An in-vivo measurement procedure is presented to characterize the mechanical behavior of human uterine cervix during pregnancy. Based on the aspiration method, a new instrument was developed to provide an inherently safe and easy-to-use mechanical testing technique. Initial measurements were performed on non-pregnant women to develop an appropriate measurement protocol. An inverse analysis was carried out to determine representative model equations for cervical tissue. This model was used in a FE based parametric study focusing on the uncertainties related to the experiment. On this basis, a novel procedure was established which enabled for the first time to conduct mechanical measurements on 50 pregnant women in over 600 applications during gestation. An inverse analysis of the average tissue response at each trimester was performed to determine representative model equations for the cervix in the course of pregnancy.