Characteristics of the IVF Cycle that Contribute to the Incidence of Mosaicism.

Highly sensitive next-generation sequencing (NGS) platforms applied to preimplantation genetic testing for aneuploidy (PGT-A) allow the classification of mosaicism in trophectoderm biopsies. However, the incidence of mosaicism reported by these tests can be affected by a wide number of analytical, biological, and clinical factors. With the use of a proprietary algorithm for automated diagnosis of aneuploidy and mosaicism, we retrospectively analyzed a large series of 115,368 trophectoderm biopsies from 27,436 PGT-A cycles to determine whether certain biological factors and fertilization (IVF) practices influence the incidence of overall aneuploidy, whole uniform aneuploidy, mosaicism, and TE biopsies with only segmental aneuploidy.

Segmental aneuploidy in human blastocysts: a qualitative and quantitative overview.

Background: Microarray-based and next generation sequencing (NGS) technologies have revealed that segmental aneuploidy is frequently present in human oocytes, cleavage-stage embryos and blastocysts. However, very little research has analyzed the type, size, chromosomal distribution and topography of the chromosomal segments at the different stages of development.

Methods: This is a retrospective study of 822 PGT-A (preimplantation genetic test for aneuploidies) performed on trophectoderm samples from 3565 blastocysts biopsied between January 2016 and April 2017.

Clinical application of embryo aneuploidy testing by next-generation sequencing.

We review here the evolution in the field of embryo aneuploidy testing over the last 20 years, from the analysis of a subset of chromosomes by fluorescence in situ hybridisation to the transition toward a more comprehensive analysis of all 24 chromosomes. This current comprehensive aneuploidy testing most commonly employs next-generation sequencing (NGS). We present our experience in over 130 000 embryo biopsies using this technology.

Correlations between Synaptic Initiation and Meiotic Recombination: A Study of Humans and Mice.

Meiotic recombination is initiated by programmed double strand breaks (DSBs), only a small subset of which are resolved into crossovers (COs). The mechanism determining the location of these COs is not well understood. Studies in plants, fungi, and insects indicate that the same genomic regions are involved in synaptic initiation and COs, suggesting that early homolog alignment is correlated with the eventual resolution of DSBs as COs.

New tools for embryo selection: comprehensive chromosome screening by array comparative genomic hybridization.

The objective of this study was to evaluate the usefulness of comprehensive chromosome screening (CCS) using array comparative genomic hybridization (aCGH). The study included 1420 CCS cycles for recurrent miscarriage (n = 203); repetitive implantation failure (n = 188); severe male factor (n = 116); previous trisomic pregnancy (n = 33); and advanced maternal age (n = 880). CCS was performed in cycles with fresh oocytes and embryos (n = 774); mixed cycles with fresh and vitrified oocytes (n = 320); mixed cycles with fresh and vitrified day-2 embryos (n = 235); and mixed cycles with fresh and vitrified day-3 embryos (n = 91).

Use of array comparative genomic hybridization (array-CGH) for embryo assessment: clinical results.

Objective: To review clinical outcomes after preimplantation genetic screening. Most methods of embryo viability assessment involve morphologic evaluation at different preimplantation developmental stages. A weak association between blastocyst morphology and aneuploidy has been described, supporting the basis for preimplantation genetic screening (PGS) for assessment of embryo viability.

Chromosomal abnormalities in embryos from couples with a previous aneuploid miscarriage.

Objective: To compare the incidence of chromosomal abnormalities in preimplantation embryos from couples undergoing preimplantation genetic screening (PGS) after previous aneuploid miscarriage after either natural conception (NC) or assisted reproductive technology (ART) versus fertile couples who underwent PGS for sex-linked diseases as a control group.

Design: Retrospective study.

Setting: IVF clinic.

Testicular sperm from patients with obstructive and nonobstructive azoospermia: aneuploidy risk and reproductive prognosis using testicular sperm from fertile donors as control samples.

Objective: To establish a baseline incidence of chromosomal abnormalities in testicular sperm of fertile men and to determine the best control sample for comparisons with azoospermic males to estimate their reproductive prognosis.

Design: Prospective study.

Setting: Infertility clinic.

Redefining advanced maternal age as an indication for preimplantation genetic screening.

In this retrospective study, the utility of preimplantation genetic screening (PGS) in patients with advanced maternal age is evaluated. The patient population consisted of women aged 38-44years and included in a regular IVF programme with or without PGS analysis. Transfer rate, ongoing implantation rate and ongoing pregnancy rate were the main outcome parameters measured.

Aneuploidies in embryos and spermatozoa from patients with Y chromosome microdeletions.

In patients with Y chromosome microdeletions and high percentage of numeric chromosome abnormalities detected by fluorescence in situ hybridization on sperm, a high percentage of abnormal embryos was observed compared with oligozoospermic patients without Y chromosome microdeletions, with a significant increase in the percentage of embryos with monosomy X. Differences in fertilization rates between the different patient groups were not observed; however, blastocyst rates were significantly impaired in patients with Y chromosome microdeletions.

Impact of different patterns of sperm chromosomal abnormalities on the chromosomal constitution of preimplantation embryos.

Objective: To evaluate the effect of sperm chromosome abnormalities--disomy for sex chromosomes and diploidy--in the chromosomal constitution of preimplantation embryos.

Design: Retrospective cohort study.

Setting: Infertility clinic.