Physiological CTG interpretation: the significance of baseline fetal heart rate changes after the onset of decelerations and associated perinatal outcomes.

OBJECTIVE: To determine the perinatal outcomes in fetuses with baseline fetal heart rate changes with preceding decelerations on the cardiotocography (CTG) trace, and to interpret CTG traces from the aspect of fetal physiology. MATERIALS AND METHODS: A retrospective analysis of 500 consecutive CTG traces was carried out. The presence of repetitive variable and late decelerations followed by the changes in the baseline including baseline tachycardia and abnormal baseline variability were determined. Perinatal outcomes including Apgar scores and umbilical arterial pH at birth, NNU admission, and meconium-stained amniotic fluid were analyzed. We interpreted the changes in CTG based on fetal physiology. RESULTS: When repetitive variable and late decelerations were present without tachycardia (n = 81), none of the fetuses had an Apgar score <7 at 5 minutes or an umbilical cord pH <7. After the onset of fetal tachycardia (n = 262), fetuses showed decreased Apgar scores and umbilical arterial pH(p < .01), however, there was no significant difference in the rate of abnormal 5 min Apgar score, abnormal PH and NNU admission, if the baseline variability remained normal. However, if the baseline variability was abnormal (n = 44), (either increased or reduced) after tachycardia, there was a statistically significant increase in poor perinatal outcomes. Fetuses with abnormal versus normal variability had lower Apgar scores ≤7 at 5 min (29.6 versus 0.9%, p = .000); umbilical cord arterial pH <7 at birth (29.5 versus 0%, p = .000); increased admission to the NNU (27.3 versus 3.7%, p = .000) and increased incidence of meconium-stained amniotic fluid (38.6 versus 22.5%, p = .024). These serial changes in CTG could be interpreted and predicted by the application of fetal physiology. CONCLUSIONS: There were significant differences in perinatal outcomes when fetuses were exposed to evolving intrapartum hypoxic stress culminating in an abnormal baseline fetal heart rate variability, which was preceded by repetitive decelerations, followed by an increase in the baseline heart rate. However, despite ongoing decelerations, if the baseline variability remained normal, none of the fetuses had a pH of <7. Therefore, the knowledge of fetal physiological response to evolving hypoxic stress can be reliably used to determine fetal compensation.

Types of intrapartum hypoxia on the cardiotocograph (CTG): do they have any relationship with the type of brain injury in the MRI scan in term babies?

Electronic foetal monitoring using cardiotocography is aimed at the timely recognition and management of foetal hypoxia. The primary objective of this study was to examine whether a relationship exists between the types of foetal hypoxia (acute, subacute, evolving, chronic), as identified on cardiotocography and the nature of hypoxic ischaemic encephalopathy, as observed on MRI scans after birth. We conducted a retrospective study of 16 babies born (out of 52,187 births) at St George's Hospital in London during 2006-2017 with a postnatal diagnosis of HIE. Of the 16 babies, only 11 had both MRI scans and CTG traces available. Of those, 9 showed evidence of intrapartum hypoxia on CTG, but only 6 demonstrated evidence of HIE on MRI. Those with acute hypoxia showed abnormalities in the basal ganglia and thalami. A gradually evolving hypoxia or subacute hypoxia was associated with lesions in myelination and cerebral cortex.Impact StatementWhat is already known on this subject? It has been reported that inter-observer agreement for CTG interpretation is low (30%) when pattern recognition based guidelines are used (Rhöse et al. 2014; Reif et al. 2016), even amongst 'experts' (Hruban et al. 2015). Furthermore, it has been shown that CTG traces do not reliably predict neonatal encephalopathy (Spencer et al. 1997).What do the results of this study add? Our study indicates that if 'types of intrapartum hypoxia' are used for interpretation, then inter-observer agreement increases to 81%, from the reported 30% when traces are classified into 'normal, suspicious and pathological' using guidelines based on 'pattern recognition'. Furthermore, our study shows a good correlation between the type of intrapartum hypoxia observed on CTG trace and the nature of injury observed on the MRI.What are the implications of these findings for clinical practise and/or further research? Improving inter-observer agreement of CTGs with the use of pattern recognition in combination with the good correlation to MRI scan findings ultimately leads to better management and post-natal outcomes. This is evidenced by the fact that after the introduction of physiology-based CTG interpretation and mandatory competency testing on CTG interpretation for all staff in 2010, St. George's Maternity Unit has half the nationally reported rate of cerebral palsy.

Intrapartum cardiotocography patterns observed in suspected clinical and subclinical chorioamnionitis in term fetuses.

AIM: To evaluate the cardiotocography (CTG) features observed in suspected intrapartum chorioamnionitis in term fetuses according to the recently suggested criteria for the pathophysiological interpretation of the fetal heart rate and their correlation with perinatal outcomes. METHODS: Retrospective analysis of nonconsecutive CTG traces. 'CTG chorioamnionitis' was diagnosed either based on a persistent rise in the baseline for the given gestation or on a persistent increase in the baseline fetal heart rate during labor >10% without preceding CTG signs of hypoxia and in the absence of maternal pyrexia. Perinatal outcomes were compared among cases with no sign of chorioamnionitis, in those with only CTG features suspicious for chorioamnionitis and in those who developed clinical chorioamnionitis. RESULTS: Two thousand one hundred and five CTG traces were analyzed. Of these, 356 fulfilled the criteria for "CTG chorioamnionitis". Higher rates of Apgar <7 at 1 and 5 min (21.6% vs 9.0% and 9.8% vs 2.0%, respectively, P < 0.01 for both) and lower umbilical artery pH (7.14 ± 0.11 vs 7.19 ± 0.11, P < 0.01) and an over fivefold higher rate of neonatal intensive care unit admission (16.6% vs 2.9%, P < 0.01) were noted in the 'CTG chorioamnionitis' group. Differences in the incidence of abnormal CTG patterns were noted between cases who eventually had clinical evidence of chorioamnionitis (89/356) and those showing CTG features suspicious for chorioamnionitis in the absence of clinical evidence of chorioamnionitis (267/356). CONCLUSION: Intrapartum CTG features of suspected chorioamnionitis are associated with adverse perinatal outcomes.