Day 3 embryo transfer with combined evaluation at the pronuclear and cleavage stages compares favourably with day 5 blastocyst transfer.
BACKGROUND
The respective advantages of day 3 and day 5 embryo transfer are a matter of debate. Previous comparisons did not include pronuclear stage zygote scoring and cumulative success rates (fresh and cryopreserved embryos).


METHODS
Patients were randomized prospectively for day 3 or day 5 embryo transfer. Day 3 embryos were selected for transfer and cryopreservation by using combined evaluation at the pronuclear and cleavage stages.


RESULTS
There was no difference between day 3 and day 5 fresh embryo transfers as to the rates of pregnancy (58 versus 62%), clinical pregnancy (56 versus 58%), delivery (50 versus 48%), implantation (35 versus 38%) and birth (33 versus 36%) rates. The corresponding values for cryopreserved embryo transfers were also similar. However, day 3 embryo transfer compared favourably with day 5 transfer when the pregnancy (90 versus 66%), clinical pregnancy (85 versus 62%) and delivery (77 versus 52%) rates were calculated per oocyte recovery attempt.


CONCLUSIONS
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.
Rienzi
Laura
L
Reproductive Medicine, European Hospital, Via Portuense 700, 00149 Rome, Italy. rienzi.laura@libero.it
Ubaldi
Filippo
F
Iacobelli
Marcello
M
Ferrero
Susanna
S
Minasi
Maria Giulia
MG
Martinez
Francisco
F
Tesarik
Jan
J
Greco
Ermanno
E
D000328:Adult; D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation; D036861:Delivery, Obstetric; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D009865:Oocytes; D036801:Parturition; D011247:Pregnancy; D018873:Pregnancy Rate; D013997:Time Factors; D020858:Tissue and Organ Harvesting; D017388:Zygote Intrafallopian Transfer