Cell-based non-invasive prenatal testing for monogenic disorders: confirmation of unaffected fetuses following preimplantation genetic testing

Christian Liebst Frisk Toft,Ulrik Schiøler Kesmodel,Inge Søkilde Pedersen,Kristín Rós Kjartansdóttir,Ann Nygaard Jensen,Mathias Kølvraa,Marianne Louise Vang Østergård,Line Dahl Jeppesen,Katarina Ravn,Henrik Okkels,Birte Degn,Helle Smidt Mogensen ,Ida Vogel,Anja Ernst,Hans Jakob Ingerslev,Ripudaman Singh,Richard Farlie,Inga Baasch Christensen,Palle Schelde,Steffen Sommer,Bolette Hestbek Nicolaisen,Niels Uldbjerg,Lotte Hatt

doi:10.1007/s10815-021-02104-5

Abstract

PurposeProof of concept of the use of cell-based non-invasive prenatal testing (cbNIPT) as an alternative to chorionic villus sampling (CVS) following preimplantation genetic testing for monogenic disorders (PGT-M).MethodPGT-M was performed by combined testing of short tandem repeat (STR) markers and direct mutation detection, followed by transfer of an unaffected embryo. Patients who opted for follow-up of PGT-M by CVS had blood sampled, from which potential fetal extravillous throphoblast cells were isolated. The cell origin and mutational status were determined by combined testing of STR markers and direct mutation detection using the same setup as during PGT. The cbNIPT results with respect to the mutational status were compared to those of genetic testing of the CVS.ResultsEight patients had blood collected between gestational weeks 10 and 13, from which 33 potential fetal cell samples were isolated. Twenty-seven out of 33 isolated cell samples were successfully tested (82%), of which 24 were of fetal origin (89%). This corresponds to a median of 2.5 successfully tested fetal cell samples per case (range 1–6). All fetal cell samples had a genetic profile identical to that of the transferred embryo confirming a pregnancy with an unaffected fetus, in accordance with the CVS results.ConclusionThese findings show that although measures are needed to enhance the test success rate and the number of cells identified, cbNIPT is a promising alternative to CVS.Trial registration numberN-20180001

Highlights

Preimplantation genetic testing (PGT) allows for the selection and transfer of unaffected embryos from patients carrying or affected by a hereditary disorder
Eight different genes markers used for preimplantation genetic testing for monogenic disorders (PGT-M) and cell-based non-invasive prenatal testing (cbNIPT) as well as the results and conclusions from PGT, cbNIPT, and chorionic villus sampling (CVS). b short tandem repeat (STR) profiles from cbNIPT including paternal and maternal profiles
CbNIPT confirmed the transfer of an unaffected embryo, which was confirmed by CVS analysis (a). bp, base pair; cbNIPT, cell-based non-invasive prenatal testing; CVS, chorionic villous sampling; Mb, mega bases; PGT, preimplantation genetic testing; PGT-M, PGT for monogenic disorders; STR, short tandem, CxSy, case x sample y were affected, one gene in each case, of which six were of maternal origin

Summary

Introduction

Preimplantation genetic testing (PGT) allows for the selection and transfer of unaffected embryos from patients carrying or affected by a hereditary disorder. Prenatal testing, with the aim of verifying the PGT result to allow for termination of pregnancy in case of a misdiagnosis, is recommended by the ESHRE consortium guidelines [2]. The current gold standard for prenatal testing following PGT is CVS, which is an invasive procedure associated with a small risk (< 0.2%) of miscarriage [3]. Approximately 50% of patients undergoing PGT choose not to opt for prenatal follow-up by CVS despite recommendations and counselling on the (low) risk of misdiagnosis associated with PGT. The reason(s) for declining CVS are unknown, but they likely include factors such as fear of the procedure, risk of miscarriage, and unwillingness to opt for termination of pregnancy in the case of an affected fetus. A non-invasive alternative to prenatal follow-up is likely to increase patient acceptance of confirmatory prenatal testing

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Discussion

Conclusion