Objectives: To evaluate the association between obstetrical complications in pregnancy and thrombophilic factors. Study Design: 75 pregnant women with obstetrical complications and 66 controls with live births without obstetrical complications were tested for thrombophilia. All subjects were negative for thromboembolic disease. Results: The obstetrical complications in the study group were unexplained oligohydramnios = 16 (21%), IUGR = 17 (23%), preeclampsia < 32 weeks = 15 (20%), recurrent abortions = 42 (56%), fetal demise= 14 (19%), abruption= 8 (11%). Comparing women with obstetrical complications versus controls, factor V Leiden mutation was present in 7 (10%) versus 1 (2%) P =.064, odds ratio ( OR)= 7, 95%, CI= 0.8-58.5, antiphospholipid antibody syndrome in 14 ( 19%) versus 2 (3%) P=. 003, OR = 7, 95% CI= 1.7 - 35, high lipoprotein A levels 13 ( 30%) versus 6 (10%) P =.019, OR= 3.8, 95% CI= 1.3-11. In the study group, there was a case each of prothrombin gene mutation, elevated homocysteine level, antithrombin III, protein S&C deficiencies. Major thrombophilia diagnosis was present in 24 (32%) versus 3 (5%) of controls p=.001, OR= 9.8. No association was found with the methylenetetrahydrofolate reductase gene mutation. In 22 women who subsequently became pregnant, prophylactic anticoagulant therapy compared to pretreatment control pregnancies showed 22 versus 11 live births P=. 001, 95% CI= 0.3-0.7 and obstetrical complications of 2 (9%) versus 22 (100%) P =.001, OR = 11, 95% CI = 2.9-41.2. Conclusion: An association is suggested between non-thromboembolic pregnancy complications and hypercoagulable disorders. Prophylactic anticoagulant therapy may be associated with improved pregnancy outcome.