PGT-A Versus Blastocyst Morphology Selection

Overview

Introduction Embryo aneuploidy is likely the leading cause of implantation failure in IVF cycles. Since the inception of IVF, non-invasive morphology based scoring has been the most widely used embryo selection method, resulting in relatively low embryo implantation rates. Our understanding of the optimal conditions required for in vitro embryo culture in IVF has advanced significantly over the past two decades. The implementation of improved in vitro embryo culture technologies (i.e., culture media and incubators) has resulted in an increase in the number of good quality embryos and consequently in increased numbers of blastocysts. While blastocyst transfers have seemingly improved the reproductive outcomes of IVF, they still remain suboptimal. The main objective of this randomized controlled trial (RCT) will be to investigate whether preimplantation genetic testing (i.e., PGT with comprehensive chromosome screening (CCS)) for aneuploidy is a superior embryo selection method, with the live birth outcomes of euploid blastocyst frozen embryo transfers (FET) compared with the LB outcomes of unknown-ploidy blastocyst FET, with blastocysts selected on (standard) morphological score. Methods This RCT will be conducted at a single private IVF centre performing routine segmented-IVF, with intracytoplasmic sperm injection (ICSI), blastocyst freeze-all, and artificial frozen embryo transfer (art-FET). Normo-ovulatory infertile patients, with maternal age ≤35 years and at least two blastocysts with a morphology score of 2BB cryopreserved, will be randomized by computer-generated randomized allocation to either the PGT or morphology arm of the trial. All transfers will be single embryo transfers (SET), with only the first FET cycles following freeze-all to be analyzed. Consent and Ethics Akdeniz University Medical Faculty Clinical Research Ethics Committee has approved the trial (reference number: 2015/399), with anonymized results to be released in ClinicalTrials.gov. All patients will provide informed consent, which included an agreement for the use of anonymised data for research and SET.

Introduction Embryo aneuploidy is likely the leading cause of implantation failure in IVF cycles. Since the inception of IVF, non-invasive morphology based scoring has been the most widely used embryo selection method, resulting in relatively low embryo implantation rates. Embryo morphology assessment methods have significant limitations (i.e., the assessments are subjective and the method uses fixed time-point assessments to define dynamic embryo development) and shortcomings (i.e., exposes embryos to sub-optimal conditions during assessment). Notwithstanding the limitations and shortcomings of this method its use worldwide has continued, because it is a relatively simple and non-invasive method and its scores have been shown to be (moderately) positively correlated to embryo euploidy, ongoing pregnancy, and live birth (Van Royen et al., 1999, Ahlstrom et al., 2011, Forman et al., 2013, Capalbo et al., 2014, Oron et al., 2014, Rhenman et al., 2015). However multiple gestations still represents one of the most significant complications in IVF, which are mainly the result of multiple-embryo embryo transfers, with multiple-embryo transfers used to overcome the relatively low embryo implantation rates in IVF. Our understanding of the optimal conditions required for in vitro embryo culture in IVF has advanced significantly in the past two decades. The implementation of improved in vitro embryo culture technologies (i.e., culture media and incubators) has resulted in an increase in the number of good quality embryos and consequently in the numbers of blastocysts. While blastocyst transfers have seemingly improved the reproductive outcomes in IVF, the use of SET and PGT technologies have revealed embryo implantation still to be sub-optimal (Schoolcraft et al., 2013). New CCS platforms are a major breakthrough in PGT, allowing 24-chromosome screening to be performed with high degree of accuracy from single cells (Harper and Harton, 2010). The evidence that morphology scores were only moderately associated with euploidy and that the transfer of PGT predicted euploid embryos resulted in higher implantation rates (Dahdouh et al., 2015), has seen the continued use of morphology-based scoring methods increasingly being challenged. In addition to all the other advances in IVF, significant improvements have also been made in cryopreservation technologies. These improvements have resulted in significant improvements in frozen-thawed embryo survival (i.e. minimizing of risks), post-thaw developmental competence (Cobo et al., 2012; Balaban et al., 2008), and in the reproductive outcomes of FET (Evans et al., 2014; Ozgur et al., 2015). The benefits of FET include; the transfer of embryos to a more physiologic endometrium (i.e., early luteal phase), the ability to time transfers more accurately, and the ability to use patient-specific endometrial preparations (Casper and Yanushpolsky, 2016, Franasiak et al., 2016; Groenewoud et al., 2013, Yarali et al., 2016). Moreover, the hypotheses of PGT requires to be confirmed in further robust RCT before its implementation in routine IVF. Objectives The primary objective of this RCT will be to investigate whether PGT for aneuploidy as a blastocyst selection method is superior to standard morphology scoring blastocyst selection, comparing the reproductive outcomes in FET cycles. The decision to transfer all blastocysts in FET will eliminate any potential impact of ovarian stimulation confounding on endometrial receptivity and to use freeze-all cycles will allow the use of the primary blastocysts of blastocyst cohorts. The primary outcome measure of this trial will be LB, with a LB defined as a pregnancy cycle delivering at \>20 weeks of gestation. Secondary objectives The secondary objective of the RCT will be to investigate whether euploid blastocyst transfer results in reduced miscarriage, with a miscarriage defined as a clinical pregnancy lost at \<20 weeks of gestation. Keywords: blastocyst; comprehensive chromosome screening; euploidy; frozen embryo transfer