Many of the couples I meet and discuss with either prior to a treatment cycle or during one have this question in mind: what is the difference between a blastocyst transfer and a day 3 transfer?
Embryo transfers can be performed between day 2 and day 5 of embryo culture. Embryos during these days develop from the 2-4 cell stage on day 2, to the 8 cell stage on day 3, to the morula stage on day 4 and finally to the blastocyst stage on day 5. This stage is the final developmental stage prior to endometrial implantation and the commencement of a pregnancy.
The day we choose to transfer embryos back into the uterus depends on many parameters:
- The number of embryos we have and their quality
- The endometrium
- The medical history of the patient
- The end goal number of embryos to transfer
The more days we culture embryos in the laboratory the more information we have about them. Therefore, in cases where we have a number of good quality Day 3 embryos, the best option is to carry on with culture. By doing this, we will have a better selection of late stage embryos to choose from. However, if you only have one or two embryos then extended laboratory conditions may affect their quality and therefore may reduce success rates. In these cases, it is better to transfer earlier.
Advantages of a blastocyst transfer
Some of the advantages of performing an embryo transfer at the blastocyst stage, instead of on Day 2-3 of embryo culture are:
- Better selection of the fastest growing embryos
- Higher success rates
- Lower chances of a multiple pregnancy, as in many cases we can even opt to transfer 1 embryo.
It is important to point out that by culturing embryos up to the blastocyst stage, the quality of the embryo does not improve. But it does mean that a more objective evaluation of the embryos is possible in order to choose the best ones to transfer.
Unfortunately, around 50% of embryos degenerate in laboratory culture and do not reach the blastocyst stage. We are not in the position to know whether these degenerated embryos might have survived to blastocyst if they had been in their natural environment, the womb, instead of the laboratory. This is the reason why culture and transfer at the blastocyst stage must only be used in selected cases.
At Newlife we run a successful blastocyst culture and transfer programme, in cases that meet specific indications. The final decision on whether to opt for extended culture and blastocyst transfer is made on day 3 of embryo development.
You can be sure that the medical and scientific staff of Newlife IVF has the knowledge and experience to try to ensure the best outcome for you.
Chrysa Karakosta, BSc, MSc
Chrysa is the Lab co-Director at Newlife IVF Greece, in Thessaloniki Greece, from the beginning of 2010 and now heads the International Patient Department.