Prenatal cell-free DNA screening for chromosomal aneuploidies after euploid embryo transfer shows high concordance with preimplantation genetic testing for aneuploidy results and low positive predictive values.

OBJECTIVE

To evaluate the positive predictive value (PPV) of prenatal cell-free DNA (cfDNA) screening for chromosomal aneuploidies in pregnancies achieved either after single euploid transfer in in vitro fertilization or Preimplantation Genetic Testing for Aneuploidy (PGT-A) cycles or transfer of single untested embryo, and to assess the concordance of prenatal-cfDNA-screening and PGT-A results.

DESIGN

Single center retrospective cohort study.

SETTING

Fertility clinic.

PATIENT(S): A total of 2,973 prenatal-cfDNA-screening results for the most common trisomies (T13, T18, T21, X, and Y) and microdeletions (1p36, 4p16.3, 5p15.2, 15q11.2, and 22q11.2) from singleton pregnancies allocated into two groups: PGT-A group (n = 1,204) pregnant after single euploid transfer and non-PGT-A group (n = 1769) pregnant after transfer of single untested embryo, between 2016 and 2023.

INTERVENTION(S): Not applicable.

MAIN OUTCOME MEASURE(S): The primary outcome measure was the accuracy of prenatal-cfDNA screening. Positive and negative prenatal-cfDNA-screening results and subsequent prenatal or postnatal diagnostic testing were used to classify each positive prenatal-cfDNA-screening result as a true or a false positive. Secondary endpoints were to evaluate the concordance of PGT-A and prenatal-cfDNA-screening results and to assess the differences in the fetal fraction of cfDNA used for prenatal-cfDNA-screening reports between the study groups.

RESULT(S): Prenatal-cfDNA screening was performed at a mean 11.3 ± 1.8 weeks gestational age, and yielded results in 99.9% of the patients (0.1% cancellation rate). There was no difference in the fetal fraction between PGT-A tested and not tested pregnancies (9.5% ± 4% vs. 10.3% ± 4%). 13 positive prenatal-cfDNA-screening results (two T21, two X0, four XXX, one XYY, one indeterminate sex, two 22q11 del/dup, and one 15q11.2del) were received for PGT-A group. Only one (22q11 dup) was confirmed with amniocentesis and fetal autopsy, giving a PPV for an abnormal prenatal-cfDNA screening of 7.7%, the rest had results concordant with PGT-A. Sex chromosomes were 100% concordant between prenatal-cfDNA-screening and PGT-A results, giving a 100% PPV for PGT-A for sex chromosomes and 100% negative predictive value for aneuploidies. Positive prenatal-cfDNA-screening results were received for 27 pregnancies from untested embryos (1.5%), follow-up testing was electively performed for 21, and 8 had confirmed the prenatal-cfDNA-screening result, giving a PPV for the non-PGT-A group of 38%.

CONCLUSION(S): This study demonstrates that patients undergoing in vitro fertilization/PGT-A and single euploid embryo transfer can reliably do prenatal-cfDNA screening during their first trimester. Fetal fraction in singleton pregnancies after PGT-A tested embryos is not different from pregnancies with untested embryos. Positive predictive value for an abnormal prenatal-cfDNA-screening result after euploid embryo transfer was reassuringly low (7.7%). PGT-A reliably selects against aneuploidy with 100% concordance with fetal sex.