of intrapartum fetal monitoring has increased dramatically in the past few years. Understanding of the pathophysiologic significance of FHR patterns has been further elucidated, but quantitation and prediction on an individual basis at times present a practical clinical dilemma. Baseline FHR variability was evaluated in order to see if it provided additional commentary on fetal status. The presence of FHR variability appears to be a favorable commentary regarding both fetal and newborn status. A clinical method of apprasing FHR is presented and the significance of FHR variability suggested.

Trial of labor in the patient with a prior cesarean birth

The increasing incidence of cesarean birth has become quite controversial. The practice of delivering virtually all women with a prior cesarean section by repeat cesarean section is open to debate. In a large institutional practice, with rapid availability of all support services, selective attempts to deliver women vaginally, after a prior cesarean section, is appealing. A prospective 1-year study on all patients with a prior cesarean delivery commenced July 1, 1982. There were 1209 patients, of whom 751 (62%) underwent a trial of labor and 614 (82%) achieved vaginal delivery. There was no maternal mortality or perinatal mortality attributed to the trial of labor process. Oxytocin usage occurred in 38% of this population. The incidence of uterine rupture and scar dehiscence was similar in the various study subgroups. The overall group of women undergoing a trial of labor had significantly fewer postpartum complications and shorter hospital stays.

Significance of meconium during labor.

Continuous fetal heart rate (FHR) monitoring and routine fetal scalp blood sampling was utilized in the evaluations of 366 fetuses during labor. One hundred and six patients had meconium in the amniotic fluid at some time during labor. A total of 26,110 uterine contractions were monitored during these 366 labors. The incidence of FHR patterns as a percentage of uterine contractions was calculated for the meconium and nonmeconium groups. Although there was a 3 1/2-fold increase in the incidence of low five-minute Apgar scores (less than 7) in the meconium group, signs of fetal distress were, with rare esception, not significantly different from those in the nonmeconium group. The presence of meconium in the amniotic fluid without signs of fetal asphyxia (late decelerations and acidosis) is not a sign of fetal distress and need not be an indication for active intervention. The combination of fetal asphyxia and meconium staining of the amniotic fluid, however, does enhance the potential for meconium aspiration and a poor neonatal outcome. Universal fetal heart rate monitoring and appropriate fetal acid-base evaluation is recommended for following patients with meconium in the amniotic fluid during labor.

The role of ultrasound assessment of amniotic fluid volume in the management of the postdate pregnancy

Antepartum assessments of amniotic fluid volumes and their relationship to nonstress test patterns and pregnancy outcomes were retrospectively analyzed in 234 postdate pregnancies. The incidence of clinical oligohydramnios and a nonstress test revealing fetal heart rate deceleration or bradycardia was found to increase as the sonographic estimates of the amniotic fluid volume decreased. Furthermore, the postdate pregnancy with sonographic evidence of an adequate amniotic fluid volume had a significantly better perinatal outcome than the pregnancy without an adequate fluid volume. These results suggest that the postdate pregnancy with evidence of reduced amniotic fluid volume should be considered for a trial of labor with continuous electronic fetal monitoring.

Respiratory sinus arrhythmia in the human fetus

This study explores the relationship between fetal heart rate variability and fetal breathing movements in the term fetus. Fourier analysis was applied to fetal heart rate variability during fetal breathing and nonbreathing episodes. A distinct component in the order of 0.7 to 0.95 Hz was demonstrated in fetal heart rate variability during breathing episodes. These frequencies have the same distribution as the corresponding rate of breathing and therefore indicate that respiratory sinus arrhythmia exists in the term fetus.

Autocorrelation techniques in fetal monitoring

Fetal monitors that feature autocorrelation have recently been introduced. This paper discusses autocorrelation and describes how it extracts periodic signals from a noisy background. An example of its performance under clinical conditions demonstrating advantages and limitations is discussed.

