Unexplained first trimester recurrent pregnancy loss and low venous reserves

More than half of recurrent pregnancy loss (RPL) remains unexplained. We hypothesized that women with a history of unexplained RPL (URPL) have low venous reserve. Casecontrol study in 12 women with a history of URPL, 11 healthy nulliparous controls and 12 primiparous controls with a history of uncomplicated pregnancy. To quantify venous reserve, we measured plasma volume (PV, ml/m(2)) and venous compliance in forearm and calf (VCarm, VCcalf, (ml/dl)/mmHg) during the follicular phase of the menstrual cycle. Mean arterial blood pressure (mmHg) was measured by oscillometry. Arterial demand was evaluated by cardiac index (CI, (l/min)/m(2)). Baseline characteristics were comparable between groups. All groups had similar CI. Women with a history of RPL had 14 and 9 lower mean PV compared with nulliparous and primiparous controls (P 0.01 and P 0.04, respectively). In women with URPL, the mean VCarm was 25 and 32 lower compared with nulliparous and primiparous controls (P 0.04 and P 0.01, respectively), while the mean VCcalf was 29 and 22 lower compared with the two control groups (P 0.01 and P 0.03, respectively). Women with URPL have lower venous reserves when compared with controls at comparable arterial demand. Interventions that increase venous reserve may improve pregnancy outcome.