Progressive lordosis is a characteristic feature of normal pregnancy. Compensating for the anterior position of the enlarging uterus, lordosis shifts the center of gravity back over the lower extremities. The sacroiliac, sacrococcygeal, and pubic joints have increased mobility during pregnancy. However, as discussed earlier (p. 52), increased joint laxity and associated discomfort during pregnancy do not correlate with increased maternal serum levels of estradiol, progesterone, or relaxin (Aldabe, 2012; Marnach, 2003; V0llestad, 2012). Most relaxation takes place in the first half of pregnancy. It may contribute to maternal posture alterations and in turn create lower back discomfort. s discussed in Chapter 36 (p. 661), although some symphyseal separation likely accompanies many deliveries, those greater than 1 cm may cause significant pain (Shnaekel, 2015).
Aching, numbness, and weakness also occasionally are experienced in the upper extremities. his may result from the marked lordosis and associated anterior neck flexion and shoulder girdle slumping, which produce traction on the ulnar and median nerves (Crisp, 1964). he latter may give rise to symptoms mistaken for the carpal tunnel syndrome (Chap. 60, p. 1167). Joint strengthening begins immediately following delivery and is usually complete within 3 to 5 months. Pelvic dimensions measured by MR imaging up to 3 months after delivery are not significantly diferent from prep regnancy measurements (Huerta-Enochian, 2006).
Central nervous system changes are relatively few and mostly subtle. Women often report problems with attention, concentration, and memory throughout pregnancy and the early puerperium. Systematic studies of memory in pregnancy, however, are limited and often anecdotal. Keenan and associates (1998) longitudinally investigated memory in pregnant women and a matched control group. hey found pregnancy-related memory decline that was limited to the third trimester. his decline was not attributable to depression, anxiety, sleep deprivation, or other physical changes associated with pregnancy. It was transient and quickly resolved following delivery. Others have found poorer verbal recall and processing speed and worse spatial recognition memory in pregnancy (Farrar, 2014; Henry, 2012).
Zeeman and coworkers (2003) used MR imaging to measure cerebral blood low across pregnancy. They found that mean blood flow in the middle and posterior cerebral arteries declined progressively from 147 and 56 mLimin when nonpregnant to 118 and 44 mLlmin late in pregnancy, respectively. Mechanisms and signiicance of the decline are unknown. Pregnancy does notiafect cerebrovascular autoregulation (Bergersen, 2006; Cipolla, 2014).
Intraocular pressure drops during pregnancy and is attributed partly to greater vitreous outlow. Corneal sensitivity is decreased, and the greatest changes are late in gestation. Most pregnant women demonstrate a measurable but slight increase in corneal thickness, thought to be due to edema. Consequently, they may have diiculty with previously comfortable contact lenses. Brownish-red opacities on the posterior surface of the cornea-Krukenberg spindles-are observed with a higher than expected frequency during pregnancy. Hormonal efects similar to those observed for skin lesions are believed to cause this increased pigmentation. Other than transient loss of accommodation reported with both pregnancy and lactation, visual function is unafected by pregnancy. These changes during pregnancy and pathological eye aberrations were reviewed by Grant and Chung (2013).