Discordancy of pH value between two umbilical arteries at delivery

To evaluate the difference in pH values between the two umbilical arteries at delivery and identify obstetric factors influencing this discordance.

This single-center observational study included 166 deliveries at Shiga University of Medical Science Hospital between April 2020 and October 2021. Paired umbilical artery blood samples were collected at delivery, and their pH values were analyzed. Regression analyses were conducted to identify factors associated with pH discordance, including fetal growth restriction (FGR), birth weight Z-score, and umbilical artery Doppler abnormalities.

Key factors significantly associated with greater pH discordance included lower birth weight Z-score (p = 0.0268), reverse or absent diastolic flow in one umbilical artery (p = 0.0060), and lower minimum pH values (p = 0.0115). The maximum observed pH difference is 0.086. Scatterplots highlighted greater discordance in cases with Doppler abnormalities or the abovementioned three conditions.

This study demonstrated that discordance in pH values between umbilical arteries can occur under specific conditions such as lower Z-scores of birth weight or pH values, and umbilical artery Doppler abnormalities. These findings suggest the need for dual artery sampling in high-risk cases to ensure an accurate evaluation of fetal acid-base status.