After 48 hours, when pre-embryos usually consist of two to four cells each, they are ready to be placed into the woman's uterus. This procedure is known as embryo transfer. This is often done in a clinic or office on an outpatient basis. No anesthesia is used, although some woman may wish to have a mild sedative. The patient lies on a table or bed, usually with her feet in stirrups.
Some clinics perform the transfer with the patient in the knee-chest position.
Using a vaginal speculum, the doctor exposes the cervix. One or more pre- embryos suspend in a drop of culture medium are drawn into a transfer catheter, a long, thin sterile tube with a syringe on one end. Gently, the doctor guides the tip of the loaded catheter through the cervix and deposits the fluid into the uterine cavity. One or more embryos may be transferred during this procedure. The doctor and patient make the decision to use cryopreservation in advance.