Optimizing Embryo Transfer Timing: Day 4 Versus Day 3 And Day 5 In Fresh ICSI Cycles, A Randomized Controlled Trial

A Randomized Controlled Trial

Abstract

Background: Most assisted reproductive technology (ART) cycles are transferred on day 3 or
day 5. Day 4 transfer is very uncommon practice in most ART centers. Day 4 transfer to the
patients and clinicians will increase the flexibility of the embryo transfer (ET) timing and
decrease the in vitro culture duration. Study objectives: This study aimed at comparing the
outcome of day 3, day 4, and day 5ET regarding implantation rate and chemical, clinical and
ongoing pregnancy rates.
Patients and Methods: a randomized controlled trial on 384 ICSI cycles. Patients were under
40 years complaining of primary infertility who at least had 10 retrieved oocytes were
randomized to three groups (128 each) on the day of oocyte retrieval for either day 3, day 4 or
day 5 ET. Severe male factor, PGT-A and freeze all cycles were excluded. The primary
outcome measure was the clinical pregnancy rate while, the secondary outcomes included
implantation rates, chemical pregnancy and ongoing pregnancy rates.
Results: No significant differences were observed among the 3 groups regarding demographic
data, semen parameters and number of cases with history of recurrent implantation failure.
Moreover, the number of retrieved oocytes, number of matured oocytes and fertilization rate
were comparable. Day 4 and day 5 ET had comparable clinical pregnancy rates(60.2% and
62.5% respectively). However, the clinical pregnancy rate was significantly lower in day 3
group (46.9%). The same finding was also found in the chemical and ongoing pregnancy rates
in which, day 4 and 5 ET had comparable outcomes while day 3 ET was significantly inferior
to them.
Conclusion: Day 4 (morula) transfer is as good as day 5 (blastocyst) transfer regarding
clinical and ongoing pregnancy rates. Offering day 4 ET will increase the flexibility of the
embryo transfer policy in the ART clinics without compromising the cycle outcomes.
Keywords: ICSI, Embryo transfer, Day 4 transfer, Day 5 transfer, Morula, Blastocyst.