Live birth rate is significantly higher after blastocyst transfer than after cleavage-stage embryo transfer when at least four embryos are available on day 3 of embryo culture. A randomized prospective study.

Introduction: In a randomized controlled trial, we assessed whether pregnancy outcome would be improved by extending embryo culture to day 5 and transferring a blastocyst in patients with at least four good-quality embryos on day 3.

Methods: Multifollicular ovarian stimulation was performed with a GnRH agonist in 44% of patients and with a GnRH antagonist in 56%. Overall, 164 patients younger than 37 years fulfilled embryo quality criteria (at least four having at least six cells on the morning of day 3, maximum 20% anucleate fragments) on the third day of culture and were randomized to the day 3 (n = 84) or day 5 (n = 80) groups.

Duration of gonadotropin-releasing hormone antagonist administration does not affect the outcome of subsequent frozen-thawed cycles.

The duration of administration of GnRH antagonist in cycles stimulated with recombinant FSH for IVF/intracytoplasmic sperm injection does not affect the probability of blastocyst replacement and of achieving an ongoing pregnancy in subsequent frozen-thawed cycles.