In Vitro Fertilization
Blastocyst Transfer
What is a blastocyst?
A blastocyst is an embryo which has progressed to a stage where it begins to form a fluid filled core. This usually occurs 5-6 days after ovulation and is a critical part of embryo development.
What is a blastocyst transfer?
This is the placement of blastocysts into the uterus.
Why is a blastocyst transfer performed?
Embryos which have progressed to the blastocyst stage are more likely to result in pregnancy than are embryos at earlier stages (day 2, 3 or 4 embryos). This is thought to be due to natural selection of the embryos, meaning that the embryos that have progressed in culture to the blastocyst developmental stage have proven that they are the healthiest embryos of the group and capable of surviving and growing to the blastocyst stage.
Will I get a blastocyst transfer?
Ideally all women would get a transfer with embryos which have progressed to the blastocyst stage. However, blastocyst transfer is not suitable for all women.
The day of embryo transfer depends on the number and quality of embryos available on the third day after the eggs are harvested from the woman.
If a woman has 4 or more high quality embryos on the third day after egg harvest, she is likely to have blastocysts two days later. If the woman is >35, or has few high quality embryos on the third day after transfer, she is less likely to have blastocysts two days later. A day 3 embryo transfer is often more appropriate for these women.
What are the advantages of blastocyst transfer?
A blastocyst transfer allows for the selection of embryos which have the highest chance of resulting in pregnancy. This means we can generally put fewer embryos back into the uterus while maintaining excellent pregnancy rates.
What are the risks and disadvantages of blastocyst transfer?
The major disadvantage of blastocyst transfer is the possibility that no embryos will progress to this stage. This may occur for many reasons such as an embryo being genetically abnormal, or because it may not tolerate the artificial culture system. In these cases, a day 3 embryo might have resulted in higher pregnancy rates. This scenario cannot be predicted unless a couple has done IVF before.
There is also a question of whether Imprinting Disorders are more common in embryos cultured to the blastocyst stage. As with ICSI, it is uncertain whether the culture conditions or the infertility diagnosis is the cause of this suspected risk. Either way the risk of imprinting disorders is rare.
The final disadvantage of blastocyst transfer is that Assisted Hatching (AH) is more risky because it may elevate the risk of identical twins.