Authors: Rios C, JB Whitney, M VerMilyea, A Jones, A Picou, K Balloch, N Nugent, K Silverberg, RE Anderson, MC Schiewe.

Study question: Can NextGeneration sequencing (NGS) profile ranking of euploid embryos better predict eSET implantation potential of top quality blastocysts in contrast to morphological grading alone.

Summary answer: When blastocysts are both top quality and euploid, the lack of noise on a NGS profile adds no benefit for eSET compared to embryo grading.

What is known already: Blastocyst morphology assessment is the primary determinant for embryo transfer selection. Preimplantation genetic screening (PGS) now provides patients the ability to know the ploidy status of embryos before being transferred, which increases the implantation potential of eSETs. NGS provides every embryo a unique genetic profile which gives geneticists more information on genetic “noise” and low-level mosaicism that remains inconsistent between samples, patients, technicians and labs. Transferring mosaic embryos of differing profile levels has resulted in viable pregnancies, further questioning the clinical relevance of mosaic profiles. Furthermore, the risks to the offspring of a mosaic embryos is relatively unknown.

Study design, size, duration: Prospective randomized multicenter trial, initiated April 2016 and ended December 31, 2017. A total of 61 patients qualified for randomization by producing ≥ two top quality euploid day 5 or day 6 blastocysts. Upon enrollment, eSET selection was randomized between two pre-determined, double blinded ranking groups: Group 1 – embryologists ranked euploid blastocysts based on morphologic grade; and Group 2 – geneticists ranked transfer selection based on their interpretation of the NGS profiles.

Participants/materials, setting, methods: The study was performed at two locations (Clinic A: Newport Beach, CA; and Clinic B: Austin, TX) involving 6 physicians and differing embryology lab management and protocols. A single genetics lab performed NGS analysis using MiSeq (Illumina), with genetic noise/rank evaluated by a geneticist’s interpretation. All embryos were cultured through day 6, and trophectoderm biopsy and vitrification performed according to individual lab procedures. Implantation was measured by a visual sac and all pregnancies documented.

Main results and the role of chance: Eighty patients agreed to participate in this IRB approved study, however 19 (23.8%) failed to achieve inclusion criteria. Fifty-seven eSET’s have been performed to date. Group 1 (Morphology) achieved a 75.9% implantation and 62.1% ongoing pregnancy rate. Group 2 (Genetics) produced a 78.6% implantation and a 71.4 % ongoing pregnancy rate. There was no statistical difference (p>0.05) between either group for implantation, spontaneous abortion and/or ongoing pregnancy rate. Between clinics, clinic A accomplished a combined 96.7% implantation rate and 87.1% ongoing pregnancy, while clinic B had a 53.8% and 42.3% implantation and pregnancy rate, respectively. Clinic A exhibited no trends (p<0.1) between morphology and genetics, whereas clinic B revealed a preference for Group 2 (Genetics) for ongoing pregnancy. The latter finding that genetic profile ranking is associated with reduced miscarriage rates, warrants further investigation with a larger sample population. There were no significant differences between labs regarding fertilization rates, blastocyst yields or euploid rates. Patient age was not different between clinics, with a mean of 34 years old for qualifying participants. Clinic A had a single physician perform all stimulation and transfers, whereas Clinic B involved a rotation of 5 physicians for treatment.

Limitations, reasons for caution: Although sample size was low, it is important to note that patient selection was not biased, with study qualification requiring two top quality euploid blastocysts, not achievable for all IVF patients. Levels of mosaicism under 30% were classified as euploid and further scrutiny of extremely low levels was not performed.

Wider implications of the findings: Morphological grading has long been a standard for improving IVF success rates. With the adoption of NGS testing, more scrutiny of the PGS results has placed further importance on the role of the evaluating geneticist. This study indicates to the contrary, the embryologist is still vital for eSET embryo selection.