A blastocyst is an embryo that has developed for five (sometimes six) days after fertilization. It has two parts: an inner cell mass, which becomes the baby, and an outer layer (trophectoderm), which is responsible for implantation and later forms the placenta.
In the laboratory, embryos are grown in special culture media that support them to day 5, and the best-developed embryo is then transferred to the uterus. Day-5 transfer mimics natural conception, where the embryo reaches the uterus at the blastocyst stage, just as the lining is ready to receive it.
Not every embryo reaches the blastocyst stage; typically around 40–50% of fertilized eggs do. This is not a loss caused by the lab: embryos that stop developing usually have chromosomal or developmental problems and would not have produced a pregnancy. Culturing to day 5 simply shows which embryos are most viable.
Why blastocyst transfer is now standard
- Higher implantation rate per embryo, so a single embryo can be transferred, avoiding the risks of twins.
- It allows genetic testing of embryos (PGT), which is done on day-5 blastocysts.
- It is particularly helpful after repeated failure with day-3 transfers.
International Guidelines
In line with global standards, Dr. Sabry follows the latest recommendations from the American Society for Reproductive Medicine (ASRM), European Society of Human Reproduction and Embryology (ESHRE), and Royal College of Obstetricians and Gynaecologists (RCOG). Thus, patients receive care that is safe, ethical, and evidence-based.
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Why Choose Dr. Ashraf Sabry?
Dr. Ashraf Sabry, consultant in obstetrics, gynecology, fertility, and aesthetic gynecology, is recognized among the best OBGYN and fertility specialists in Cairo. With over 20 years of experience, he combines science and compassion to provide world-class care. Book your appointment through the contact page, WhatsApp, or call +201022224442.