Landmarks during the first forty-two days of gestation demonstrated by the beta-subunit of human chorionic gonadotropin and ultrasound.

Prospective pregnancy evaluation through the combined use of a radioimmunoassay (RIA) for the beta-subunit of human chorionic gonadotropin (beta-hCG) and ultrasound during the first 42 days of gestation after ovulation was performed on a population asymptomatic for first-trimester spontaneous abortion. One hundred forty-six ultrasonic observations in 98 pregnancies were made with simultaneous beta-hCG RIA performed in 80 patients. The following landmarks of normal gestational growth were identified: (1) Before 26 days, beta-HCG RIA permits definitive diagnosis of growing trophoblastic tissue, and serial samples allow doubling time computation for prognosis while ultrasound shows a nonspecific increasing decidual response within the uterus; (2) between 26 and 36 days after ovulation, serial beta-hCG samples continue to give doubling time results while ultrasonic demonstration of a gestational sac is normally seen by 28 days after ovulation; (3) the lack of fetal heart motion by 42 days after ovulation or within a gestational sac with a mean diameter of greater than 30 mm was prognostic of abortion; (4) the absence of a gestational sac by 28 days after ovulation or with a beta-hCG RIA greater than 1,000 ng/ml is suggestive of an ectopic pregnancy until proved otherwise.