Ten-year experience of intrapartum fetal monitoring in Los Angeles County/University of Southern California Medical Center

During the 10-year period from 1970 to 1979, a total of 115,096 deliveries occurred at the Los Angeles County/University of Southern California Medical Center. Of these, 47,567 patients (41.3%) were monitored during labor and delivery. The intrapartum monitoring technique was initially introduced in late 1969. The monitoring rate increased gradually from 18% in 1970 to 74% in 1979. The perinatal mortality rate during this 10-year period was 24.4/1,000. The perinatal mortality rate decreased in an inverse proportion to the monitoring rate. The main portions of the decrease in perinatal mortality rate were in the intrapartum and neonatal death rates. Both the fetal death rate and the neonatal death rate were significantly lower in the monitored patients than in those who were not monitored. This was irrespective of the fact that most high-risk patients were included in the monitored group. The cesarean section rate during this period increased slightly from 9.3% in 1970 to 12.3% in 1979. The primary cesarean section rate increased from 6.4% in 1970 to 8.7% in 1979. These findings suggest the beneficial role of intrapartum fetal monitoring and its association with diminished perinatal losses.

Fetal and neonatal biochemistry and Apgar scores

Abstract Biochemical changes during labor, delivery, and the first hour of life were evaluated in 150 high-risk pregnancies. No differences in the biochemical status of the fetus (pH, Po 2 , Pco 2 , and base deficit) were found during early labor with different groups of patients divided according to low or high Apgar scores at 1 and 5 minutes. During labor and delivery, the fetus gradually becomes acidotic, with the acidosis more marked in fetuses who subsequently had lower Apgar scores; at birth there was a momentary accentuation of the acidosis during the first few minutes of life. It is speculated that the prediction of Apgar scores may be possible by measuring the fetal pH during the course of labor and delivery and that serial biochemical measurements with guide preparation for adequate treatment of a depressed newborn infant.

Observations of fetal heart rate characteristics related to external cephalic version and tocolysis

External cephalic version performed in conjunction with tocolysis in the term breech presentation has been found to decrease the number of breech presentations at delivery and thus reduce the number of cesarean sections for breech presentation. However, information regarding the fetal heart rate (FHR) patterns associated with version is limited. In an attempt to broaden our understanding of the FHR changes that occur in association with version, the FHR tracings of 141 patients who had undergone version were analyzed. Approximately 39% of the fetuses exhibited changes in FHR characteristics during and/or after attempted version. These FHR changes were primarily manifested as bradycardias and/or decelerations. However, some of the fetuses (less than 5%) demonstrated a tachycardia or sine wave pattern. All of these FHR changes were transient and bore no apparent relationship to the subsequent outcome of the fetus. In addition to these FHR alterations, the incidence of diminished FHR variability (less than or equal to 5 bpm) was significantly higher after version than before version (p less than 0.01). The decline in FHR variability lasted 15 +/- 12 minutes. While this decline in variability appeared to be related to the success or failure of the version, the decreased variability observed after version was found to be unrelated to the tocolytic agent used and to the subsequent fetal outcome. In summary, alterations in FHR activity were frequent during the version process. All were transient and most responded to cessation of manipulation. Subsequent fetal outcome was apparently unrelated to the observed FHR alterations. Nonetheless, continuous fetal monitoring during and after the version is recommended.

The effects of ritodrine hydrochloride on uterine activity and the cardiovascular system.

The effects of ritodrine hydrochloride were evaluated in 10 patients in active labor with continuous electronic monitoring of fetal and maternal cardiovascular systems and uterine activity. Ritodrine infused at 150 μg per minute significantly decreased uterine activity and increased maternal heart rate with only minimal blood pressure changes. During the period of increased maternal heart rate, nonspecific changes in the maternal electrocardiogram were noted and thought to be rate related. The drug has no demonstrable effect on the fetal heart rate, fetal electrocardiogram, or acid-base status.