In this article, we address issues about thrombotic risk and use of antithrombotic prophylaxis during assisted reproductive technologies (ART) and during pregnancies after ART. Many aspects of these complications remain not completely understood and data about incidence, pathogenesis, duration and magnitude of the risk, role of thrombophilias and thromboprophylaxis in determining first events and recurrences are lacking. The role of known or possible risk factors and the efficacy of antithrombotic prophylaxis will be discussed.