Performance of cell-free DNA testing for common fetal trisomies in triplet pregnancies

ObjectiveIn singleton pregnancies, the use of cell-free DNA (cfDNA) analysis as a screening test for common fetal trisomies has spread worldwide though we still lack sufficient data for its use in triplet pregnancies. The objective of this study is to assess the performance of cfDNA testing in detecting fetal aneuploidies in triplet pregnancies as a first-tier test.MethodWe performed a retrospective cohort study including data from pregnant women with a triplet pregnancy who underwent cfDNA testing between May 1, 2017, and January 15, 2020. cfDNA was obtained by massive parallel sequencing (VeriSeq NIPT solution; Illumina (R)). The objectives of the study were to assess the diagnostic performance of cfDNA testing for trisomy 21 (T21) (primary outcome), trisomy 18 (T18) and 13 (secondary outcomes).ResultsDuring the study period, cfDNA testing was performed in 255 women with triplet pregnancy, of which 165 (64.7%) had a neonatal outcome available. Three tests were positive for T21, one of which was confirmed by an antenatal karyotype, and the other was confirmed at birth. The third case did not undergo an invasive procedure and was not confirmed at birth (false positive). In one case, cfDNA testing was positive for T18 and was confirmed by an antenatal karyotype. There were no cases of trisomy 13 in the cohort. The no-call rate was 2.4% at first sampling. Fifty-eight (22.7%) women had embryo reduction, which in 40 (69%) of whom was performed after the cfDNA test result.ConclusioncfDNA testing could be offered as primary screening for main fetal aneuploidies in triplet pregnancies after provision of appropriate patient information. What's already know about this topic?Detailed information on the performance of non-invasive prenatal screening (NIPS) in triplet pregnancies is limited and there are several factors that make it more challenging. Clarification is needed on the performance of NIPS for triplet pregnancies.What does this study add?NIPS in triplet pregnancies has successfully detected cases of trisomy 21 and 18 NIPS in triplet pregnancies has a low failure rate (2.4%) The performance of cell-free DNA analysis encourages its implementation as primary screening to reduce the number of invasive procedures in triplet pregnancies.