The goal of this clinical trial is to test the efficacy of the perineal massage in reducing the levator ani muscle (LAM) co-activation. This phenomenon is characterized by the LAM contraction rather than its relaxation during the Valsalva maneuver and it is associated with adverse obstetric outcome. Participants who co-activate will be enrolled and randomized in 2 groups: group A, where women themselves perform the perineal massage during the third trimester of pregnancy and group B, where women undergo the standard care. Researchers will compare these groups to see if the perineal massage is able to reduce LAM co-activation.