a. Blood Volume.

Initially, there is a 15 to 30 percent increase in circulating blood volume the first 20 days of postpartum.

This results from the elimination of placental circulation and an increase in venous return.

The increase is responsible for profound diuresis in early postpartum and a fall in hematocrit. This is why early postpartum time is the greatest risk for heart failure in patients with cardiac disease or limited cardiac reserve.

b. Hematocrit.

The hematocrit drops because of blood loss during actual delivery. It usually rises by the third to seventh postpartum day unless substantial blood loss has occurred. Normal blood loss is about 250cc for vaginal delivery. This varies considerably. Blood loss must be greater than 500cc to be considered hemorrhage.