Physiological cardiotocography interpretation and neonatal morbidity: A historical pre–post cohort study in a tertiary perinatal center

INTRODUCTION: Cardiotocography (CTG) interpretation is prone to inter-observer variability and may contribute to both missed fetal compromise and potentially avoidable intrapartum intervention. Physiological CTG interpretation (PCI) reframes fetal surveillance around fetal physiology and the intensity of hypoxic stress, but real-world outcome data after unit-wide implementation remain limited. MATERIAL AND METHODS: Historical pre-post cohort study with case-mix adjustment at University Hospital Ulm, a tertiary perinatal center in Germany (~3200 births/year). We included term singleton pregnancies (≥37 + 0 weeks) with intended vaginal birth, comparing a pre-implementation period (January 01-December 31, 2018) with a post-implementation period after full adoption (May 01, 2022-April 30, 2023). PCI was introduced as a multicomponent implementation strategy (training, bedside facilitation, documentation changes, and sustainment). PRIMARY OUTCOME: composite neonatal morbidity defined as neonatal unit (NNU) transfer plus ≥1 of: umbilical artery pH <7.15, base deficit >16 mmol/L, or 5-min Apgar score <7. SECONDARY OUTCOMES: umbilical artery acid-base status, Apgar scores, NNU transfer, intrapartum interventions (e.g., oxytocin, tocolysis, fetal scalp blood sampling), mode of birth, and postpartum blood loss. Outcomes were compared using multivariable regression and propensity score matching. RESULTS: A total of 4484 births met the inclusion criteria (2352 pre-implementation; 2132 post-implementation). Composite neonatal morbidity decreased from 4.10% to 2.92% (OR 0.67; 95% CI 0.434-0.958; p = 0.0259). Neonatal acidosis decreased (umbilical artery pH <7.10: 3.87%-2.53%; OR 0.649; 95% CI 0.450-0.919; p = 0.014), and NNU transfers declined (13.18%-9.19%; OR 0.667; 95% CI 0.59-0.808; p < 0.001). Cesarean section rates were not increased after adjustment (OR 0.880; 95% CI 0.722-1.071). Postpartum blood loss was higher post-implementation (438 vs 497 mL; p < 0.001). CONCLUSIONS: Unit-wide implementation of PCI was associated with improved neonatal outcomes, including fewer NNU admissions, without an increase in adjusted cesarean section rates. These findings support PCI as a promising framework for intrapartum fetal surveillance, warranting confirmation in multicenter studies and evaluation across different care settings.