Unfavorably altered fibrin clot properties in women with unexplained infertility: association with pregnancy outcomes

Abstract Objectives Ovarian stimulation (OS) and pregnancy were shown to be associated with a prothrombotic state. We sought to determine whether a positive pregnancy outcome is related to fibrin clot properties and thrombin generation in women with unexplained infertility (UI) after OS followed by intrauterine insemination (IUI). Methods We studied 70 women with UI, aged 30.7 ± 3.5 years, BMI 24.7 ± kg/m2 together with 70 controls who had healthy births matched for age and weight. We measured thrombin generation capacity, plasma fibrin clot permeability (Ks), and fibrinolytic potential (clot lysis time, CLT). In women with UI, after OS followed by IUI, pregnancy outcomes were recorded. Results UI women had prolonged lag time (+ 10.0%) and lower thrombin generation reflected by ETP (−17.8%) and formed clots less permeable (− 20.8%; Ks) and more resistant to lysis (+ 17.5% CLT) compared to controls (all p < 0.05). Women with UI and positive pregnancy outcome (n = 19, 27.1%) showed increased KS (+ 67.9%) along with shorter CLT (− 15.9%) with no difference in thrombin generation, when compared to non-pregnant women. In women with UI ETP was associated with peak thrombin (r = 0.57, p = 0.02), whereas CLT was negatively correlated both with KS (r = − 0.42, p = 0.001) and TSH (r = − 0.56, p = 0.04). Conclusions Women with UI display unfavorably modified fibrin clot properties, especially those with negative pregnancy outcomes, which suggests the impact of fibrin clot characteristics on treatment results.