A contingent model for cell-free DNA testing to detect fetal aneuploidy after first trimester combined screening

Abstract

A contingent model for cell-free DNA testing to detect fetal aneuploidy after first trimester combined screening Carmen Cotarelo-Péreza,*, Raluca Oancea-Ionescua, Eloy Asenjo-de-la-Fuenteb, Dolores Ortega-de-Herediac, Patricia Soler-Ruizb, Pluvio Coronado-Martínb, María Fenollar-Cortésa a Clinical Genetics Unit, Hospital Universitario Clínico San Carlos, Madrid, Spain b Department of Obstetrics and Gynaecology, Hospital Universitario Clínico San Carlos, Madrid, Spain c Department of Biochemistry, Hospital Universitario Clínico San Carlos, Madrid, Spain A R T I C L E I N F O Article history: Received 3 May 2018 Received in revised form 20 December 2018 Accepted 22 December 2018 Available online 15 January 2019 Keywords: Cell-free fetal DNA test Chromosomal abnormalities Aneuploidy First trimester combined screening Contingent model A B S T R A C T Objective: To assess the results of the first trimester combined test to design a prenatal protocol for the introduction of the cell-free fetal DNA test as a contingent screening model. Method: An observational retrospective study in 12,327 singleton pregnancies to analyze the results of the combined first trimester screening, the nuchal translucency 97.5 percentile, their cytogenetic results and birth outcomes. Results: A total of 533 (4.3%) pregnant women had a risk in combined first trimester screening above 1/ 300. In this group, sixty nine had an unbalanced karyotype. The abnormal/normal karyotype ratio was 1/ 28 in pregnant women with intermediate risk (1/51-1/300) for trisomy 21 and trisomy 18, 1/58 with intermediate risk just for trisomy 21 and 1/37 with intermediate risk just for trisomy 18. A 19.8% of the unbalanced karyotypes had chromosomal abnormalities other than trisomies 21, 18 and 13. Two false negatives cases at first trimester combined screening presented a nuchal translucency

p97.5th. Conclusion: We propose the introduction of the cell-free fetal DNA test when the risk of first trimester combined screening is intermediate (1/51–1/300) and when nuchal translucency is

p97.5th with a low risk in the combined screening. This policy would allow us to continue to detect uncommon chromosomal abnormalities.