After initial admission of the patients for Cesarean Section, Vaginal Delivery or any other antepartum hospitalization, patients undergo extensive counseling regarding various aspects of the Duplex Ultrasonography procedure and the purpose of the study for screening of the venous thrombosis in asymptomatic patients. Patients electing to proceed will have written informed consent obtained and their baseline demographic and medical characteristics recorded. 48-72 hours after Cesarean Section, 24-48 hours after vaginal delivery and 48 to 72 hours after antepartum hospitalization, participants also undergo a bilateral lower extremity Venous Ultrasonographic examination which is the standard diagnostic procedure for detecting the VTE of the lower limbs. The latter group will be re-scanned 14-21 days and, when feasible, 45 days after admission.