Surveillance during labour

Computerized analysis of fetal heart rate variability signal during the stages of labor

AIM

To analyze computerized cardiotocographic (cCTG) parameters (baseline fetal heart rate, baseline FHR; short term variability, STV; approximate entropy, ApEn; low frequency, LF; movement frequency, MF; high frequency, HF) in physiological pregnancy in order to correlate them with the stages of labor. This could provide more information for understanding the mechanisms of nervous system control of FHR during labor progression.

METHODS

A total of 534 pregnant women were monitored on cCTG from the 37th week before the onset of spontaneous labor and during the first and the second stage of labor. Statistical analysis was performed using Kruskal-Wallis test and Wilcoxon rank-sum test with the Bonferroni adjusted α (< 0.05).

RESULTS

Statistically significant differences were seen between baseline FHR, MF and HF (P < 0.001), in which the first two were reduced and the third was increased when compared between pre-labor, and the first and second stages of labor. Differences between some of the stages were found for ApEn, LF and for LF/(HF + MF), where the first and the third were reduced and the second was increased.

CONCLUSIONS

cCTG modifications during labor may reflect the physiologic increased activation of the autonomous nervous system. Using computerized fetal heart rate analysis during labor it may be possible to obtain more information from the fetal cardiac signal, in comparison with the traditional tracing.

Litigation related to intrapartum fetal surveillance

The role of intrapartum care including cardiotocography (CTG) monitoring in cases of perinatal neurological injury receives considerable debate in both clinical and medicolegal settings. The debate, however, has distracted attention from fundamental questions about the timing, mechanism, and preventability of perinatal injury. CTG tracings are used as a surrogate for asphyxia with the timing of intervention ("rescue") predicated on the presumed severity of asphyxia. Using CTG in this way has prevented intrapartum stillbirth, but it has not reduced the long-term injury in part, because, contrary to popular belief, the majority of intrapartum fetal injuries are unassociated with severe hypoxia or severe neonatal depression. This article describes the timing and mechanisms, including mechanical factors, of intrapartum perinatal injury and the benefit of using the CTG, not for the purpose of "rescue", but for identifying risk factors for fetal injury and keeping the fetus out of harm's way.

Impact of fetal pulse oximetry and ST analysis surveillance withdrawal on rates of obstetric surgery and frequency of low birth umbilical artery pH: a cause of rising caesarean rates?

A retrospective observational study on a sample of 13,413 deliveries analysed the effect of a withdrawal of the CTG additional diagnostic methods of fetal hypoxia (fetal pulse oximetry and ST analysis of the fetal ECG) on operative delivery rates and frequency of the umbilical arterial pH < 7.15. Following the withdrawal, obstetricians are more likely to perform caesarean sections for fetal hypoxia (OR 2.23, 95% CI 1.94-2.55, p < 0.0001) and labour dystocia (OR 1.45, 95% CI 1.18-1.77, p = 0.0003), which increases the overall caesarean rate (OR 1.49, 95% CI 1.38-1.61, p < 0.0001), although decreases the incidence of birth umbilical arterial pH < 7.15 (OR 0.43, 95% CI 0.22-0.85, p = 0.015). This also leads to the significant decline in overall frequency of instrumental vaginal deliveries (OR 0.58, 95% CI 0.48-0.71). In order to decrease the overall caesarean rate, obstetricians need to be supported by more accurate and possibly automated diagnostic tools for intrapartum fetal hypoxia.

How often is a low Apgar score the result of substandard care during labour?

Please cite this paper as: Berglund S, Pettersson H, Cnattingius S, Grunewald C. How often is a low Apgar score the result of substandard care during labour? BJOG 2010;117:968-978. Objective To increase our knowledge of the occurrence of substandard care during labour. Design A population-based case-control study. Setting Stockholm County. Population Infants born in the period 2004-2006 in Stockholm County. Methods Cases and controls were identified from the Swedish Medical Birth Register, had a gestational age of >/=33 complete weeks, had planned for a vaginal delivery, and had a normal cardiotocographic (CTG) recording on admission. We compared 313 infants with an Apgar score of <7 at 5 minutes of age with 313 randomly selected controls with a full Apgar score, matched for year of birth. Main outcome measure Substandard care during labour. Results We found that 62% of cases and 36% of controls were subject to some form of substandard care during labour. In half of the cases and in 12% of the controls, CTG was abnormal for >/=45 minutes before birth. Fetal blood sampling was not performed in 79% of both cases and controls, when indicated. Oxytocin was provided without signs of uterine inertia in 20% of both cases and controls. Uterine contractions were hyperstimulated by oxytocin in 29% of cases and in 9% of controls, and the dose of oxytocin was increased despite abnormal CTG in 19% and 6% of cases and controls, respectively. Assuming that substandard care is a risk factor for low Apgar score, we estimate that up to 42% of the cases could be prevented by avoiding substandard care. Conclusions There was substandard care during labour of two-thirds of infants with a low Apgar score. The main reasons for substandard care were related to misinterpretation of CTG, not acting on an abnormal CTG in a timely fashion and incautious use of oxytocin.