This monocenter academic study aims to evaluate the effectiveness and cost effectiveness of two different strategies: fresh Embryo Transfer (ET) on day 3 followed by cryopreservation of cleavage-stage (Day 3) embryos versus blastocyst-stage (Day 5) embryos.

The primary outcome is the cumulative pregnancy rate after all transfers (fresh and/or frozen embryo transfer cycles which might take about 1 year), up to two sequential cycles. The secondary outcome concerns a cost analysis of both strategies from the healthcare payer's perspective.

Inclusion Criteria:

• subfertile women planned for the first or second oocyte retrieval for in vitro fertilisation (IVF)/Intracytoplasmic sperm injection (ICSI) treatment
• who are older than 18 and less than 38 years old
• who have normal Follicle Stimulating Hormone (FSH) and normal Anti-Mullerian Hormone (AMH) levels

Exclusion Criteria:

• treatment with donor oocytes or donor embryos
• patients planned for Pre-implantation Genetic Diagnosis (PGD)
• Patients with BMI>30
• patients with endometriosis grade III-IV