PROS1 and Rare hereditary thrombophilia: Only “conception” or prepregnancy prospective cohorts would permit prospective examination of this issue; (2) we had insufficient data and hence power to detect important associations between PGM and pregnancy loss as well as FVL or PGM and placental abruption; (3) there are insufficient prospective cohort studies examining the less common and more potent thrombophilias such as antithrombin, protein C, and protein S deficiencies to elucidate associations between these thrombophilias and placenta-mediated pregnancy complications.