Cerebral Palsy Risk by Combined Apgar Score and Umbilical Cord Blood pH Levels

Importance: Perinatal hypoxia is an important cause of cerebral palsy (CP). Although criteria for relevant perinatal hypoxia require both clinical and biochemical abnormalities, such as low Apgar score and low umbilical cord blood pH, most observational studies have considered only 1 of these measures. Objective: To investigate the association of perinatal hypoxia assessed by Apgar score combined with umbilical cord blood pH with CP. Design, Setting, and Participants: This registry-based cohort study was conducted nationwide in Denmark with follow-up until December 31, 2022. Analyses were performed from October 2024 to May 2025. All singleton newborns with a gestational age of 35 weeks or older without major malformations between January 1, 2004, and December 31, 2018, with at least 1 year of follow-up were included. Exposure: Combinations of 5-minute Apgar score category (0-3, 4-6, and 7-10) and umbilical cord blood pH category (