Inclusion Criteria:  Women undergoing IVF or ICSI with controlled ovarian stimulation with gonadotrophins and the intention to treat by either transfer of a single fresh embryo on day 5 or in case of a freeze all cycle, the first rewarmed embryo. Age: Up to and including the 42nd completed birthday on the day of randomization. Has at least two early blastocysts on day 5.  Exclusion Criteria:  Treatment involving donated eggs Intention to perform any form of preimplantation genetic testing The use of IMSI or polarized light in the ICSI process The use of assisted hatching prior to randomization Previous participation in this RCT Where the cycle is carried out for fertility preservation If a day 2-4 transfer is planned Has a reduced likelihood of obtaining two early blastocysts on day 5 as evidenced by either: an AMH level of <3pmol/L or AFC <5 (if available)