The chorionic bump: a first-trimester pregnancy sonographic finding associated with a guarded prognosis.

OBJECTIVE: We describe a series of patients with a previously unreported sonographic finding, the chorionic "bump," which is an irregular, convex bulge from the choriodecidual surface into the first-trimester gestational sac. The pregnancy outcome is investigated in this series of patients and compared with the general population and infertility first-trimester control groups. METHODS: We prospectively noted a cohort of 15 cases with the chorionic bump on first-trimester sonograms (in a total of 2178 patients) performed over 3 years at our institution (prevalence, 0.7%). We then compared pregnancy outcomes against 2 pregnant control groups (15 general, noninfertility patients and 15 infertility patients) who were maternal age and gestational age matched to our patient group. RESULTS: The difference in outcomes between the patients with bumps and the healthy control subjects was statistically significant (7 live births versus 13 live births; P < .03), but the difference in outcomes between the patients with bumps and infertility control subjects was not statistically significant (7 live births versus 11 live births; P = .1). Bump size was not correlated with pregnancy outcome. In most patients with serial sonograms, the bump showed evolutionary changes typical for hematoma. CONCLUSIONS: The finding of a chorionic bump on the first-trimester sonogram is associated with a guarded prognosis for the early pregnancy (live birth rate <50%); it probably represents a small hematoma that bulges into the gestational sac, and, in our series, most patients had a history of infertility treatments.