Shortly after the implementation of Comprehensive Chromosome Screening (CCS) techniques for Preimplantation Genetic Screening (PGS) came the transition in biopsy timing. Trophectoderm biopsy is meant to overcome the limitations of cleavage stage biopsy and single cell analysis.

The investigators have recently introduced this new approach and a frozen-thawed policy of euploid blastocysts is routinely performed.

This is a single centre retrospective study in patients undergoing a PGS cycle. The aim of the study is to assess the results obtained in a PGS programme after the implementation of a new biopsy timing and transfer policy. Results obtained in PGS cycles with blastocyst biopsy and frozen-thawed embryo transfer were analysed in comparison to cycles with cleavage stage biopsy and fresh blastocyst transfer.

Inclusion Criteria:

• Own gametes
• PGS for: advanced maternal age, repeated implantation failure, recurrent miscarriages, severe male factor, and previous affected pregnancies

Exclusion Criteria:

• PGS cycles with gamete donation
• Altered karyotypes
• Combined Preimplantation genetic diagnosis (PGD)+PGS cycles

Patients undergoing a PGS cycle with own gametes for any of the following indications: advanced maternal age, repeated implantation failure, recurrent miscarriages, severe male factor, and previous affected pregnancies.