AbstractThe diagnostic and prognostic value of ultrasound, β‐HCG subunit, and progesterone are evaluated in a prospective study in 169 patients with threatened abortion. Ultrasound diagnosis had just been introduced at the hospital when the study began and clinicians accepted the patients for treatment without receiving the ultrasound, HCG, or progesterone results. With ultrasound, a correct diagnosis of the in utero situation (true positive and true negative) was made at admission in 93% and after 1 week in 99% of the cases; in 1% of the cases intact pregnancies were mistaken for abortions (false positive). For the tests applied, ultrasound had the highest sensitivity in detecting a pathologic pregnancy and also the best predictive value when a pathologic condition was discover