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

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.

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.

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.

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