Birth related urinary incontinence (UI) is a predictor of UI in older women. Ways to protect the continence mechanism during delivery may diminish a woman's risk of UI later in life. We propose to study the functional anatomy of the pelvic floor as it relates to UI in women who are having their first baby. We hypothesize non-directed, spontaneous pushing is a protective strategy in decreasing the risk of immediate and long term UI. Longitudinal comparisons of pelvic floor characteristics will be taken at 35 week gestation and 6 weeks, 6 months, and 12 months postpartum. Study participants will be seen first at 20 weeks gestation for documentation of baseline levels of pelvic floor function, specifically voluntary and involuntary muscle strength, urinary continence status, and urethral support. They will be randomly assigned into non-directed, spontaneous (experimental) and directed, sustained pushing (control) groups. Alterations that may occur in urethral support before and after birth will be described through non-invasive urethral ultrasound.