Embryo transfer is a medical procedure whereby one or multiple embryos are placed in the uterus of a woman in order to impregnate her. Embryo transfer is a part of the in vitro fertilization technique to assisted reproduction.
The embryos that are transferred into the uterus may be of two kinds:
i. Fresh embryos
ii. Frozen embryos
Fresh embryos are fertilized egg cells from a fresh menstrual cycle, while frozen embryos refer to the embryos that were taken from a previous cycle than the present one. These embryos are then cryopreserved and are thawed just before they have to be transferred. Before an embryo can be transferred, doctors prepare the recipient’s uterine lining. The transfer is done during the luteal phase. The luteal phase means that the lining of the uterus, at the time of embryo transfer, is undeveloped.
In case the doctors are using frozen embryos for transfer, the woman is given estrogen preparations for about 2 weeks, after which she is put on a combination of oestrogen as well as progesterone. This is done to make the uterine lining receptive of the embryo. This time is known as the implantation window in medical parlance.
In the actual process of embryo transfer, the doctors place a speculum inside the vagina in order to see the cervix. The cervix is then cleaned with the help of a saline solution. The embryo is filled inside a catheter, which is then inserted inside the uterine canal. Once the embryos have been planted inside the uterine canal, the catheter is withdrawn. Doctors usually perform an abdominal ultrasound to ensure that the embryos have been placed correctly inside the uterus.