Puerperium is defined as the time from the delivery of the placenta through the first few weeks after the delivery. This period is usually considered to be 6 weeks in duration. By 6 weeks after delivery, most of the changes of pregnancy, labor, and delivery have resolved and the body has reverted to the nonpregnant state.
An overview of the relevant anatomy and physiology in the postpartum period follows.
The pregnant term uterus (not including baby, placenta, fluids, etc) weighs approximately 1000 g. In the 6 weeks following delivery, the uterus recedes to a weight of 50-100 g.
Immediately postpartum, the uterine fundus is palpable at or near the level of the maternal umbilicus. Thereafter, most of the reduction in size and weight occurs in the first 2 weeks, at which time the uterus has shrunk enough to return to the true pelvis. Over the next several weeks, the uterus slowly returns to its nonpregnant state, although the overall uterine size remains larger than prior to gestation.
The endometrial lining rapidly regenerates, so that by the seventh day endometrial glands are already evident. By the 16th day, the endometrium is restored throughout the uterus, except at the placental site.
The placental site undergoes a series of changes in the postpartum period. Immediately after delivery, the contractions of the arterial smooth muscle and compression of the vessels by contraction of the myometrium (“physiologic ligatures”) result in hemostasis. The size of the placental bed decreases by half, and the changes in the placental bed result in the quantity and quality of the lochia that is experienced.
Immediately after delivery, a large amount of red blood flows from the uterus until the contraction phase occurs. Thereafter, the volume of vaginal discharge (lochia) rapidly decreases. The duration of this discharge, known as lochia rubra, is variable. The red discharge progressively changes to brownish red, with a more watery consistency (lochia serosa). Over a period of weeks, the discharge continues to decrease in amount and color and eventually changes to yellow (lochia alba).
The period of time the lochia can last varies, although it averages approximately 5 weeks.
The amount of flow and color of the lochia can vary considerably. Fifteen percent of women have continue to have lochia 6 weeks or more postpartum. Often, women experience an increase in the amount of bleeding at 7-14 days secondary to the sloughing of the eschar on the placental site. This is the classic time for delayed postpartum hemorrhages to occur.
The cervix also begins to rapidly revert to a nonpregnant state, but it never returns to the nulliparous state. By the end of the first week, the external os closes such that a finger cannot be easily introduced.
The vagina also regresses but it does not completely return to its prepregnant size. Resolution of the increased vascularity and edema occurs by 3 weeks, and the rugae of the vagina begin to reappear in women who are not breastfeeding. At this time, the vaginal epithelium appears atrophic on smear. This is restored by weeks 6-10; however, it is further delayed in breastfeeding mothers because of persistently decreased estrogen levels.
The perineum has been stretched and traumatized, and sometimes torn or cut, during the process of labor and delivery. The swollen and engorged vulva rapidly resolves within 1-2 weeks. Most of the muscle tone is regained by 6 weeks, with more improvement over the following few months. The muscle tone may or may not return to normal, depending on the extent of injury to muscle, nerve, and connecting tissues.
The abdominal wall remains soft and poorly toned for many weeks. The return to a prepregnant state depends greatly on maternal exercise.
The resumption of normal function by the ovaries is highly variable and is greatly influenced by breastfeeding the infant. The woman who breastfeeds her infant has a longer period of amenorrhea and anovulation than the mother who chooses to use formula. The mother who does not breastfeed may ovulate as early as 27 days after delivery. Most women have a menstrual period by 12 weeks; the mean time to first menses is 7-9 weeks.
In the breastfeeding woman, the resumption of menses is highly variable and depends on a number of factors, including how much and how often the baby is fed and whether the baby’s food is supplemented with formula. The delay in the return to normal ovarian function in the lactating mother is caused by the suppression of ovulation due to the elevation in prolactin. Half to three fourths of women who breastfeed return to periods within 36 weeks of delivery.
The changes to the breasts that prepare the body for breastfeeding occur throughout pregnancy. Lactogenesis, which is the development of the ability to secrete milk, occurs as early as 16 weeks gestation. The placenta supplies high levels of circulating progesterone which activates mature alveolar cells in the breast to secrete small amounts of milk. After delivery of the placenta, there is a rapid decline in progesterone which triggers the onset of milk production and subsequent swelling, or engorgement, of breasts in the postpartum period. The colostrum is the liquid that is initially released by the breasts during the first 2-4 days after delivery. High in protein content and antibody rich, this liquid is protective for the newborn. The colostrum, which the baby receives in the first few days postpartum, is already present in the breasts, and suckling by the newborn triggers its release. The process, which begins as an endocrine process, switches to an autocrine process; the removal of milk from the breast stimulates more milk production. Over the first 7 days, the milk matures and contains all necessary nutrients in the neonatal period. The milk continues to change throughout the period of breastfeeding to meet the changing nutritional demands of the baby.
Lactation is the process of continued secretion of copious milk. Lactation requires regular removal of milk (ie breast emptying) which triggers prolactin release from the anterior pituitary gland. It also requires nipple stimulation (ie suckling) which triggers oxytocin from the posterior pituitary gland. Oxytocin release after tactile stimulation of the nipple-areolar complex causes myoepithelial cells of the breasts to contract, which forces milk into the alveolar lumens and then into the ducts, prior to moving out through the nipple. If the mother is not breastfeeding, the absence of milk removal leads to elevated intramammary pressure as the milk accumulates within the alveolar lumen. Alveolar distention restricts blood flow to the alveoli and interferes with milk production. Additionally, the increase in pressure triggers an inhibitor of lactation (FIL) which decreases prolactin levels and triggers mammary involution within 2-3 weeks.