ADHD risk linked to birth apgar score and cord pH combined

Credit: Pixelistanbul

By Olivia Bowthorpe

Low oxygen levels at the time of birth may be linked to a higher risk of ADHD, but only when both clinical and biochemical evidence of hypoxia are present together.

A large Danish study reveals the chances of the disorder rises by 86% when newborns experience both low Apgar scores and low umbilical cord blood pH,

This finding, published in JAMA Network Open, suggests that relying on the Apgar score (Appearance, Pulse, Grimace, Activity, and Respiration) alone may overestimate the role of perinatal hypoxia in ADHD risk.

Researchers found that when either measure was normal, the risk of ADHD did not increase, suggesting that many children currently flagged as at-risk based on a single measure may not face elevated ADHD risk at all.

"A low Apgar score from other causes than perinatal hypoxia, such as disease that may exist before birth or maternal drug exposure, may be benign if handled appropriately," write Dr Mette Vestergard Pedersen, MD in clinical medicine at Aarhus University Hospital, Denmark, and colleagues in JAMA Network Open.

"Reporting increased risk of ADHD from such benign causes may lead to unnecessary concern in parents and health care personnel," they add.

The team analysed nationwide registry data on 819,658 singleton infants born between 2004 and 2018. All were born at 35 weeks’ gestation or afterwards and followed until the end of 2022.

ADHD was identified via hospital diagnoses and prescriptions for ADHD drugs. Perinatal hypoxia was assessed from the five-minute Apgar score and umbilical cord blood pH.

Later risk of ADHD was increased only in those with both a low five-minute Apgar score and a low pH. The highest risk was for infants with an Apgar score of three or below plus a pH below 7.10. This group had an 86% higher odds of ADHD.

"If the Apgar score was low and the pH level was normal, or vice versa, we observed no association with ADHD," the authors write, adding: "Children should not be followed up for behavioral symptoms based only on their Apgar score or their umbilical cord blood pH."

Although the relative risk of ADHD was higher when both measures were abnormal, the authors point out that the absolute risk was low, and that perinatal hypoxia is likely to be just one of many factors contributing to ADHD.

"These findings are important as they may reduce anxiety in the parents of these large groups of children," they conclude.

Reference: JAMA Netw Open DOI: 10.1001/jamanetworkopen.2025.54672

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