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First Trimester Contingent Screening for Aneuploidies with Cell-Free Fetal DNA in Singleton Pregnancies - a Swiss
Alice Proto1, Fabienne Trottmann1, Sophie Schneider1
1Department of Obstetrics and Gynaecology, University Hospital of Bern, University of Bern, Inselspital, Bern, Switzerland.
Introduction:
Switzerland was amongst the first countries to offer cell-free fetal DNA (cffDNA) testing covered by the health insurance to pregnant women with a risk ≥ 1:1000 for trisomies at first trimester combined screening (FTCS). The aim of this study is to evaluate the implementation of this contingent model in a single tertiary referral centre and its effect on gestational age at diagnosing trisomy 21.
Materials And Methods:
Between July 2015 and December 2020 all singleton pregnancies at 11-14 weeks of gestation without major fetal malformation were included and stratified according to their risk at FTCS. Statistical analysis was performed by GraphPad Version 9.1 for Windows.
Results:
4424 pregnancies were included. Of 166 (3.8%) pregnancies with a NT ≥ 3.5 mm and/or a risk ≥ 1:10 at FCTS, 130 (78.3%) opted for direct invasive testing. 803 (18.2%) pregnancies had an intermediate risk, 692 (86.2%) of them opted for cffDNA first. 3455 (78.1%) pregnancies had a risk < 1:1000. 63 fetuses were diagnosed with trisomy 21, 47 (74.6%) directly by invasive procedures after FTCS, 16 (25.4%) by cffDNA first.
Conclusions:
Most women choose cffDNA or invasive testing as second tier according to national guidelines. Despite the delay associated with cffDNA testing after FCTS, 75% of all trisomy 21 are still diagnosed in the first trimester with this contingent screening model.
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