Treatment & preservation · In plain English

Blastocyst

An embryo at a later early-development stage, commonly reached around five or six days after fertilisation.

Why you might see this term

In IVF, a clinic may discuss whether an embryo has reached this stage before transfer or freezing.

What to keep in mind

Reaching the blastocyst stage does not guarantee implantation, a chromosomally typical embryo or a live birth.

Sources & further reading

Prepared by ProFertility · Updated 23 October 2026.

Educational information based on the linked sources. This explanation is not an individual diagnosis or a treatment recommendation. A term appearing here does not mean the test is necessary or included in a particular kit.

Suggest a correction or ask a question →

Looking up another word?

You can search by abbreviation, full name or everyday language.

Back to the fertility A–Z →