If a girl has weak pelvic floor muscle mass help and tissue harm from childbirth or pelvic medical procedures, a absence of estrogen can even more weaken the pelvic muscles and add to pressure urinary incontinence. Physical alterations resulting from pregnancy, childbirth, and menopause often contribute to stress urinary incontinence. During the 3rd phase of labor, although the infant is becoming born, the vagina undergoes significant variations.