The purpose of this study is to understand the effect of the pregnancy on the muscles in the pelvis. The purpose of this study is to evaluate the pelvic muscle changes related to pregnancy; to assess if the ability to squeeze and relax these muscles has any effect on delivery mode and if there are any injuries to the pelvic muscles.

Healthy women who are pregnant with their first child will be included in the study. Information about their general health will be gathered. These women will be screened for pelvic disorders at the start and end of study. Three-dimensional ultrasound will be performed three times: 12-24 weeks, 34-39 weeks and 4-6 weeks after delivery. Fetal measurements will be included in the third trimester ultrasound for prediction of estimated birth weight. The relationship of the predicted fetal weight and the likelihood of having a successful vaginal delivery will be studied. Images will be analyzed for pelvic muscles function and injuries. Information regarding the length of labor, types of delivery and vaginal tears will be gathered. The information obtained will be analyzed to look for the strength of correlation of variables to the outcomes.

Inclusion Criteria:

• Primiparous or should not have given birth to a fetus older than 12 weeks.
• Singleton pregnancy.
• Age more than or equal to 18 years.
• Basal mass index between 18 - 40 kg/m2.
• Must plan to deliver at Strong Memorial Hospital at the University of Rochester Medical Center.

Exclusion Criteria:

• Basal mass index more than 40 kg/m2.
• Presence of current or prior history of cervical incompetence.
• Presence of diabetes mellitus (type I or type II).
• Presence of connective-tissue disorders such as Systemic lupus erythematosus, Rheumatoid Arthritis, or Sjogren's disease.
• Presence of neuromuscular disorders such as myasthenia gravis and neuropathies.

Prenatal visits