The purpose of this study is to see if fetal head circumference can be used as a predictor for who will experience a sphincter laceration while delivering.

Even though much work has been invested in trying to identify risk factors that can predict which population will suffer from sphincter tears and other pelvic floor trauma, the epidemiology is still poorly understood. Factors that have been implicated to include operative vaginal delivery, birth weight, and primaparity. Up to this point little focus has been placed on antenatal factors that would help predict and prevent sphincter disruptions. At the time of birth the infant's head is the largest part of the body. Thus, head circumference of the infant may be able to predict which subjects is more likely to suffer from sphincter disruption. Thus, this study aims to determine whether or not fetal head circumference measured antenatally is predictive of pelvic floor trauma.

Inclusion Criteria:

• Primiparous subjects at least 18 years of age
• Gestational age greater than or equal to 36 weeks and upto 42 weeks gestation
• Subjects must have give written informed consent to participate in this study
• Subjects must be planning to deliver at UCI

Exclusion Criteria:

• Subjects less than 18 years of age
• Subjects with a previous delivery
• Subjects with previous colorectal surgery or hemorrhoidal surgery
• Subjects with a history of irritable bowel syndrome, ulcerative colitis, or Crohn's disease
• Subjects with a history of colon or rectal cancer
• Gestational age less than 36 weeks
• Cesarean section

Women in 36 weeks and upto 42 weeks of pregnancy