Clinical significance of first-trimester chorionic bumps: a matched case-control study

To determine the clinical significance of a chorionic bump diagnosed by ultrasound in women attending an early pregnancy unit in a teaching hospital.

This was a retrospective case-control study over an 8-year period (2003-2010). Cases of chorionic bump were identified by searching our early pregnancy database and were matched to controls in a ratio of 1:3. The primary outcome measure was miscarriage vs ongoing pregnancy. Secondary outcomes were gestational age at delivery and the presence or absence of fetal abnormality.

A total of 37 798 pregnancies were examined over the study period and 57 pregnancies with a chorionic bump were identified, giving an estimated prevalence of 1.5 per 1000 pregnancies (0.15%; 95% CI, 0.01-0.73%). Of the 52 women with follow-up data, 20 (38.5%; 95% CI, 26.4-52.1%) miscarried vs 31/151 (20.5%; 95% CI, 14.8-27.7%) in the control group (P = 0.01). There were four second-trimester miscarriages in the study group and none in the controls (P < 0.01). Out of 52 pregnancies in the study group there were 32 live births (62%; 95% CI, 47.9-73.6%) vs 118/151 (78%; 95% CI, 70.9-84.0%) in the control group (P = 0.02). There were no differences in preterm delivery rates or fetal anomalies. No significant relationship was found between size of the bump or location in relation to the umbilical cord insertion and risk of miscarriage.

Women presenting to early pregnancy units with a chorionic bump discovered at first-trimester ultrasound examination had approximately double the risk of miscarriage compared with matched controls, the difference being due to a greater number of miscarriages during the second trimester of pregnancy.