Single-nucleotide polymorphism (SNP)-based non-invasive prenatal testing (NIPT) can help predict a subset of submicroscopic abnormalities associated with severe clinical manifestations. Retrospective review of actual clinical practice for a SNP based NIPT for over 80,000 referrals for 22q11.2 deletion syndrome and over 42,000 referrals for 1p36, cri-du-chat, Prader-Willi, and Angelman microdeletion syndromes will be described. A revised protocol that reflexively sequenced high-risk calls at a higher depth of read will be presented. The revised protocol substantially reduces false-positive results and can provide positive predictive values comparable to that seen for fetal aneuploidies.

Targeted PCR based amplification is a universally used method in molecular biology with decades of experience and known levels of accuracy and can be used as a more flexible, faster and less expensive approach compared to WGA for DNA enrichment of embryonic biopsies. Defined genomic regions can be selected to perform aneuploidy testing and specific primers can be incorporated to simultaneously detect single gene mutations or for the assessment/diagnosis of multiple other clinical factors, such us polyploidy, uniparental disomy (UPD). In particular, qPCR based CCS allows for the accurate detection of whole chromosome aneuploidies only (maximize sensitivity of detection in PGT-A cycles), avoiding the risk of false positive results due to misinterpretation of WGA related amplification bias.

During current PGS practice aneuploid embryos are occasionally encountered and often these are the only embryos available for transfer. It is currently unclear whether mosaic embryos should be considered for transfer. General guidelines have been suggested by PGDIS and COGEN, but they do not provide a clear scoring system.
During the talk an evidence-based scoring system for prioritizing mosaic aneuploid embryos for transfer will be presented. It is based on a retrospective analysis of cytogenetic and molecular analysis in 72,472 chorionic villi samples and 3806 products of conception to assess the likelihood that mosaic aneuploidy in the placenta will result in fetal aneuploidy, clinically significant uniparental disomy or miscarriage. This tool based on the risk for these adverse outcomes can assist fertility experts in making clinical decisions and patient counseling.

OBJECTIVE: Focus groups were conducted with individuals involved in prenatal diagnosis to determine their opinions relating to whole exome sequencing in fetuses with structural anomalies.
METHOD: Five representatives of patient groups/charities (PRGs) and eight clinical professionals (CPs) participated. Three focus groups occurred (the two groups separately and then combined). Framework analysis was performed to elicit themes. A thematic coding frame was identified based on emerging themes.
RESULTS: Seven main themes (consent, analysis, interpretation/reinterpretation of results, prenatal issues, uncertainty, incidental findings and information access) with subthemes emerged. The main themes were raised by both groups, apart from 'analysis', which was raised by CPs only. Some subthemes were raised by PRGs and CPs (with different perspectives). Others were raised either by PRGs or CPs, showing differences in patient/clinician agendas.
CONCLUSIONS: Prenatal consent for whole exome sequencing is not a 'perfect' process, but consent takers should be fully educated regarding the test. PRGs highlighted issues involving access to results, feeling that women want to know all information. PRGs also felt that patients want reinterpretation of results over time, whilst CPs felt that interpretation should be performed at the point of testing only
DECLARATION: The PAGE study is funded by the Welcome Trust (Health Innovation Challenge fund). to Hurles ME, Kilby MD, Chitty L, Maher E.

Currently, massively parallel sequencing is becoming broadly available in preimplantation, prenatal and postnatal diagnosis. Consequently, an increasing number of patients and apparently healthy individuals undergo whole exome sequencing which identifies a large number of variants. However, their disease liability is mostly not known and various software prediction tools have a limited utility. Proper assessment of their penetrance is thus important since the majority of databases assume disease association of variants based on their prevalence in clinically diagnosed cases. This ascertainment bias is particularly relevant in preimplantation and prenatal diagnosis. An international effort focused on the comprehensive penetrance analysis in cystic fibrosis (www.cftr2.org) may serve as a model for other initiatives of this kind.

We offer an ISO 15189:2012 accredited service for non-invasive prenatal diagnosis (NIPD) for single-gene disorders at our National Health Service (NHS) Regional Genetics laboratory based at Great Ormond Street Hospital, London. Since 2013 we have offered a United Kingdom Genetic Testing Network (UKGTN) approved service for FGFR3-related skeletal disorders, including achondroplasia and thanatophoric dysplasia. We also have UKGTN approval for FGFR2-related craniosynostosis, including Apert and Crouzon syndrome, and for paternal mutation exclusion for cystic fibrosis. We have expanded our service to improve availability of NIPD for couples at risk of single-gene disorder and to offer definitive diagnosis for cystic fibrosis.

Aneuploidy is the major genetic cause compromising pregnancy outcome, expressed either in viability failure and/or somatic and mental maldevelopment. The underlying molecular basis for the origin of aneuploidy is a matter of dispute between the roles of reduced cohesin complex and failure of microfibrils to properly attach to the centromere of chromosomes. More significantly, what has not been identified is the specific molecular components from either of these systems, each of which is comprised of multiple, integrated, interactive biochemical reactions. Specific examples will be cited. Defining the molecular processes leading to aneuploidy will provide entry to the control of chromosome distribution during meiosis and thereby, possible prevention of aneuploidy prior to conception.

Comprehensive chromosome screening (CCS) can be performed with a wide variety of amplification and analysis methods. While whole genome amplification (WGA) provided some success with SNP arrays, array CGH, and next generation sequencing, more contemporary methods of targeted PCR provide unique advantages and avoid the many associated pitfalls of WGA. These include the ability to perform reliable simultaneous analysis of genotypes for single gene disorders, contamination testing, and triplody prediction, and the ability to differentiate mosaicism more effectively. Furthermore, better reliability of targeted CCS substantially improves accuracy, workflow, and cost of performing testing.

Embryonic mosaicism has recently become the focus of growing attention and controversy in the context of PGS. In order to evaluate the extent of mosaic aneuploidy in clinical practice and to gain insights on the practices and views regarding this issue, we conducted a 20-item web-based questionnaire with questions related to mosaicism in PGS. A total of 102 IVF units from 32 countries performing 108,900 IVF cycles annually responded to the survey, representing both clinic which perform and those that do not perform PGS. The results of a web-based survey will be presented, emphasizing the ongoing debate and the urgent need for more robust data on PGS.