The rationale behind sequential embryo transfer is that, during the first day-3 transfer, the embryos (1 or 2 embryos) may induce an increase in endometrial receptivity, thereby creating a better endometrial environment for the second transfer (1 blastocyst) on day 5.
Repeated failure of in vitro fertilization treatment is haunting to the patients and their clinicians. Patients who fail treatment repeatedly in spite of good quality embryos pose a special therapeutic challenge.
A policy of sequential or consecutive transfer on Day 3 and Day 5 embryos in patients with adequate number of retrieved oocytes ,yields the advantages of a good embryo implantation rate, satisfactory pregnancy rate and an acceptable multiple pregnancy rate at the same time avoiding complications of blastocyst transfer like cancellation of the transfer cycle and higher multiple order births. Blastocyst transfer is an approach aiming to improve the IVF outcome in repeated IVF failures. However, the results of this approach depend on the number of fertilized oocytes and the quality of the fertilized embryos. Thus, sequential transfer approach has the advantage of blastocyst transfer without exposing the whole cycle to the risk of cancellation.
Under the assumption that embryos that cease to develop in utero, result in implantation failure, growing them to the blastocyst stage will serve two goals. First, it will enable better selection of embryos for transfer and second it will promote more physiologic synchronization with the endometrium and capability of achieving the “implantation window”.
The transfer of embryos that are grown to the blastocyst stage helps in overcoming the problem of random selection of impaired embryos, healthy embryos are transferred and there is decreased risk of multiple pregnancies. However, it is possible that no blastocyst forms during culture with the risk of cycle cancellation. So this is an approach that is only suitable for patients who produce many embryos. The rationale behind sequential embryo transfer is that, during the first day-3 transfer, the embryos (1 or 2 embryos) may induce an increase in endometrial receptivity, thereby creating a better endometrial environment for the second transfer (1 blastocyst) on day 5.