[THE RISK FOR CLINICALLY SIGNIFICANT COPY NUMBER VARIANTS IN PREGNANCIES WITH TWO SOFT MARKERS]

Soft sonographic markers, such as an intracardiac echogenic focus, are demonstrated in one out of 150 live births and are associated with a slightly increased risk of trisomy 21 and 18. In the case of an isolated soft marker, the recommendation to perform invasive tests such as amniocentesis or placental cyst testing depends to a large extent on the results of biochemical first and second trimester maternal serum screening. In the case of two soft markers, the women are referred to genetic counseling, and invasive testing is funded by the Ministry of Health.

To estimate the risk for clinically significant copy number variants (CNVs) in pregnancies with two soft markers.

This retrospective cohort study included all prenatal microarray tests performed during 2013-2021, due to demonstration of two soft markers (namely: echogenic intracardiac foci, choroid plexus cyst, single umbilical artery and mild pyelectasis). The rates of clinically significant (pathogenic and likely pathogenic) microarray findings were compared to a previously published cohort of 7235 pregnancies with normal ultrasound, in which 87 (1.2%) abnormal CNVs were noted.

Of the 150 pregnancies with two soft markers, two (1.3%) clinically significant CNVs were found. The rate of abnormal microarray findings did not differ from baseline risk in pregnancies with normal ultrasound - relative risk of 1.11 (95% confidence interval 0.28-4.40).

The risk for abnormal microarray findings in pregnancies with two soft markers was not significantly increased in comparison to control group of pregnancies with normal sonography.

These results undermine the current national policy of genetic counseling and Ministry of Health-funded invasive testing in pregnancies with a combination of two soft markers. These findings are important for additional countries with similar management, and may facilitate the genetic counseling and informed decision-making in such cases.