The overall pelvic anatomy and orientation of the pelvic organs is similar to the nongravid state (see Chapter 35 Emergency Hysterectomy) with the following exceptions:

• Prior to the 12th week of pregnancy, the uterus is protected by the bony pelvis, but as it grows out of the pelvis, it becomes more susceptible to injury. By 20 weeks, the fundus reaches the umbilicus, and gestational age may be estimated by fundal height. The number of centimeters above the pubic symphysis corresponds to the estimated gestational age in weeks.

• Physiologic changes in blood flow that result in diffuse engorgement of the uterine, ovarian, and salpingeal vasculature. Gravid or postpartum hysterectomies are more difficult and result in higher blood loss than when performed in the nongravid setting. Damage to this vasculature can quickly lead to exanguination.