First‐trimester chorionic bump‐‐Association with fetal aneuploidy in a high‐risk population

ABSTRACT Purpose To determine the relationship between the first‐trimester chorionic bump and fetal aneuploidy. Methods This retrospective cohort study included all singleton pregnancies with chromosomal analysis and sonographic examination performed between 5 0/7 and 13 6/7 weeks from January 1, 2010 through August 15, 2015. Interobserver and intraobserver agreement for identifying a chorionic bump was evaluated by the Kappa statistic. Pregnancies with and without a chorionic bump were compared regarding patient characteristics and fetal karyotypes. Results Six hundred ninety subjects were included, 16 (2.3%) having a bump. The kappa coefficients for interobserver agreement were 0.88 (95% confidence interval [CI]: 0.71–1.00) and 0.94 (95% CI: 0.82–1.00); those for intraobserver agreement were 0.81 (95% CI: 0.61–1.00) and perfect agreement. One hundred seventeen fetuses (16.9%) were aneuploid, of which five (4.3%) had a bump. The odds of aneuploidy in the presence of a chorionic bump were higher than those in the absence of a chorionic bump, although this difference was not statistically significant (odds ratio [OR] 2.3, 95% CI: 0.8–6.7). In subgroup analyses, odds of aneuploidy were four times higher in the bump group than in the no bump group among those with a sonographically isolated bump (OR 4.5, 95% CI: 1.5–13.5) and 15 times higher among those with an isolated bump and increased first‐trimester aneuploidy risk (OR 15.0, 95% CI 2.4–93.3). Conclusions Agreement in identifying chorionic bumps is near‐perfect. A sonographically nonisolated chorionic bump is not associated with significant additional aneuploidy risk, whereas a sonographically isolated chorionic bump confers a significantly increased likelihood of aneuploidy in high‐risk fetuses. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:3–7, 2017