FERTILITY, IVF AND REPRODUCTIVE GENETICS: Edited by Emre Seli and Juan Antonio García VelascoChallenges facing contemporary preimplantation genetic screeningJuneau, Caroline; Franasiak, Jason; Treff, NathanAuthor Information aReproductive Medicine Associates of New Jersey, Basking Ridge bRutgers, Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA Correspondence to Nathan Treff, PhD, Reproductive Medicine Associate of New Jersey, Rutgers, Robert Wood Johnson, 140 Allen Road, Basking Ridge, NJ 07920, USA. Tel: +1 973 656 2831; fax: +1 973 871 1226; e-mail: email@example.com Current Opinion in Obstetrics and Gynecology: June 2016 - Volume 28 - Issue 3 - p 151-157 doi: 10.1097/GCO.0000000000000270 Buy Metrics Abstract Purpose of review Aneuploidy is a leading cause of pregnancy failure. Although initial attempts to perform preimplantation genetic screening did not improve outcomes, validated techniques were developed to safely and effectively increase pregnancy rates. Still, many embryos designated as euploid do not implant. Current approaches are being refined to provide additional biologic insight into why this is the case. At present, the diagnosis and clinical relevance of segmental aneuploidy and mosaicism are amongst the more heavily investigated. Recent findings Class I data have proven the safety of trophectoderm biopsy and validation studies have shown single nucleotide polymorphism array and quantitative PCR can accurately detect whole chromosome aneuploidy. Similar studies to validate next generation sequencing are underway. Although randomized control trials have demonstrated the clinical utility of preimplantation genetic screening, recent data on the impact of mosaicism and segmental aneuploidy require clarification. Summary Several well powered randomized control trials have shown preimplantation genetic screening improves implantation rate. Plausible explanations for euploid failures include undetected mosaicism and segmental aneuploidy. However, the true incidence and dispersion of mosaicism within the embryo is unknown. Likewise, the resolution of detection and clinical significance of segmental aneuploidy is unclear. Further research to validate proposed detection algorithms and class I data to determine if detection impacts outcomes is needed. Copyright © 2016 YEAR Wolters Kluwer Health, Inc. All rights reserved.