Chorionic bump at 11 to 13 weeks' gestation: Prevalence and clinical significance

To gather additional data on pregnancy outcome when a chorionic bump is detected at the time of the 11- to 13-week scan.

The presence of a chorionic bump was prospectively recorded in a database of women presenting for their first-trimester sonographic screening. Clinically relevant information was obtained by reviewing ultrasound reports and medical records or contacting the referring obstetrician or the parents themselves.

During a 4.5-year study period from June 2014 to December 2018, a chorionic bump was identified in 23 out of 3375 pregnancies, for a prevalence of 1/147 or 0.7%. All women were asymptomatic at the time of evaluation. The chorionic bump was single in 21 (91%) cases, located in the central part of the placenta in 17 (74%) cases, and the median largest diameter was 20 mm (range, 10-43). Although the placenta was low-lying in 14 (61%) cases, all but one patient had a normally located placenta at the midtrimester anatomy scan. With the exception of one pregnancy complicated with trisomy 21, the outcome was universally good.

Our experience suggests that a chorionic bump detected during the 11- to 13-week scan is usually a transient, is incidental finding, and probably has no clinical significance.