To evaluate the newly implanted and growing embryo, quantitative serum β-hCG or serum progesterone has been used. These tests have been used most often to evaluate women with uterine bleeding in early pregnancy, ectopic pregnancy, luteal phase dysfunction, or a history of habitual abortion. Although serum levels of progesterone may decline before a spontaneous abortion, the clinical usefulness of this test is uncertain.138 Because most spontaneous abortions are not the result of progesterone deficiency, declining progesterone levels often signify dying trophoblasts and a nonviable pregnancy.

With the development of accurate and rapid quantitative measurements of β-hCG in serum, these tests have been used extensively to confirm a normal developing embryo and trophoblast in women treated for various forms of infertility (see Chap. 112). A doubling of the β-hCG levels at ˜48-hour intervals usually signifies a normal viable intrauterine pregnancy,139 whereas low or falling levels are usually associated with an inevitable abortion or an ectopic pregnancy.140 The number of days required for β-hCG levels to normalize following pregnancy and pregnancy complications is seen in Table 108-1.