[CLINICAL IMPLEMENTATION OF CELL-FREE DNA ANALYSIS IN MATERNAL BLOOD IN SCREENING FOR ANEUPLOIDIES IN SINGLETON PREGNANCIES].

Objective: Clinical implementation of cell free(cf) DNA testing in maternal blood for aneuploidies in singleton pregnancies.

Methods: This is a retrospective study conducted in two centers for fetal medicine in Sofia, Bulgaria, between October 2013 and August 2015. We examined the clinical implementation of cf DNA testing in the routine practice for trisomies 21, 18 and13 after the performance of the first trimester combined test, second trimester biochemical test and/or the combination between first and second trimester integrated test.

Results: Cell-free DNA testing was performed in 170 singleton pregnancies with a median maternal age of 35 (range 22-46) years. The primary risk assessment for aneuploidies was derived from 95 cases after the first trimester combined screening test, 39 cases after the second trimester biochemical screening test, 16 cases after the integrated screening test and 20 cases there were no screening test performed. The results from the first line screening test were : 8 pregnancies with risk for trisomy 21 > 1: 100; 23 pregnancies with risk for trisomy 21 from 1:100 to 1: 300; 43 pregnancies with risk for trisomy 21 from 1:300 to 1:1000 and 76 pregnancies with risk for trisomy 21 < 1: 1000. No pregnancies with high risk for T13/T18 were identified. The analysis of cf DNA in the maternal blood reported 3 cases with T21 and no cases with T18 or T13. There was only one case of T21 in the group with risk >1:100 identified by the cf DNA analysis which was also identified by the first trimester combined screening test. The positive results were confirmed with invasive testing: CVS in the first trimester (one case) and Amniocentesis in the second trimester (two cases).

Conclusion: Clinical implementation of cell-free DNA analysis in the contingent policy for screening could improve the detection rate for T21 and could reduce the rate of invasive procedures.