IVF & Treatment Basics
A blastocyst is a Day 5 embryo — the stage at which it most closely resembles the embryo naturally reaching the uterus for implantation. Transferring then significantly improves the chance of a successful pregnancy.
Day 1: Fertilisation confirmed (two pronuclei visible). Day 2: 2–4 cell embryo. Day 3: 6–8 cell embryo (cleavage stage).Day 5: As development continues, the embryo will develop into a blastocyst, which is composed of the trophectoderm (placenta) and the inner cell mass (embryo) and has between 100 and 200 cells. Not all fertilised eggs reach blastocyst - typically 40–60% do. This is not a failure; it mirrors what happens naturally in the body.
A Day 5 blastocyst transfer also allows better synchronisation between the embryo and the uterine lining, which may improve the chances of implantation. Since the embryo has already shown its ability to continue developing in the lab, it gives the fertility team additional insight while selecting the most viable embryo for transfer.
Day 3 transfer has historically been common in India and globally. But evidence consistently shows blastocyst transfers have higher implantation rates per embryo transferred. The extended culture period acts as a natural selection process embryos that cannot develop to Day 5 would not have implanted successfully anyway. At Pluro, culturing to Day 5 (when clinically appropriate based on embryo numbers and quality) helps your doctor transfer the embryo most likely to result in a baby.
At Day 5, AI-assisted grading software may be used by Pluro’s embryology team to assess each blastocyst. The AI analyses morphological features expansion grade, ICM quality, trophoectoderm grade against thousands of reference embryos to produce a ranked score. This does not replace your embryologist’s judgement; it provides an additional data point to help select the best embryo for transfer. The benefit to you: the embryo your doctor chooses has been evaluated using a comprehensive assessment process.
Q: What if none of my embryos reach blastocyst stage?
A: This occurs in certain cycles, especially those in which there are lower numbers of eggs collected or when the quality of the eggs is poor. A Day 3 transfer may be recommended by your physician in future cycles.
Q: Is it safe to keep embryos in culture until Day 5?
A: Yes. Modern laboratory conditions (pH, temperature, oxygen levels, CO2) closely replicate the environment of the fallopian tube. There is no evidence that extended culture harms viable embryos.
Q: Can all fertility clinics culture to Day 5?
A: Not all clinics have the laboratory capability for consistent Day 5 culture. Ask specifically about blastocyst rates and laboratory conditions when evaluating clinics
his occurs in certain cycles, especially those in which there are lower numbers of eggs collected or when the quality of the eggs is poor. A Day 3 transfer may be recommended by your physician in future cycles.
Yes. Modern laboratory conditions (pH, temperature, oxygen levels, CO2) closely replicate the environment of the fallopian tube. There is no evidence that extended culture harms viable embryos.
Not all clinics have the laboratory capability for consistent Day 5 culture. Ask specifically about blastocyst rates and laboratory conditions when evaluating clinics.
