Electronic fetal heart rate monitoring during labour: does it prevent perinatal asphyxia and cerebral palsy?

Correlation of arterial fetal base deficit and lactate changes with severity of variable heart rate decelerations in the near-term ovine fetus

OBJECTIVE

Recent guidelines classify variable decelerations without detail as to degree of depth. We hypothesized that variable deceleration severity is highly correlated with fetal base deficit accumulation.

STUDY DESIGN

Seven near-term fetal sheep underwent a series of graded umbilical cord occlusions resulting in mild (30 bpm decrease), moderate (60 bpm decrease), or severe (decrease of 90 bpm to baseline <70 bpm) variable decelerations at 2.5 minute intervals.

RESULTS

Mild, moderate, and severe variable decelerations increased fetal base deficit (0.21 ± 0.03, 0.27 ± 0.03, and 0.54 ± 0.09 mEq/L per minute) in direct proportion to severity. During recovery, fetal base deficit cleared at 0.12 mEq/L per minute.

CONCLUSION

In this model, ovine fetuses can tolerate repetitive mild and moderate variable decelerations with minimal change in base deficit and lactate. In contrast, repetitive severe variable decelerations may result in significant base deficit increases, dependent on frequency. Modified guideline differentiation of mild/moderate vs severe variable decelerations may aid in the interpretation of fetal heart rate tracings and optimization of clinical management paradigms.

Intrapartum assessment of fetal well-being: any role for a fetal admission test?

OBJECTIVE

To determine whether the fetal admission test is predictive of intrapartum complications.

METHODS

We studied the fetal heart rate tracings of women in spontaneous labor at 37-42 weeks' gestation from 1 November 2001 to 31 March 2002. The study population was subdivided based on reactivity defined as > or = 15 beats/min for > or = 15 s, reactivity redefined as > or = 10 beats/min for > or = 10 s, variability, presence of late and/or variable decelerations, and reassuring fetal admission test; and compared for various labor outcome variables. Student's t test, the chi2 test and Fisher's exact test were used for analysis.

RESULTS

A total of 426 women met our inclusion criteria. There were no differences between groups when compared for maternal age, parity, gestational age, birth weight, labor analgesia and length of labor. Irrespective of the definition of reactivity, women with a non-reactive fetal admission test were more likely to be delivered by Cesarean section, to have fetal distress resulting in Cesarean section and to have a longer neonatal hospital stay. In addition, redefining reactivity improved the specificity, positive and negative predictive values, accuracy, relative risk and likelihood ratio with regard to development of fetal distress. Similar results were obtained when variability and decelerations were used as criteria for comparisons.

CONCLUSION

The fetal admission test is useful in predicting the absence of intrapartum fetal distress irrespective of the criterion used for evaluation. Redefined reactivity appears to be most predictive of intrapartum fetal distress.

Human fetal intrapartum oxygen saturation monitoring: agreement between readings from two sensors on the same fetus

OBJECTIVE

Our purpose was to assess the level of agreement between oxygen saturation values obtained from two identical sensors used on different sides of the face of the same human fetus during labor.

STUDY DESIGN

Two identical fetal pulse oximeter sensors were placed on 12 fetuses during uncomplicated labor at < or = 38 weeks' gestation. Oxygen saturation, fetal heart rate, and uterine activity were recorded. The agreement between synchronous values of oxygen saturation was assessed by calculating the mean difference and SD of the difference. The SD of a single sensor was estimated as the SD of the difference divided by the square root of 2.

RESULTS

The mean oxygen saturation value returned from one sensor was 49.2% and from the other 49.9%; the mean difference was -0.7%. The SD of the difference was 7.5%, and the 95% limits (+/- 2 SDs of the difference) were -15.5% to 14.1%. The SD from a single sensor was estimated as 5.3%.

CONCLUSIONS

There was no clinically significant difference between the oxygen saturation values returned from two identical sensors on the one fetus. The magnitude of the SD from a single sensor must be taken into account when an arbitrary "cutoff" or "action" oxygen saturation value in a clinical setting or trial is defined.

Model to identify potentially preventable cerebral palsy of intrapartum origin

A six stage model was applied to a geographically defined population of 210 singleton children born at term who had a diagnosis of cerebral palsy at 5 years of age. Thirty five children were identified as those most likely to have cerebral palsy of intrapartum origin; in 26 of these there was evidence of suboptimal care. It is suggested that this simple model should be tested on populations of children with cerebral palsy and the underlying principles used when considering the likely cause of cerebral palsy in individual children.

Fetal monitoring during air medical transport

A prior survey of physiologic monitoring practices during maternal air medical transport by helicopter found that cardiotocography is rarely utilized. The authors report their experience with fetal heart-rate monitoring during helicopter transport of high-risk mothers. The technique is as readily applied to the care of the patient in a helicopter as it is in the modern labor and delivery suite. The study found no substantial reasons why such monitoring should not be used in air medical transport.

Prospective study of the quality of survival of infants with critical fetal reserve detected by antenatal cardiotocography

From 1981 to 1986 antenatal cardiotocographic monitoring was performed on 9,992 high-risk pregnancies selected from a total obstetrical population of 31,518 patients (31.7%). A critical fetal reserve pattern was detected in 89 patients (0.9%) whose pregnancies resulted in 68 surviving infants, 19 perinatal deaths and 2 sudden infant deaths. Since 47.4% of the infants who died in the perinatal period did so because of a related congenital malformation, such a defect should be excluded in the fetus with critical fetal reserve, by ultrasonography, before delivery (there is usually insufficient time for fetal karyotyping). Sixty-three (92.6%) of the surviving children were assessed at our Growth and Developmental Clinic and disabilities were detected in 16 (25.4%); however, the disability was major in only 5, including 2 children with Down syndrome. The quality of survival of infants born from pregnancies complicated by critical fetal reserve was satisfactory as 60 of 63 children (95.2%) had neither a major disability related to intrauterine hypoxia identified by the cardiotocographic pattern, or had one likely to significantly interfere with their quality of life. Our results suggest that pregnancies can be continued until the cardiotocographic pattern becomes critical in order to gain fetal maturity, without compromise to the fetal brain.

Why have we failed to reduce the frequency of cerebral palsy?

OBJECTIVE

To review the data on children with cerebral palsy in relation to quality of obstetric care.

DATA SOURCES AND STUDY SELECTION

In our Institute, a regular Medline print-out, certain key journals and Current Contents are perused to create an updated computerised file of publications on the epidemiological, aetiological and other aspects of cerebral palsy. For this study we reviewed data from the Western Australian Cerebral Palsy Register, more than 150 publications from which studies were chosen for sound methodology in countries with modern obstetric practices, and recent population data on cerebral palsy.

DATA EXTRACTION AND SYNTHESIS

Three major areas were studied to see: (i) if the prevalence of cerebral palsy has fallen with increasing use of obstetric and neonatal interventions aimed at reducing birth asphyxia; (ii) if there is any evidence that cerebral palsy is caused by birth asphyxia; and (iii) if there is any evidence that intrapartum fetal monitoring or caesarean section reduces the prevalence of cerebral palsy.

CONCLUSIONS

We concluded that: cerebral palsy proportions are not falling in spite of significant increases in obstetric and neonatal interventions aimed at reducing asphyxia; cerebral palsy proportions in low birthweight infants are rising in most developed countries, coincident with increases in the neonatal survival of low birthweight babies; few cases of cerebral palsy seem to be caused by birth asphyxia and those that are may not have been preventable by obstetric care; and parents will continue to sue if obstetricians keep promising perfection from obstetric care in the face of 2.0-2.5 cases of cerebral palsy per 1000 children born.