The mechanisms responsible for pregnancy loss have not all been elucidated. CD146 is a cell adhesion molecule involved in the control of both endothelium integrity and intermediate trophoblast invasiveness, two potential key features in the pathogenesis of pregnancy loss. As CD146 is detectable as a soluble form in the plasma (sCD146), we investigated sCD146 plasma levels in women with a history of pregnancy loss. We conducted a paired case-control study to compare sCD146 plasma levels in 100 women with unexplained pregnancy losses (2 or more consecutive losses at or before 21 weeks of gestation, or at least one later loss) and in 100 age-matched control women (no pregnancy loss and at least one living child). The sCD146 concentrations were determined at least 2 months after the last obstetrical event. Patients and controls were comparable regarding thrombophilia. Among the patients, 83 women experienced early pregnancy losses (average of 3 losses, mean gestation of 6.6 weeks) and 22 women suffered at least one late pregnancy loss. We found significantly higher sCD146 plasma levels in the 100 patients compared to age matched control women (p < 0.001). The sCD146 plasma levels did not correlate with the number of pregnancy losses nor with the mean gestation time. Alterations in sCD 146 plasma levels could be related to endothelial dysfunction associated to defective endovascular trophoblast invasiveness. Additional studies should explore whether sCD146 assessment could provide diagnostic and prognostic information with a view to screening and thus managing women with unexplained pregnancy loss.