A blastocyst is typically a human embryo that’s 5-7 days old. But recently, 3 days old embryos are also transferred into the womb during IVF treatment. Most infertility specialists believe today that transferring better-developed embryos have better chance of getting a woman pregnant.
A blastocyst looks different to a day-3 embryo under the microscope. There’s a fluid-filled cavity in the middle called the blastocoel. Another area, housing a dense collection of cells, is called the inner cell mass and will become the foetus. A third assortment of cells, near the central cavity, will form the placenta.
Since every patient is different, a blastocyst transfer may be or may not be preferable to a day-3 transfer. But infertility specialists believe that a good embryo which survives for five days or more is probably more viable for implantation. A young embryo may not develop to five days and its future is harder to assess. So blastocyst transfers are usually more likely to succeed than transfers using younger embryos.
Blastocyst transfers are easier for implantation. In a non-IVF reproduction, a day-2 embryo will still be rolling down the fallopian tube towards the uterus. Transferring blastocysts is an easier prospect for highly receptive uterus. Additionally, genetic testing is more accurately carried out on blastocysts.
Blastocysts may lead to more IVF pregnancies in certain groups of women. Statistics reveal that live birth rates after blastocyst transfer are higher if you are under 35.
One of the cons of blastocyst transfers is that you may have fewer or no surplus embryos to freeze. IVF patients don’t usually go for a second attempt. The reason behind is that frozen embryo transfers, particularly those using blastocysts, are getting more successful.
Blastocysts can split, usually after transfer. Identical twins are not uncommon. Many couples can live with that. The most dramatic scenario is if both blastocysts split and progress to live births. The key point about blastocysts is that multiple births are less common than with younger transfers. The transfer of one good-quality blastocyst is often recommended.
In the past, infertility specialists might transfer up to four day-3 embryos and hope for the best. Blastocysts allow for more informed choices and better control over outcomes.