Fetal heart rate classification proposed by the perinatology committee of the Japan Society of Obstetrics and Gynecology: reproducibility and clinical usefulness

Correlation between the 5-tier fetal heart rate pattern classification at delivery and Apgar scores

AIM

In Japan, the fetal heart rate pattern on cardiotocography is usually categorized into five levels for intrapartum management; however, studies on the 5-tier cardiotocography classification are limited. This study aimed to determine the correlation between 5-tier cardiotocography levels at delivery, neonatal Apgar scores and perinatal prognosis using a perinatal registry database.

METHODS

This retrospective study used the 2018 Perinatal Registry Database of the Japan Society of Obstetrics and Gynecology. Apgar scores and perinatal prognosis were compared between patients with Japan Society of Obstetrics and Gynecology intrapartum cardiotocography levels 1-2, and levels 3-5.

RESULTS

In total, 240 987 cases were registered, with 114 201 full-term deliveries comprising 84 703 vaginal and 29 498 cesarean deliveries. For vaginal delivery cases, the crude odds ratios of 1-min Apgar score ≤3 for levels 3 (odds ratio: 1.7, 95% confidence interval: 1.4-2.0, p < 0.0001), levels 4 (odds ratio: 5.9, 95% confidence interval: 5.1-6.9, p < 0.0001), and levels 5 (odds ratio: 49.2, 95% confidence interval: 37.5-64.5, p < 0.0001) were significantly higher than those for levels 1-2 (odds ratio: 1.0). Moreover, the crude odds ratios of 5-min Apgar score ≤ 3 for levels 4 (odds ratio: 4.8, confidence interval: 2.7-8.7, p < 0.0001), and levels 5 (odds ratio: 71.1, confidence interval: 32.6-155.1, p < 0.0001) were significantly higher than those for levels 1-2 (odds ratio: 1.0). Similarly, in cases of cesarean delivery, it showed a similar trend to case of vaginal delivery cases.

CONCLUSION

The 5-tier cardiotocography classification can predict severe neonatal asphyxia.

iPREFACE score: Integrated score index to predict fetal acidemia by intrapartum fetal heart rate monitoring

AIM

Cardiotocography is used worldwide to evaluate fetal well-being during pregnancy and labor. In past guidelines, the management plan was determined based on the assessment of the most severe waveform. There are no guidelines for evaluating the integrated recurrent decelerations; however, we believe their assessment to be essential for predicting the status of the fetus. The objective of this study was to propose an indicator for performing medical interventions during labor by creating a scoring system that reflects integrated recurrent decelerations.

METHODS

In this retrospective cohort study, we included data for only full-term single fetus births from vaginal deliveries. The score named the iPREFACE score (integrated score index to predict fetal acidemia by intrapartum fetal heart rate monitoring) was calculated using cardiotocography findings from continuing 30 min before delivery. We examined the iPREFACE score and fetal acidemia association and calculated the cut-off iPREFACE scores for acidemia using receiver operating characteristic curves.

RESULTS

The study included 469 delivery cases. Their iPREFACE scores exhibited a significant negative correlation with the umbilical artery blood pH (correlation coefficient; -0.43). The cut-off iPREFACE scores for the umbilical artery blood with pH <7.20, <7.10 and <7.0 were 44, 46 and 67, respectively (the areas under the curve were 0.776, 0.962 and 0.996, respectively).

CONCLUSION

The iPREFACE score may predict fetal acidemia and could be used as an indicator for timely medical interventions during labor. Because assessments using a cardiotocography are quick and easy to perform, the iPREFACE score could be a valuable tool in clinical practice.

Accuracy of predicting neonatal distress using a five-level classification of fetal heart rate monitoring

AIM

To assess the accuracy of neonatal distress prediction using the five-level classification of fetal heart rate (FHR) and management protocol of the Japan Society of Obstetrics and Gynecology (JSOG).

METHODS

A case-control study was conducted. Vertex singleton pregnant women who delivered after 37 weeks' gestation from 2013 to 2015 were enrolled. The participants were categorized into two groups; controls were levels 1-3 (n = 1184), whereas cases were levels 4-5 (n = 117) group. Neonatal distress was defined as Apgar score < 8 points at 5 min or umbilical cord artery pH < 7.1.

RESULTS

There were 117 cases (9.0%). The frequency of the neonatal distress was observed in 1.3% controls and 6.8% cases (P < 0.01). Diagnostic accuracy of neonatal distress for cases showed a 6.8% positive-predictive value, 34.8% sensitivity, 91.5% specificity and 98.7% negative-predictive value. Among various obstetrical conditions, high sensitivity (100%) for prediction of neonatal distress was observed in women with chromosome abnormalities, placental abruption, umbilical cord abnormalities and excessive labor pain. Conversely, relatively low specificity (<50%) was observed in cases with oligohydramnios and excessive labor pain.

