Embryo Transfer - day 5 versus day 3 transfer

In Vitro Fertilization – Blastocyst embryo transfer.

For couples who are undergoing In Vitro Fertilization (IVF) treatment  in the Los Angeles area , there are many new medical terms as well as treatment options that are usually discussed by the Reproductive Endocrinology and Infertility (REI) specialist. One of the most important decisions during the IVF process is the decision of when to transfer the embryos back into the uterus.

During the In Vitro Fertilization process the ovaries are stimulated with medications in order to grow multiples eggs. Those eggs are visualized during the transvaginal sonogram as “follicles”.  When the follicles reach a specific size and are considered “mature” an additional medication (called “the trigger shot) is administered in order  to induce the release of the eggs into the follicular fluid  and 36 hours later the aspiration of the eggs is performed. Once the eggs are retrieved, they are fertilized with the partner’s or donor sperm and the resulting embryos are kept in culture media in the laboratory until the embryo transfer day.

The embryos consist initially of a few cells.  As the embryo grows in the laboratory, those cells keep multiplying and dividing. At the same time the shape of the embryo also changes and transforms from a relatively simple accumulation of cells ( “cleavage stage” embryo) to a more  elaborated form called “blastocyst”. The blastocyst is already differentiated into  different compartments, some of which will give rise to the placenta while other compartments will develop into the actual embryo/fetus.

During the IVF process the embryos can be transferred into the uterus in a few different stages of their development: in some European countries embryos are transferred at an early stage, during the first or second day of their life. In the US embryos are usually transferred back into the uterus in two potential stages:

• Cleavage stage embryo : third day of the embryo’s life, also called “day 3 transfer”.
• Blastocyst stage: fifth day of the embryo’s life, also called “day 5 transfer”.

There is still an ongoing debate in the scientific world on the ideal time to transfer the embryos. Some fertility centers perform all embryo transfers on day 3 while other fertility centers perform all embryo transfers on day 5. Here at the Center for Fertility and Gynecology ,we believe that the ideal time to transfer the embryos should be based on the patient’s characteristics as well as the underlying diagnosis.

What are the advantages and disadvantages of a day 5 embryo transfer compared to a day 3 embryo transfer?

The most significant advantage of growing the embryos in the laboratory to the blastocyst stage is the ability to select the strongest embryos, embryos that have a higher chance of implantation and as a result, a pregnancy.  In fact many embryos that are of low quality and/or genetically abnormal are less likely to survive for five days in the laboratory and are less likely to develop to the “blastocyst” stage. Multiple studies have shown an advantage of performing a “day 5 transfer” for patients that produce many embryos. In fact in selected patients with good response to medications and multiple embryos, a day 5 transfer resulted in a higher pregnancy rate. Unfortunately this advantage was not clearly found when a day 5 embryo transfer was performed on  women of older age and/or women that produce a low number of eggs/embryos ( women with diminished ovarian reserve). For those women there was not a clear advantage of performing a day 5 embryo transfer compared to a day 3.

Disadvantages of a day 5 embryo transfer compared to a day 3 embryo transfer:

• Higher risk of cycle cancellation with no embryos to transfer. When a day 5 embryo transfer is applied to women of older age and/or with only a few embryos, there is a higher chance that none of the embryos will survive to the fifth day and no embryo will be left to perform the embryo transfer.
• Higher risks of having fewer embryos or no embryos at all to freeze for future transfers.
• Slightly increased risk of identical twins.
• Slightly higher risk of having a male child.
• Concern about increase risk of identical twins.

In conclusion, a day 5 embryo transfer in young women who produce multiple embryos can increase pregnancy rate by allowing to select the best quality embryos on day 5 while for women of older age with reduced number of embryos,  this advantage is not very clear.

If you have any questions regarding IVF or embryo transfer please contact Paula at paula@center4fertility.com