Supernumerary vitrified blastocysts can be effectively diagnosed after warming by fast qPCR-based aneuploidy testing and transferred without the need of a second vitrification round

Study question: Is qPCR-based chromosomal analysis on vitrified blastocysts with subsequent euploid single embryo transfer (SET) an efficient approach for patients needing preimplantation genetic diagnosis for aneuploidies (PGD-A)? Summary answer: In patients with previous fresh IVF-failure(s), supernumerary vitrified blastocysts can be effectively diagnosed after warming and transferred without the need of a second vitrification round. What is known already: PGD-A is a technique whose application in IVF treatments is constantly growing nowadays, while vitrification is a consolidated, safe and efficient strategy for oocytes/embryos cryopreservation. Since supernumerary embryo cryopreservation is a common strategy in IVF, many patients have a cohort of untested cryopreserved embryos. Thus, for patients with a history of fresh IVF failures and/or miscarriages, an attractive approach may involve the warming and chromosomal testing of those embryos with subsequent euploid SET Study design, size, duration: Longitudinal cohort study involving 51 patients (female age at oocyte retrieval:35.9 ± 3.5,23.6–42.0). Candidate patients had untested vitrified embryos from a previous IVF cycle and a history of IVF failures (1.4 ± 1.5,0–6) and/or miscarriages (0.5 ± 0.7,0–3). All PGD-A cycles on warmed blastocysts with subsequent euploid SET between April2013- October2016 were included. The primary outcome measure was ongoing pregnancy rate per euploid SET ( > 12 weeks of gestational age). Secondary outcomes included biochemical pregnancy loss and miscarriage rates Participants/materials, setting, methods: Trophectoderm biopsy was performed after warming and blastocyst full re-expansion. Chromosomal analysis was conducted by qPCR in 4 hours and subsequent euploid SET was performed with no need for a further vitrification-warming cycle. Clinical outcomes were compared to vitrified-warmed euploid SETs from 447 patients (female age:36.5 ± 2.8,25.6–44.0) undergoing PGD-A with an indication of history of IVF failures (1.9 ± 1.8,0–11) and/or miscarriages (0.7 ± 1.0,0–5) between April 2013-October 2016. Main results and the role of chance: 115 blastocysts survived warming (survival rate after warming: 98.3%; n = 115/117,95%CI = 93.9%-99.8%) and underwent trophectoderm biopsy after full re-expansion. No blastocyst degenerated after biopsy. 66 blastocysts were diagnosed euploid by qPCR and 40 subsequent euploid SETs were performed. 26 euploid blastocyst were revitrified. Ongoing pregnancy rate for the study group was similar to the historical control group, namely 42.5% (n = 17/40; 95%CI = 27.0%-59.1%) and 40.9% (n = 244/597; 95%CI = 37.7%-45.8%), respectively (NS). No differences between the two groups were also found for the biochemical pregnancy loss rates: 5.0% (n = 1/20; 95%CI = 0.1%-24.8%) and 7.7% (n = 23/300; 95% CI = 4.9%-11.3%) and miscarriage rates: 10.5% (n = 2/19;95%CI = 1.3%- 33.3%) and 11.9% (n = 33/277; 95%CI = 8.3%-16.3%) for the study group and the historical control, respectively (NS). Limitations, reasons for caution: Data are needed to assess implantation potential for those blastocysts undergoing a second round of vitrification. Vitrified oocytes or embryos cryopreserved at earlier preimplantation developmental stages were not included. Wider implications of the findings: Trophectoderm biopsy after warming and fast qPCR aneuploidy testing with subsequent euploid SET is an efficient strategy to rescue untested cryopreserved embryos when indicated. Trial registration number: none.