A contingent model for cell-free DNA testing to detect fetal aneuploidy after first trimester combined screening.
Eur J Obstet Gynecol Reprod Biol X 2019;
1:100002. [PMID:
31396589 PMCID:
PMC6683975 DOI:
10.1016/j.eurox.2019.100002]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 12/20/2018] [Accepted: 12/22/2018] [Indexed: 12/02/2022] Open
Abstract
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.
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