CONCLUSION

The five-level classification scheme was efficient for neonatal distress prediction. However, depending on the obstetric condition, the FHR findings and neonatal condition might be independent.

Association between exposure to air pollution during pregnancy and false positives in fetal heart rate monitoring

Fetal heart rate (FHR) monitoring is essential for fetal management during pregnancy and delivery but results in many false-positive diagnoses. Air pollution affects the uterine environment; thus, air pollution may change FHR reactivity. This study assessed the association between exposure to air pollution during pregnancy and FHR monitoring abnormalities using 2005-2010 data from the Japan Perinatal Registry Network database. Participants were 23,782 singleton pregnant women with FHR monitoring, without acidemia or fetal asphyxia. We assessed exposure to air pollutants, including particulate matter (PM), ozone, nitrogen dioxide (NO2), and sulfur dioxide (SO2). In a multi-trimester model, first-trimester PM exposure was associated with false positives in FHR monitoring (odds ratio [OR] per interquartile range (10.7 μg/m3) increase = 1.20; 95% CI: 1.05-1.37), but not second-trimester exposure (OR = 1.05; 95% CI: 0.91-1.21) and third-trimester exposure (OR = 1.06; 95% CI: 0.96-1.17). The association with first-trimester PM exposure persisted after adjustment for exposure to ozone, NO2, and SO2; however, ozone, NO2, and SO2 exposure was not associated with false positives in FHR monitoring. First-trimester PM exposure may alter fetal cardiac response and lead to false positives in FHR monitoring.

Reliability in cardiotocography interpretation - impact of extended on-site education in addition to web-based learning: an observational study

INTRODUCTION

Previous studies have shown poor reproducibility in cardiotocography (CTG) interpretation. Studies evaluating the Swedish web-based CTG-education program have not proven to increase accurate CTG assessments. The aim of this study was to evaluate whether an extended education can improve inter- and intra-observer reliability in CTG interpretation.

MATERIAL AND METHODS

Six obstetricians from two different departments interpreted 106 CTG tracings on two occasions. Both departments used a Swedish national web-based CTG education and test for training. One department had, in addition, an extended education program consisting of on-site lectures and oral examinations. Inter- and intra-observer agreements were calculated by simple or weighted kappa (κ) values for the five parameters assessed on CTG.

RESULTS

In both departments inter-observer and intra-observer κ showed moderate to excellent agreement (ranges for κ 0.41-0.76 and 0.65-0.93, respectively). Obstetricians at the department with extended CTG education had better inter-observer reliability for variability and accelerations. This was also the case for intra-observer reliability with the addition of baseline frequency. Both inter- and intra-observer agreement increased from moderate to substantial in both departments when decelerations were dichotomized into harmless (including early and simple variable decelerations) or hypoxic (including late, severe variable, prolonged and combined decelerations) (κ 0.63-0.78) compared with the current sub-classification of decelerations (κ 0.42-0.65).

CONCLUSIONS

Agreement in CTG interpretation was better than expected in both departments, especially when divided into harmless/hypoxic changes. Combination of different learning methods (web-based, on-site lectures and case discussion) might result in a better CTG interpretation agreement compared with web-based learning solely.

Absence of accelerations during labor is of little value in interpreting fetal heart rate patterns

INTRODUCTION

The aim of this study was to investigate the correlation between increasing time since fetal heart rate (FHR) accelerations, positive (no acceleration) stimulation tests and fetal acidemia.

MATERIAL AND METHODS

Observational study of FHR recordings from 1070 laboring women with indication for fetal scalp blood sampling (FBS). FHR traces were scrutinized regarding acceleration at FBS and duration since most recent acceleration. The appraiser was blinded to the FBS result.

RESULTS

At the first sampling, 8.8% of fetuses had lactate concentration >4.8 mmol/L. There were no differences between those with recent accelerations (≤60 min), and absent accelerations (>60 min or never) prior to FBS (8.3% vs. 8.9%, p = 0.71). Corresponding analyses for subgroups were: fetuses with isolated absence of accelerations, 3.7% vs. 1.5% (p = 0.41), fetuses without decelerations (i.e. reduced variability and/or tachycardia), 6.1% vs. 5.1% (p = 0.81) and fetuses with serious decelerations (i.e. late or complicated variable), 15.0% vs. 16.1% (p = 0.87). Among fetuses with serious decelerations, increasing duration from most recent acceleration had a weak but statistically significant correlation to increased lactate concentration (rs = 0.12, p = 0.03). The positive likelihood ratio for acidemia with no response at FBS was 1.15.

CONCLUSION

In a population with FBS performed upon indication, there was no correlation between duration since last FHR acceleration and increased lactate concentration. The majority of fetuses are not acidemic even when the FHR trace is pathological and stimulation tests are only helpful when accelerations are provoked.