embryotransfers

Embryo transfer is a procedure in assisted reproductive technology in which one or more embryos are placed into a female's uterus with the aim of achieving pregnancy. It is most commonly used in conjunction with in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).

Two main types are used: fresh embryo transfer, performed in the same cycle as egg retrieval, and frozen embryo transfer (FET), in which previously created embryos are thawed and transferred later. Clinicians may transfer a single embryo to reduce the chance of multiples or two or more embryos in an attempt to raise success rates; donor embryos can also be used.

The procedure is usually performed with ultrasound guidance. A catheter carries one or more embryos through the cervix into the endometrial cavity. After a fresh transfer, luteal-phase support with progesterone is commonly given to improve implantation. For FET, the endometrium is prepared with hormones to be receptive at the time of transfer.

Success varies with maternal age, embryo quality, and uterine health. Younger patients generally exhibit higher implantation and ongoing pregnancy rates. Embryo quality and freezing methods also influence outcomes, and some programs favor single-embryo transfers to reduce multiple gestations.

Risks include multiple pregnancy when more than one embryo is transferred, bleeding, infection, or rarely uterine injury. There are also emotional, ethical, and financial considerations, and cycles may be canceled or fail. Embryo transfer is a central component of ART and may involve donor eggs or surrogacy; it is also used in veterinary medicine for animal breeding.