Umbilical artery thrombosis diagnosed by fetal ultrasound.

Umbilical artery thrombosis (UAT) is a rare and severe condition associated with grave perinatal outcomes, including intrauterine fetal death. This case report presents the case of a 38-year-old woman (gravida 3, para 1) of Japanese ethnicity, with a history of one spontaneous miscarriage, who conceived through micro-insemination and blastocyst transfer. Initial patient screening at 30 weeks and 6 days of gestation revealed normal fetal development, with two umbilical arteries and one umbilical vein. However, at 34 weeks and 5 days of gestation, we observed reduced fetal movements and the absence of accelerations on cardiotocography. Subsequent color Doppler examination revealed cessation of blood flow across a broad area in one umbilical artery and a strongly curved umbilical vein surrounding the blood flow of the other artery. These formed the 'orange grab sign,' suggestive of UAT. Evaluations of blood flow in other areas revealed unremarkable findings. We performed an emergency cesarean section owing to fetal distress. The mother and newborn were healthy and discharged as healthy. The 1-month check-up revealed no abnormalities in the child. Pathological examination of the umbilical cord revealed fibrin-based thrombus formation along the length of one artery, confirmed to be an umbilical artery. In the present case report, we presented the diagnostic challenges of UAT. Furthermore, we highlighted the need for timely intervention by comparing the number of umbilical vessels among previous ultrasound findings and verifying the presence of the 'orange grab sign.'