Early intrauterine gestational sac recognition by ultrasound is useful for discriminating between intrauterine and tubal pregnancies. Transvaginal ultrasound offers improved resolution in the imaging of the uterus and adnexa. Seventy-four women with normal intrauterine pregnancies, 18 women with spontaneous abortions, and 34 women with tubal pregnancies were evaluated by transvaginal ultrasound and serial hCG determinations. Intrauterine pregnancies were followed within the first 50 days of gestation. In women with a normal uterus and singleton pregnancy, sacs were consistently recognized in association with an hCG level greater than 2004 mIU/mL (First International Reference Preparation). Two- to three-millimeter sacs were recognized in association with an hCG level of 2032 +/- 1253 on cycle day 36.1 +/- 2.0. When sacs were less than 5 mm in mean diameter, 33% exhibited a prominent echogenic rim, 38% exhibited a partial echogenic rim, and 29% exhibited no echogenic rim. Fetal cardiac activity was recognized in association with an hCG level of 27,284 +/- 11,479 on cycle day 45.0 +/- 2.9. The hCG doubling time was 1.46 +/- 1.0 days. Apparent loss of multiple gestational sacs was observed in five normal pregnancies. Apparent bleeding in the intrauterine cavity was observed in eight patients and associated with a 38% abortion rate. One false-positive sac was observed among 34 tubal pregnancies (3%). The extrauterine sonographic finding of a solid adnexal mass or cul-de-sac fluid was specific but not sensitive for the diagnosis of tubal pregnancy. The hCG doubling time in tubal pregnancies was 7.69 +/- 9.8 days. Transvaginal ultrasound and serial hCG determinations are useful for the early recognition of tubal pregnancy.
(C) 1990 The American College of Obstetricians and Gynecologists