This study aims to improve understanding of how fetuses respond to oxygen deprivation during labor by re-evaluating cardiotocography (CTG) recordings using a physiology-based interpretation approach and comparing these findings with umbilical cord blood gas measurements at birth, including eucapnic pH assessment.

The study will include term pregnancies and combines retrospective data analysis with prospective enrollment. Researchers will investigate whether physiology-based CTG interpretation can better identify signs of fetal compromise and whether eucapnic pH may improve the distinction between respiratory and metabolic acidosis. Findings may contribute to improving fetal monitoring strategies and the assessment of newborn condition at birth.

Cardiotocography (CTG) is widely used for intrapartum fetal surveillance; however, traditional pattern-recognition approaches may not always reflect the underlying fetal physiological response to hypoxic stress. Recently, physiology-based CTG interpretation frameworks have been proposed to improve identification of fetal compensation and decompensation mechanisms during labor.

Similarly, conventional interpretation of umbilical cord blood gas analysis may not adequately distinguish respiratory from metabolic components of neonatal acidemia. Eucapnic pH, calculated by correcting for the respiratory component of acid-base imbalance, has been proposed as a tool to better characterize metabolic compromise at birth.

This ambispective observational study aims to re-evaluate CTG tracings obtained during labor using a physiology-based interpretative framework and to integrate these findings with arterial umbilical cord blood gas parameters, including measured pH, base excess, pCO2, and calculated eucapnic pH.

The study includes a retrospective cohort of term singleton deliveries and a prospective cohort of consecutively enrolled term pregnancies undergoing intrapartum CTG monitoring. CTG recordings will undergo blinded re-evaluation by independent reviewers using physiology-based criteria. These findings will be integrated with maternal, intrapartum, and neonatal variables to explore relationships between CTG characteristics, types of hypoxic exposure, acid-base status, and neonatal outcomes.

The study aims to determine whether physiology-based CTG interpretation identifies fetal compromise not recognized using conventional interpretation methods and to evaluate the relationship between CTG findings, eucapnic pH, and neonatal condition at birth. The results may contribute to improving understanding of intrapartum fetal adaptation and refining strategies for fetal surveillance during labor.

Inclusion Criteria:

• Singleton pregnancies

• Term neonates (gestational age =or> 37 weeks)

• Availability of clinical data, such as

  • CTG tracing within 90 minutes before delivery
  • Umbilical cord blood gas analysis (arterial sample)

• Signed informed consent (only for the prospective arm)

Exclusion Criteria:

• Major fetal anomalies
• Incomplete or missing CTG or blood gas data
• Elective cesarean sections without labor

Only females are eligible because the study population consists of pregnant women undergoing labor and delivery. The study evaluates intrapartum cardiotocography findings, labor characteristics, and neonatal outcomes associated with pregnancy and childbirth.

The study population consists of women with term singleton pregnancies undergoing labor and delivery at a tertiary referral center. The study includes both retrospectively identified deliveries and prospectively enrolled pregnancies with available intrapartum cardiotocography (CTG) recordings and umbilical cord arterial blood gas analysis.

Individual participant data (IPD) will not be shared because the study involves retrospective and prospective collection of sensitive clinical and perinatal data, and data sharing may not be compatible with institutional policies, participant privacy protection, and applicable data protection regulations.