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Inherited thrombophilias are associated with an increased risk of venous thromboembolism (VTE) and the risk is further increased during pregnancy. However, not all pregnancies or all thrombophilias carry the same risk. Deficiencies in coagulation inhibitors and especially in antithrombin are rare but are associated with a higher risk than the most frequent factor V Leiden or prothrombin (factor II) 20210A mutations. Differences may be observed depending on heterozygosity or homozygosity of the defects and on the presence of combined thrombophilias. Although we now have more information on the global risk of thrombosis in thrombophilia, the magnitude of the risk is unknown in women who do or do not have a history of VTE, and in those who are the propositus or family members. Additional risk factors may be taken into account such as age of the mother, cesarean section, obesity, and immobilization during pregnancy. Recommendations of the American College of Chest Physicians (ACCP) concerning prophylaxis during pregnancy published in 2001 are mostly 1C recommendations; they are based on observational studies and subject to changes when more information becomes available. There is now a consensus about prevention in the postpartum period in women with thrombophilia. In contrast, prophylaxis in the antepartum period is often determined on an individual basis. We give some indications of the appropriate prophylaxis on the basis of the ACCP recommendations and personal experience.

We have studied the platelet count and the megathrombocyte index (MI), or percentage of platelets that have a diameter greater than 2.9 μm, in 100 patients with valvular heart disease. The mean platelet count is significantly lower than in controls (p < 0.0005) and the MI is significantly increased (p < 0.01). No difference was observed in these two parameters according to the variety of the valvular heart disease. 45 of the same patients were studied after prosthetic heart valve replacement. Our results show a significant elevation of platelet count and a significant decrease of MI compared with the presurgical values in all groups except in the mitral one in which MI remains increased. This work demonstrates the presence of platelet abnormalities which reveal a compensated thrombo-cytolytic state in patients with valvular heart disease and its partial correction after aortic, but not mitral, valve replacement.

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