Blastocyst Transfer
Blastocyst transfer is a type of embryo transfer where one or more embryos are transferred at the blastocyst stage of development. This usually occurs on the fifth day after follicular aspiration.
Frozen Blastocyst Transfer
Frozen blastocyst transfer involves transferring frozen blastocysts to the uterus. These embryos are at an advanced stage of development, which can increase the chances of successful implantation.
Fertilisation and Development of Embryos
After the doctor has removed the eggs from an ovary (follicular aspiration), they are fertilised in the laboratory. This is done either by normal in vitro fertilisation (IVF) or by means of intracytoplasmic sperm injection (ICSI).
Immediately after fertilisation, an egg starts to divide and develop into an embryo. The stages of development are as follows:
- Day 1: The pronuclear stage (fertilised egg)
- Day 2: Two- to four-cell stage
- Day 3: The eight-cell stage
- Day 4: The morula stage
- Day 5: The blastocyst stage
Embryo Transfer
The doctor usually inserts one or more embryos in the woman’s uterus two to three days after egg retrieval. This process is referred to as embryo transfer.
Blastocyst Transfer
The embryos can also develop in an incubator up to the fifth day, i.e. the blastocyst stage, thanks to improved cell culture media (blastocyst culture). If the doctor transfers such developed embryos into the woman’s uterus, this is referred to as blastocyst transfer.
Advantages of Blastocyst Transfer
Identification of Embryos with Development Potential
Only a small percentage of fertilised eggs develop into blastocysts. However, those that do have a higher chance of successful implantation. Therefore, blastocyst transfer allows for the identification of embryos with the most potential for successful implantation.
Ideal Timing of Transfer
The timing of blastocyst transfer is ideal since, in natural pregnancies, it takes around five days for the embryo to reach the uterus and implant. It is believed that the uterus is most receptive to implantation on this day, making it the perfect timing for blastocyst transfer.
Legal Background
Germany has strict regulations under the Embryo Protection Law regarding fertilised eggs. The law permits a maximum of only three fertilised eggs to mature to the blastocyst stage in an incubator. The law also prohibits the selection of embryos.
Selection of Embryos
Under the Embryo Protection Law, a decision on which of the fertilized eggs will be suitable for a blastocyst transfer is made on the first day after fertilization, during the pronuclear stage. The pronuclear stage is the period when the nuclei of the egg and sperm cells are not yet fused. During this stage, the cells are not yet embryos. Selecting embryos is not allowed.
Cryopreservation
If there are excess fertilised eggs during the pronuclear stage, they can be frozen using cryopreservation.
Success Rates of Blastocyst Transfer
The success rates of blastocyst transfer are commonly asked by couples undergoing fertility treatment. Here are some important details about this topic:
Increased Chances of Pregnancy
The chances of getting pregnant after blastocyst transfer are higher than that of embryo transfer at an early development stage. According to the German IVF-Registry Annual 2014, the odds are increased by around seven percent.
Success Rates by Age
Age plays a significant role in determining the success rates of blastocyst transfer. Women up to the age of 30 have a higher success rate of 45 to 50 percent compared to women aged 30-39 whose chance of success is between 35 to 40 percent.
Personalised Medical Approach
Blastocyst culture may not provide the same advantages for all women with low egg count and quality, as a day-3 transfer may be more beneficial. Therefore, reproductive medicine specialists will determine the best transfer method for each individual through a personalised medical approach for the best chance of success.