Intrapartum cardiotocographic patterns and perinatal outcomes in extremely preterm births: an exploratory retrospective cohort study

Extremely preterm birth (24–28 weeks of gestation) carries high perinatal risk. While intrapartum cardiotocography (CTG) is routinely used at term, its interpretation in extremely preterm birth remains unclear. This study aims to explore the relationship between intrapartum CTG characteristics and perinatal outcomes in extremely preterm birth. An exploratory retrospective cohort study, part of the NIEM-O study, was conducted at the Obstetrics Department of a tertiary referral hospital. Intrapartum CTG recordings of 73 women with a spontaneous onset of birth between 24 and 28 weeks of gestation were included. Signal loss (n = 73) and CTG characteristics during the last hour of the first stage of labor (n = 55), and during second stage of labor (n = 24) were assessed using computerized analysis. CTG characteristics (baseline fetal heart rate, heart rate variability, accelerations, decelerations, uterine contractions, and combinations of these characteristics) were compared between fetuses with neonatal outcome of low 5-minute Apgar score (< 7) and a group with 5-minute Apgar score > 7. CTG tracings in preterm fetuses frequently displayed recognizable features, including baseline variability (median 18 bpm) and both accelerative (median five/hour) and decelerative (median 11/hour) responses. Preterm fetuses with a low 5-minute Apgar score (n = 20) exhibited significantly more variable decelerations (median 14/hour vs. six/hour) and uterine contractions (19/hour vs. 13/hour), compared to those without this outcome. CTG characteristics commonly described as indicators of hypoxia in term fetuses were not consistently observed in the studied preterm population. Although CTG features were often identifiable in preterm fetuses, their presentation differed from those commonly described at term, particularly in those with low 5-minute Apgar score. These findings highlight the need for gestational age-specific CTG reference ranges. Adapting CTG interpretation to reflect the unique physiology of this group is essential for improving timely clinical decision-making and reducing perinatal morbidity and mortality. Registered on 22 November 2023 in Clinicaltrails.gov (Number: NCT06151613) via https://clinicaltrials.gov/study/NCT06151613 and on 18 October 2022 to the Central Committee on Research Involving Human Subjects (NL82869.015.22).