Myth: Only Day 5 blastocyst can result in successful pregnancy

Myth: Only Day 5 blastocyst can result in successful pregnancy

Following fertilisation, an embryo becomes a blastocyst when it develops cells forming an outer trophectoderm, an inner cell mass and a blastocoel cavity that is filled with fluid. A selection of viable blastocysts is typically taken on the fifth day of embryo culture and the remaining ones are discarded due to the common belief that they will probably not establish a successful pregnancy.

Not all embryos develop at the same development rate. Some embryos develop more slowly and may only form blastocysts on the seventh day of embryo culture. In such cases, these embryos may have been discarded prematurely when in fact they could have gone on to be just as viable as those taken earlier and still result in a healthy live birth.

At Alpha IVF, we believe that ‘Only Day 5 blastocyst can result in successful pregnancy’ is a myth that should be debunked. At our clinic, all embryos are given an equal chance to fully realise their potential, including those that take longer to develop into blastocysts. Instead of giving up on them, our meticulous team of embryologists will give all embryos a chance to form into blastocysts, up to the seventh day after fertilisation.

The Evidence:

In a study paper, Euploidy Rate of Day 7 Blastocysts Derived From In-Vitro Fertilisation,  presented at the presented at 16th International Conference on Preimplantation Genetics 2017, Valencia, Spain, Alpha IVF demonstrated that 7 seventh-day blastocysts out of 15 taken from 12 patients were viable after preimplantation genetic screening. This represented a 46.7 euploidy rate, meaning that nearly half could potentially go on to achieve a healthy pregnancy.

These preliminary results conclusively showed that Day 7 blastocysts can be chromosomally normal and should be considered for embryo transfer.

In another study paper, Live births following Day 7 Blastocyst Transfer after Preimplantation Genetic Testing for Aneuploidy (PGT-A), presented at the 18th International Conference on Preimplantation Genetic Diagnosis 2019, Geneva, Switzerland, Alpha IVF demonstrated Day 7 blastocysts can be euploid and yield healthy live babies.


With Alpha IVF’s strong ability to culture embryos, we can routinely select blastocysts until the seventh day after fertilisation and have shown several successful live births after transferring euploid Day 7 blastocysts. This gives our patients a better chance of pregnancy with viable embryos that would otherwise not have been transferred at all.

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