Transfer of blastocysts and morulae on day 5

To limit the number of embryos transferred and reduce high-order multiple pregnancies without compromising a patient's opportunity to become pregnant.

Retrospective, nonrandomized analysis of embryo development and patient outcome when embryos were transferred on day 5.

Private practice.

Women undergoing in vitro fertilization (IVF) treatment.

Extend embryo culture to day 5 before embryo transfer (ET) to reduce the number of embryos transferred and minimize high-order multiple pregnancies.

Clinical pregnancy rate (CPR), implantation rate (IR), and live born rate (LBR) from expanding (expanded blastocysts and blastocysts) and nonexpanding (early blastocysts and morulae) embryos transferred on day 5.

Approximately 60% of patients had expanding embryos (EXE) on day 5. Forty percent of patients having an ET had transferable non-expanding embryos (NEE). Patients with EXE had higher CPR and LBR compared to patients with NEE. Implantation rate and multiple pregnancy rate (MPR) were also higher for patients with EXE. The miscarriage rate (MCR) for patients with EXE and NEE was not different. Approximately 5.5% of patients did not have an ET, with most (>98%) of the ET failures from patients with <==3 two pronuclei (2PN) embryos. The number of 2PN embryos had an effect on CPR, LBR, MPR, and the number of patients having cryopreservation.

Day 5 ET allows for the selection of embryos with the highest implantation potential as evidenced by acceptable pregnancy rates for patients with either EXE or NEE, without the need to transfer more than two embryos.