FIGURE 36-3 Risk of deep-vein thrombosis or pulmonary embolism following childbirth. (Data from Kamel H, Navi S, Sriram N, et al: Risk of a Thrombotic Event after the 6-week postpartum period. N Engl J Med 370:1307,o2014.)
When the amount of blood attained by normal pregnancy hypervolemia is lost as postpartum hemorrhage, the woman almost immediately regains her nonpregnant blood volume (Chap. 41, p. 756). If less has been lost at delivery, blood volume generally nearly returns to its nonpregnant level by 1 week after delivery. Cardiac output usually remains elevated for 24 to 48 hours postpartum and declines to nonpregnant values by 10 days (Robson, 1987). Heart rate changes follow this pattern, and blood pressure similarly returns to nonpregnant values (Fig. 36-4). Correspondingly, systemic vascular resistance remains in the lower range characteristic of pregnancy for 2 days postpartum and then begins to steadily increase to normal nonpregnant values (Hibbard, 2014). Despite this, Morris and coworkers (2015) found that reduced arterial stifness persists following pregnancy. They suggest a signiicant favorable
FIGURE 36-4 During the early puerperium, blood pressure normally rises toward nonpregnant values. MAP = mean arterial pressure.
efect of pregnancy on maternal cardiovascular remodeling, which may represent a mechanism by which preeclampsia risk is reduced in subsequent pregnancies.
Normal pregnancy is associated with an appreciable increase in extracellular sodium and water retention, and postpartum diuresis is a physiological reversal of this process. Chesley and coworkers (1959) demonstrated a decrease in sodium space of approximately 2 L during the first week postpartum. his also corresponds with loss of residual pregnancy hypervolemia. In preeclampsia, pathological retention of luid antepartum and its diuresis postpartum may be prodigious (Chap. 40, p. 744).
Postpartum diuresis results in relatively rapid weight loss of 2 to 3 kg, which is additive to the 5 to 6 kg incurred by delivery and normal blood loss. Weight loss from pregnancy itself is likely to be maximal by the end of the second week postpartum. It follows that any residual increased weight compared with prepregnancy values probably represents fat stores that will persist. According to Schauberger and associates (1992), women approach their self-reported prepregnancy weight 6 months after delivery but still retain an average surplus of 1.4 kg (3 Ib).
Each mature mammary gland or breast is composed of 15 to 25 lobes. hey are arranged radially and are separated from one another by varying amounts of fat. Each lobe consists of several lobules, which in turn are composed of numerous alveoli. Each alveolus is provided with a small duct that joins others to form a single larger duct for each lobe as shown in Figure 36-5. These lacterous ducts open separately on the nipple, where they may be distinguished as minute but distinct orifices. he alveolar secretory epithelium synthesizes the various milk constituents.