We assessed the frequency of abnormal sonographic findings and their significance with respect to outcome in pregnancies resulting from in vitro fertilization (IVF). We retrospectively reviewed first trimester sonograms of 53 consecutive IVF patients who had a positive pregnancy test and first trimester ultrasonography at least 4 weeks after embryo transfer, and we correlated the sonographic findings with pregnancy outcome. For controls, we compared the frequency of sonographic abnormalities in these study patients to that in a group of patients who became pregnant after ovulation induction only. In the 53 IVF patients, the numbers of gestational sacs identified on the initial sonogram were as follows: 34 singletons, 11 twins, two triplets, one quadruplets and one quintuplets; no sac was seen in four patients. In 32 patients, the first sonogram was normal, with a visualized yolk sac, or heartbeat, or both. In 10 patients the gestational sac appeared abnormal but sac contents were normal. In seven patients an abnormality of sac contents was identified, including four with an embryo but no heartbeat and three anembryonic sacs. Overall, 40% of IVF patients had sonographic abnormalities, in comparison to 7% in the control group of patients (P less than 0.05, Fisher's exact test). Of the 32 patients with normal sonograms, 26 (81%) delivered at least one live infant. Of the 10 patients whose gestation sacs appeared abnormal, nine (90%) gave birth to live infants. Of the seven patients with abnormal sac contents, two (29%) delivered at least one live infant. We conclude that abnormal findings are frequently present on the initial sonogram of pregnant patients after IVF.(ABSTRACT TRUNCATED AT 250 WORDS)