New possibilities for ST analysis - A post-hoc analysis on the Dutch STAN RCT.

BACKGROUND: The diagnostic value of ST analysis of the fetal electrocardiogram (fECG) during labor is uncertain. False alarms (ST events) may be explained by physiological variation of the fetal electrical heart axis. Adjusted ST events, based on a relative rather than an absolute rise from baseline, correct for this variation and may improve the diagnostic accuracy of ST analysis. AIMS: Determine the optimal cut-off for relative ST events in fECG to detect fetal metabolic acidosis. STUDY DESIGN: Post-hoc analysis on fECG tracings from the Dutch STAN trial (STAN+CTG branch). SUBJECTS: 1328 term singleton fetuses with scalp ECG tracing during labor, including 10 cases of metabolic acidosis. OUTCOME MEASURES: Cut-off value for relative ST events at the point closest to (0,1) in the receiver operating characteristic (ROC) curve with corresponding sensitivity and specificity. RESULTS: Relative baseline ST events had an optimal cut-off at an increment of 85% from baseline. Relative ST events had a sensitivity of 90% and specificity of 80%. CONCLUSIONS: Adjusting the current definition of ST events may improve ST analysis, making it independent of CTG interpretation.

Heart rate variability in hypertensive pregnancy disorders: A systematic review.

BACKGROUND: Hypertensive pregnancy disorders (HPD) are associated with dysfunction of the autonomic nervous system. Cardiac autonomic functions can be assessed by heart rate variability (HRV) measurements. OBJECTIVE: To study whether HRV detects differences in the function of the autonomic nervous system between pregnant women with HPD compared to normotensive pregnant women and between women with a history of a pregnancy complicated by HPD compared to women with a history of an uncomplicated pregnancy. METHODS: A systematic search was performed in Medline, EMBASE, and CENTRAL to identify studies comparing HRV between pregnant women with HPD or women with a history of HPD to women with (a history of) normotensive pregnancies. RESULTS: The search identified 523 articles of which 24 were included in this review, including 850 women with (a history of) HPD and 1205 normotensive controls. The included studies showed a large heterogenicity. A decrease in overall HRV was found in preeclampsia (PE), compared to normotensive pregnant controls. A trend is seen towards increased low frequency/high frequency-ratio in women with PE compared to normotensive pregnant controls. CONCLUSION: Our systematic review supports the hypothesis a sympathetic overdrive is found in HPD which is associated with a parasympathetic withdrawal. However, the included studies in our review showed a large diversity in the methods applied and their results.

Is intrapartum fever associated with ST-waveform changes of the fetal electrocardiogram? A retrospective cohort study.

OBJECTIVE: To investigate the association between maternal intrapartum fever and ST-waveform changes of the fetal electrocardiogram. DESIGN: Retrospective cohort study. SETTING: Three academic and six non-academic teaching hospitals in the Netherlands. POPULATION: Labouring women with a high-risk singleton pregnancy in cephalic position beyond 36 weeks of gestation. METHODS: We studied 142 women with fever (≥38.0°C) during labour and 141 women with normal temperature who had been included in two previous studies. In both groups, we counted the number and type of ST-events and classified them as significant (intervention needed) or not significant, based on STAN(®) clinical guidelines. MAIN OUTCOME MEASURES: Number and type of ST-events. RESULTS: Both univariable and multivariable regression analysis showed no association between the presence of maternal intrapartum fever and the number or type of ST-events. CONCLUSIONS: Maternal intrapartum fever is not associated with ST-segment changes of the fetal electrocardiogram. Interpretation of ST-changes in labouring women with fever should therefore not differ from other situations.

A clinical prediction model to assess the risk of operative delivery.

OBJECTIVE: To predict instrumental vaginal delivery or caesarean section for suspected fetal distress or failure to progress. DESIGN: Secondary analysis of a randomised trial. SETTING: Three academic and six non-academic teaching hospitals in the Netherlands. POPULATION: 5667 labouring women with a singleton term pregnancy in cephalic presentation. METHODS: We developed multinomial prediction models to assess the risk of operative delivery using both antepartum (model 1) and antepartum plus intrapartum characteristics (model 2). The models were validated by bootstrapping techniques and adjusted for overfitting. Predictive performance was assessed by calibration and discrimination (area under the receiver operating characteristic), and easy-to-use nomograms were developed. MAIN OUTCOME MEASURES: Incidence of instrumental vaginal delivery or caesarean section for fetal distress or failure to progress with respect to a spontaneous vaginal delivery (reference). RESULTS: 375 (6.6%) and 212 (3.6%) women had an instrumental vaginal delivery or caesarean section due to fetal distress, and 433 (7.6%) and 571 (10.1%) due to failure to progress, respectively. Predictors were age, parity, previous caesarean section, diabetes, gestational age, gender, estimated birthweight (model 1) and induction of labour, oxytocin augmentation, intrapartum fever, prolonged rupture of membranes, meconium stained amniotic fluid, epidural anaesthesia, and use of ST-analysis (model 2). Both models showed excellent calibration and the receiver operating characteristics areas were 0.70-0.78 and 0.73-0.81, respectively. CONCLUSION: In Dutch women with a singleton term pregnancy in cephalic presentation, antepartum and intrapartum characteristics can assist in the prediction of the need for an instrumental vaginal delivery or caesarean section for fetal distress or failure to progress.

