Blastocyst, transfer
In 1992, a team of Doctors from NUH put Singapore on the fertility world map when they implanted and delivered the worlds first Blastocyst Transfer Baby. Since then Blastocyst Transfer has become a popular procedure amongst couples who are trying to get pregnant.
What is a blastocyst?
A blastocyst is an embryo that has developed about 5 days after fertilisation. By this time it has developed from a single cell to a hollow ball of cells, with a ‘clump’ of cells in the cavity. Blastocysts have a very thin outer layer and therefore do not require assisted hatching, so they are more likely to get implanted into the uterine cavity and therefore result in a successful pregnancy.
What’s the difference between a blastocyst transfer and a traditional embryo transfer?
Traditionally, embryos are transferred to the uterus on the second or third day of development after in vitro fertilisation. In a blastocyst transfer, embryos are cultured in the laboratory for five to seven days after fertilisation.
So what?
Transferring embryos at the blastocyst stage, allows the highest chance for pregnancy. Blastocyst transfer is associated with around a 50% success rate, compared to the usual 35%.
It is also deemed as more natural, as the transfer occurs at day 5 or 6, which is approximately the time an embryo would normally arrive in the uterus. Alternatively, during Day 3 transfers, embryos are placed inside the uterus at a time when they should normally still be in the fallopian tubes.
Because of the two day delay, there is also a higher chance of selecting chromosomally normal embryos. Majority of abnormal embryos do not develop past the 8-cell stage. Therefore, extending culture to the blastocyst stage may mean that more of the surviving blastocysts available for transfer may have normal chromosomes.
It also keeps the risk for multiple pregnancy low, as fewer embryos need to be transferred.
If you experience a multiple pregnancy you are at increased risk for miscarriage, stillbirth, and having low birth weight babies. Most couples choose to avoid these dangers by undergoing the blastocyst transfer procedure
Disadvantages of blastocyst transfer
One major drawback is the reduced chance to freeze the other embryos. Blastocysts do not survive the freezing process as well as Day 3 embryos do. Couples may choose to freeze their embryos so they can attempt at another chance if this fails.
If you choose to have a blastocyst transfer, also expect to lose quite a few of your embryos. On average, only 50% of embryos may develop to the blastocyst stage. Patients with few eggs, embryos or poor developing embryos may end up not having any blastocyst for transfer.
While the overall risk of having a multiple pregnancy is reduced, the risk for monozygotic (identical) twins is increased following blastocyst culture. This is inline with most articifial reproductive treatments. A recent study showed that you are also 2 to 5 times more likely to become pregnant with identical twins after receiving fertility treatment than after natural conception.
Ultimately blastocyst transfer is also more expensive There is an extra fee of around Singapore $500-$700 for couples who wish to use blastocyst transfer above what is normally charged for IVF/ICSI.
