gynecology and obstetrics
Physiology of Pregnancy
Symptoms and Signs of Pregnancy
 (beta-hCG) by syncytial cells of the placenta, beginning 10 days after fertilization (see Conception and Prenatal Development ). The corpus luteum in the ovary, stimulated by beta-hCG, continues secreting large amounts of Women usually begin to feel fetal movement between 16 and 20 weeks. During late pregnancy, lower-extremity edema and varicose veins are common; the main cause is compression of the inferior vena cava by the enlarged uterus. Pelvic examination findings include a softer cervix and an irregularly softened, enlarged uterus. The cervix usually becomes bluish to purple, probably because blood supply to the uterus is increased. Around 12 weeks gestation, the uterus extends above the true pelvis into the abdomen; at 20 weeks, it reaches the umbilicus; and by 36 weeks, the upper pole almost reaches the xiphoid process. 