What is a blastocyst?

A blastocyst is the embryo stage around day 5–6, showing differentiation into inner cell mass and trophectoderm.

Why blastocyst transfer?

Transfer at blastocyst stage allows better embryo selection and may improve implantation rates while reducing multiple pregnancy risk.

Supporting techniques

Include embryo culture systems, time-lapse monitoring and assisted hatching when indicated. Time‑lapse monitoring, PGT and vitrification for frozen blastocyst transfer are commonly integrated to optimise outcomes.

Frequently Asked Questions

Day 3 transfer involves transferring embryos that have typically divided into 6-8 cells. Day 5 transfer, or blastocyst transfer, includes transferring embryos that have developed into a more advanced stage with hundreds of cells and distinct structures. Day 5 embryos have greater developmental potential in the lab.

Studies have consistently shown that the success rates of Day 5 vs Day 3 transfer are generally higher, particularly in patients with a good prognosis and a sufficient number of good-quality embryos. Blastocyst transfer allows for better embryo selection and higher implantation potential due to improved synchronization with the uterine environment.

Not all embryos will reach the blastocyst stage. This is a natural selection process where only the most robust and developmentally competent embryos are likely to reach the blastocyst stage in vitro. The extended culture period allows for this natural selection, identifying embryos with the highest developmental competence and implantation potential.

Blastocyst transfer, when done with single embryo selection, actually reduces the chances of twins. Modern fertility practices often recommend single blastocyst transfer to minimize the risk of multiple pregnancies and their associated complications. The transfer of a single high-quality blastocyst can achieve excellent pregnancy rates while reducing the risks associated with multiple gestations.

The embryo transfer procedure is relatively simple and non-surgical. A thin, flexible catheter is used to gently deposit the selected blastocyst(s) into the uterine cavity under ultrasound guidance. Most patients experience minimal discomfort during the procedure. The risks associated with blastocyst transfer are very low, including a small risk of uterine perforation or infection. Patients are usually advised to rest for a short period after the transfer.