Blastocyst Transfer
In the early days of IVF, it was felt that it may be better to transfer the embryos to the womb as soon as possible as the majority of embryos did not survive beyond day 3, and so transfers were usually performed on day 2 or 3 after the egg collection. In a natural menstrual cycle, embryos do not usually reach the womb until around day 5 or 6 of development. In recent years, there have been many improvements in human IVF, including improvements to the culture media, which allows more embryos to grow in the IVF lab for longer.
As a result, transferring embryos at the blastocyst stage has become popular for certain groups of patients. It cannot be applied to all patients, as in some cases all of the embryos arrest and none make it to the blastocyst stage. Blastocyst transfer is most successful in cases where there are a good number of embryos on day 2 and 3, which gives more chance of obtaining some good quality blastocysts on days 5 or 6. Blastocyst transfer is a useful method of embryo selection for some patients.
