Double-to-Single Umbilical Artery With a Low Pulsatility Index Leading to Fetal Death: A Case Report and Review of Literature.

Single umbilical artery (SUA) may be associated with adverse pregnancy outcomes, such as fetal death, emergency cesarean section, premature delivery, small-for-gestational-age infants, and admission to neonatal intensive care unit, and some SUAs are transformed from originally double umbilical arteries (UA). The pulsatility index (PI) can reflect the resistance of UA, and clinicians attach importance to high PI but easily overlook low levels of it. We reported one case of a pregnant woman who underwent double to single UA accompanied by low UA-PI and finally had intrauterine fetal death. Additionally, the literature regarding SUA and UA-PI is reviewed. This study aims to alert clinicians to the risk of double-to-single UA with low UA-PI and strengthen fetal monitoring and timely intervention. We look forward to more clinical evidence to investigate it.