Embryo transfer refers to a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy. This technique is often used in connection with In-vitro Fertilization (IVF). Embryo transfer can be done at day two or day three, or later in the blastocyst stage, which was first performed in 1984.
Uterine Preparation: For the procedure, uterine lining (endometrium) needs to be appropriately prepared, so that the embryos can implanted. In a natural cycle, the embryo transfer takes place in the luteal phase at a time where the lining is appropriately undeveloped in relation to the status of the present Luteinizing Hormone. In a stimulated or a cycle where a ‘frozen’ embryo is transferred, the recipient woman could be given first estrogen preparations (about 2 weeks), then a combination of oestrogen and progesterone so that the lining becomes receptive for the embryo.