Day 3 embryo transfer with combined evaluation at the pronuclear and cleavage stages compares favourably with day 5 blastocyst transfer

Abstract

With a selected population of good prognosis patients and our embryo selection criteria, the implantation potential of day 3 and day 5 embryos is equal. Per oocyte recovery attempt, day 3 transfer is more clinically efficient than day 5 transfer, but at least one transfer of cryopreserved embryos is necessary to manifest this superiority.

Selection of Embryos for Day-3 Transfer at the Pronuclear-Stage and Pronuclear-Stage Cryopreservation Results in High Delivery Rates in Fresh and Frozen Cycles

“…These were higher than those reported in most blastocyst studies even though only 0.88, 0.80, and 0.61 more embryos were cultured for Groups I, II, and III, respectively, than the number transferred. Pregnancy and implantation rates with blastocyst transfer have ranged from 21 to 77% and 9-62%, respectively (2,5,6,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). With blastocyst transfer, all embryos are retained in culture to ensure at least two high-quality blastocysts are available for transfer.…”

“…With current cryopreservation techniques, human embryos survive and implant at higher rates when cryopreserved at the PN-S (8-10) compared with the cleavage or blastocyst stages (6,19,29,30). The cohort of fertilized oocytes from a retrieval cycle has better nuclear synchrony at the PN-S than do the embryos as they progress to later stages of development.…”

“…The percentage of patients with frozen embryos and number of embryos frozen are generally lower when all 2PN zygotes are held in culture and extra embryos are frozen at the time of transfer (6,17,22,29) than when extra zygotes are cryopreserved at the PN-S (8-10). With current culture techniques, only 30-50% of zygotes typically develop into normal blastocysts which results in fewer patients having cryopreserved embryos and fewer numbers of embryos frozen per cycle (2,(5)(6)(7)15,17,18,(20)(21)(22)25,27,29).…”

“…With current culture techniques, only 30-50% of zygotes typically develop into normal blastocysts which results in fewer patients having cryopreserved embryos and fewer numbers of embryos frozen per cycle (2,(5)(6)(7)15,17,18,(20)(21)(22)25,27,29).…”

“…Embryos with certain pronuclear-stage (PN-S) features, such as the presence of a halo and alignment of nucleoli within the PN, have better day-3 to day-6 cleavage rates and morphology and also implant at higher rates than embryos from zygotes lacking these features (1)(2)(3)(4)(5)(6)(7). Zygotes cryopreserved at the PN-S have high rates of cryosurvival and result in high pregnancy rates after post-thaw culture to the 4-to 6-cell stage (8)(9)(10).…”