NORMAL ANATOMIC AND PHYSIOLOGIC CHANGES
The puerperium is the period that begins after the delivery of the placenta and lasts until the reproductive organs have returned to approximately their prepregnant condition. The puerperium is usually considered to last 6 weeks.
Postpartum shivering is observed in 25 to 50 percent of women after normal delivery. The pathogenesis of postpartum chills is not clear. No treatment is necessary other than supportive care. When shivering is anesthesia related, it can be treated pharmacologically.
After the delivery of the placenta and membranes, contractions reduce the size of the uterus so that it can be felt as a hard, globular mass lying just below the umbilicus. Contraction of interlacing myometrial muscle bundles constricts the intramyometrial vessels, impeding blood flow and preventing postpartum hemorrhage. Moreover, large vessels at the placental site thrombose, a secondary hemostatic mechanism for preventing blood loss at this site.
The uterus weighs 1000 to 1200 g immediately after delivery. It rapidly falls to 500 g by 7 days, disappears into the pelvis by 2 weeks, and is back to its nonpregnant weight of 50 to 70 g by 6 weeks. This reduction is the result mainly of a decrease in the size of the myometrial cells rather than of their number.
Involution of the placental site also takes up to 6 weeks. Immediately after delivery, the placental site is elevated, irregular, and friable and is composed of thrombosed vascular sinusoids. These undergo gradual hyalinization. Most of the decidua basalis is shed over a period of weeks and is replaced by regenerating endometrium. Failure of normal involution of the placental site may lead to late postpartum hemorrhage.
The basal portion of the decidua remains after delivery of the placenta. The decidua divides in two layers: the superficial layer and the deep layer. The deep layer, which contains some endometrial glands, regenerates new endometrium. Restoration of the endometrial cavity is rapid and is complete in 16 to 21 days. The superficial layer of decidua surrounding the placental site becomes necrotic and is sloughed off during the first 5 to 6 days. This postpartum vaginal discharge, made up of a mixture of blood and necrotic decidua, is called “lochia.” It is red for 2 to 3 days (lochia rubra), becomes paler as the bleeding is reduced (lochia serosa), and by 7 days is yellowish-white (lochia alba). The total volume of postpartum lochial secretion is 200 to 500 mL and lasts from 3 to 6 weeks.
Regeneration of the Endometrium
The deeper part of the decidua that contains some endometrial glands remains intact and is a source of a new lining of the uterine cavity. Restoration of the endometrium is rapid; by the seventh day, it ...