An embryo transfer is the last part of the in vitro fertilization (IVF) process. At Fertility Centers of New England, all embryos are grown for 5 days to the Blastocyst stage prior to transfer into the uterus. Many patients ask what happens during embryo transfer?
What Happens During Embryo Transfer?
Early in the morning, on the 5th day after insemination, all of the embryos are analyzed under a microscope by the embryologist; those embryos that have already differentiated into fetal and placental tissue; both the fetal and placental tissue are graded. At this point the top quality Blastocysts are prepared for either embryo transfer or cryopreservation.
Does Assisted Hatching Boost Pregnancy Success During IVF?
In the case of an embryo transfer, one or two blastocysts are loaded into a very thin catheter with a small amount of media and a small air bubble. This catheter is then brought into the doctor to perform the embryo transfer into the uterus. In certain cases a procedure called assisted hatching is performed just prior to the embryo transfer. Assisted hatching is a technique that helps an embryo release from its outer shell to allow implantation in the uterus for pregnancy. Using a laser, a small hole is placed into the outer shell of the embryo to help it “hatch” out of the shell and improve implantation rates.
Embryo Freezing or Cryopreservation
Any top quality Blastocysts which are not transferred are then vitrified. This a form of cryopreservation, which involves replacing the water in the cells with an inert substance. These embryos are then placed into the liquid nitrogen for storage. We will also cryopreserve embryos on the 6th day of growth if they meet certain criteria.
Preimplantation Genetic Testing
In certain cases, embryos are not directly cryopreserved but are biopsied prior to cryopreservation. In these cases of preimplantation genetic testing, top quality blastocysts are placed under a microscope and a few placental cells, that are distant from the fetal tissue, are removed using a small pipette. These cells are placed into a small test tube and sent for to an outside lab for genetic testing. The embryo is then cryopreserved via vitrification. The cryopreserved blastocysts are stable for many years.
When a patient returns to use her cryopreserved embryos, the embryos are warmed, and water returns to the cells in the embryo. The embryo is allowed to expand and then are prepared for transfer. Thawing the embryos takes place a few hours before the transfer. All of our cryopreserved blastocysts undergo assisted hatching prior to their transfer.
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