Progesterone-modified natural cycle preparation for frozen embryo transfer.

Research Question: Is there any difference in clinical outcomes between the progesterone-modified natural cycle (P4mNC) and hormone replacement therapy (HRT) endometrial preparation protocols after single euploid blastocyst frozen embryo transfer (FET) cycles?

Design: A retrospective cohort study was performed at a single, private, high-volume fertility centre. Patients who underwent single euploid blastocyst FET between January 2017 and December 2019 were included. A total of 1933 FET cycles were reviewed, and 723 FET cycles from 548 patients met the inclusion criteria.

Chromosomal, gestational, and neonatal outcomes of embryos classified as a mosaic by preimplantation genetic testing for aneuploidy.

Objective: To understand the clinical risks associated with the transfer of embryos classified as a mosaic using preimplantation genetic testing for aneuploidy.

Design: Analysis of data collected between 2017 and 2023.

Setting: Multicenter.

Two clinical case reports of embryonic mosaicism identified with PGT-A persisting during pregnancy as true fetal mosaicism.

The health risks associated with transferring embryos classified as mosaic by preimplantation genetic testing for aneuploidies (PGT-A) are currently unknown. Such embryos produce PGT-A results indicating the presence of both euploid and aneuploid cells and have historically been deselected from transfer and grouped with uniformly aneuploid embryos as 'abnormal'. In recent years, numerous groups have reported the intentional transfer of mosaic embryos in the absence of uniformly euploid embryos, largely observing births of seemingly healthy babies.

Neonatal and clinical outcomes after transfer of a mosaic embryo identified by preimplantation genetic testing for aneuploidies.

Research Question: Do clinical and neonatal outcomes differ between mosaic embryo transfers (MET) and euploid embryo transfers (EET)?

Design: This retrospective cohort study compared the implantation rate, live birth rate (LBR) and miscarriage rate between 513 euploid embryos and 118 mosaic embryos (72 whole chromosome mosaic [WCM], 40 segmental mosaic and six complex mosaic). Blastocysts were analysed using preimplantation genetic testing for aneuploidies with next-generation sequencing, followed by a single vitrified-warmed embryo transfer. Trophectoderm biopsies were classified as mosaic if they had 20-80% abnormal cells.