Fetal blood sampling in addition to intrapartum ST-analysis of the fetal electrocardiogram: evaluation of the recommendations in the Dutch STAN® trial.

OBJECTIVES: To evaluate the recommendations for additional fetal blood sampling (FBS) when using ST-analysis of the fetal electrocardiogram. DESIGN: Prospective cohort study. SETTING: Three academic and six non-academic teaching hospitals in the Netherlands. POPULATION: Labouring women with a high-risk singleton pregnancy in cephalic position beyond 36 weeks of gestation. METHODS: In labouring women allocated to the STAN® arm of a previously published randomised controlled trial who underwent one or more FBS during delivery, we assessed whether FBS was performed according to the trial protocol and how fetal acidosis, defined as an FBS pH < 7.20, was related to ST-waveform analysis. MAIN OUTCOME MEASURES: The number of FBS showing fetal acidosis, related to the different STAN® criteria where additional FBS is recommended. RESULTS: Among 2827 women monitored with STAN®, 297 underwent FBS, of whom 171 (57.6%) were performed according to the predefined criteria and 126 were performed in absence of these criteria. In the first group, rates of fetal acidosis (pH < 7.20) were two of 18, none of nine, 12 of 111 and three of 33 when FBS was taken for abnormal cardiotocogram (CTG) at the start, intermediary CTG at the start, abnormal CTG >60 minutes, and poor electrocardiogram quality, respectively. When the predefined criteria were not met and ST-analysis showed no ST-events, only two incidents of fetal acidosis were seen. CONCLUSIONS: The performance of FBS is valuable in the advised STAN® criteria. When these criteria are not met, performance of FBS does not seem helpful in the detection of fetal acidosis.

Inter- and intra-observer agreement of intrapartum ST analysis of the fetal electrocardiogram in women monitored by STAN.

OBJECTIVE: The objective of this study was to quantify inter- and intra-observer agreement on classification of the intrapartum cardiotocogram (CTG) and decision to intervene following STAN guidelines. DESIGN: A prospective, observational study. SETTING: Obstetrics Department of a tertiary referral hospital. POPULATION: STAN recordings of 73 women after 36 weeks of gestation with a high-risk pregnancy, induced or oxytocin-augmented labour, meconium-stained amniotic fluid or epidural analgesia. METHODS: Six observers classified 73 STAN recordings and decided if and when they would suggest an intervention. Proportions of specific agreement (Ps) and kappa values (Kappa) were calculated. MAIN OUTCOME MEASURES: Agreement upon classification of the intrapartum CTG and decision to perform an intervention. RESULTS: Agreement for classification of a normal and a (pre)terminal CTG was good (Ps range 0.50-0.84), but poor for the intermediary and abnormal CTG (Ps range 0.34-0.56). Agreement on the decision to intervene was higher, especially on the decision to perform 'no intervention' (Ps range 0.76-0.94). Overall inter-observer agreement on the decision to intervene was considered moderate in five of six observer combinations according to the kappa (Kappa range 0.42-0.73). Intra-observer agreement for CTG classification and decision to intervene was moderate (Kappa range 0.52-0.67 and 0.61-0.75). CONCLUSIONS: Inter-observer agreement on classification of the intrapartum CTG is poor, but addition of information regarding fetal electrocardiogram, especially in case of intermediary or abnormal CTG traces, results in a more standardised decision to intervene.

Limitations of ST analysis in clinical practice: three cases of intrapartum metabolic acidosis.

OBJECTIVE: To examine detailed intrapartum events in cases of neonatal metabolic acidosis despite monitoring using STAN (cardiotocography [CTG] plus ST waveform analysis of fetal electrocardiogram [ECG]). DESIGN: Retrospective case review. SETTING: High-risk pregnancies monitored by STAN. METHODS: Case note review was performed in newborns with metabolic acidosis where no significant ST changes in the fetal ECG occurred prior to birth. MAIN OUTCOME MEASURES: Metabolic acidosis. RESULTS: Detailed review of three cases identified poor signal quality, difficulties in CTG interpretation, failure to comply with STAN clinical guidelines and deterioration of the CTG without ECG alert as the leading causes of these adverse outcomes. CONCLUSIONS: The cases illustrate some of the pitfalls associated with the clinical application of the STAN technology which prevent severe metabolic acidosis being eradicated completely. It may be useful to expand the STAN guidelines protocol towards the identification of exceptional clinical situations, such as in our cases, and towards appropriate additional interventions, as this may lead to a further reduction in adverse neonatal outcomes.