Fetal DNA fingerprinting of DNA isolated from the peripheral maternal circulation at 9 gestational weeks allows precise identification of which embryos implanted following multiple embryo transfer

Abstract

OBJECTIVE: Embryonic DNA fingerprinting is a powerful tool that identifies which embryo implanted following multiple embryo transfer. Fingerprinting is integral to the validation of markers of reproductive competence. A problem with this method is the delay between IVF and access to fetal DNA at delivery. Amniocentesis or CVS provide fetal DNA, but are not done routinely. This study validates a method for fingerprinting fetal DNA obtained from the maternal circulation at 9 weeks gestation, reducing the time to confirm which embryo implanted by ∼31 weeks. DESIGN: Prospective, blinded. MATERIALS AND METHODS: Phase I: Determine fetal DNA levels that are detectable in the presence of maternal DNA: A series of mixtures of cell lines from siblings (46,XY and 49,XXXXY) and their mother were prepared. Each “childs” cell line (∼fetal DNA) was progressively diluted by the maternal cell line (∼maternal contamination). Microarray SNP profiles were created and concurrence levels determined for each sibling. Phase II: All embryos transferred to 5 patients with ongoing pregnancies were biopsied prior to transfer. Fetal DNA was enriched from the maternal plasma at 9 weeks gestation. Microarray SNP profiles were obtained on all specimens and from biopsies of non-transferred sibling embryos. SNP concurrence was calculated for all. Twins were treated as one fetus by analyzing SNPs with identical genotypes in both embryos. RESULTS: Phase I: The SNP pattern from mixture DNA was compared to the results from every combination of single cells from self and sibling. Clear separation was attained when 40% or more of the DNA was fetal in origin. Monosomy X was detected at 40% fetal DNA and tetrasomy X at 25%. Phase II: Self and sibling embryos were successfully distinguished by using enriched fetal DNA (P<0.01). CONCLUSIONS: This study demonstrates the first validated fetal DNA fingerprinting which discriminates sibling embryos at 9 weeks gestation. It also shows that this noninvasive method might be able to confirm the ploidy status of the fetus in the first trimester.Table 1% Similarity of maternal-fetal mixture to self or sibling single cell% of Fetal DNASelfSib00025004099.50.56010007599.50.510099.50.5 Open table in a new tab Table 2% Similarity of enriched fetal DNA to self or sibling embryosPatients# transferredTransferred (Self)Transferred (Sib-predicted)Non-transferred (Sib-known)1 (twins)262N/A382 (twins)276N/A243 (singleton)28120194 (singleton)25545475 (singleton)166N/A34 Open table in a new tab