INTRODUCTION: We aimed to clarify whether the coagulation-fibrinolytic system is activated in a hyper-coiled umbilical cord (HCC). METHODS: This prospective cohort study was conducted at a single perinatal center in Japan, including singleton pregnant women who delivered after 37 weeks of gestation between January and July 2024. Umbilical venous blood was collected immediately after birth and before placental delivery. The coagulation and fibrinolytic systems were measured, and variables were compared between patients with and without HCC. RESULTS: As a variable of cell blood count and hemostatic function, platelet concentration was significantly lower in the HCC group [median (range): 25.5 (17.3-32.1) vs 30.4 (18.5-39.55) x100000/μl, p = 0.020]. For coagulation variables, fibrinogen concentration [105 (63-116) vs 137.5 (56-229) mg/dl, p <
0.001] and antithrombin III [35 (27-51) vs 47.5 (31-62) %, p = 0.022] were significantly lower in the HCC group. Regarding fibrinolytic variables, plasmin inhibitor complex concentration was significantly higher in HCC group [1.3 (1.0-6.9) vs 0.7 (0.3-5.2) μg/ml, p = 0.036]
however, plasminogen concentration was significantly lower in HCC group [40 (32-46) vs 50 (25-64), p <
0.001]. DISCUSSION: This is the first report where the coagulation-fibrinolytic system in the umbilical venous blood in cases with HCC was demonstrated. Findings reveal an activated coagulation-fibrinolytic system even in cases without severe fetal growth restriction due to HCC after 37 weeks of gestation.