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 (which is often used in connection with in vitro fertilization (IVF), may be used in humans or in animals, in which situations the goals may vary.

Embryo transfer can be done at day two or day three, or later in the blastocyst stage, which was first performed in 1984.Factors that can affect the success of embryo transfer include the Endometrial receptivity, Embryo quality and Embryo transfer technique.

John Edmond Buster (born July 18, 1941) is an American physician who, while working at the University of California at Los Angeles School of Medicine, directed the research team that performed the first embryo transfer from one woman to another resulting in a live birth. It was performed at the Harbor-UCLA Medical Center, reported in July 1983, and culminated in the announcement of the birth on February 3, 1984. In the procedure, an embryo that was just beginning to develop was transferred from the woman in whom it had been conceived by artificial insemination to another woman who gave birth to the infant 38 weeks later. The sperm used in the artificial insemination came from the husband of the woman who bore the baby.Buster and other members of the UCLA research team were featured in People Magazine, and Time Magazine. Building upon Buster's research, over 200,000 live births resulting from donor embryo transfer have been recorded by the Centers for Disease Control(CDC) in the United States.Buster continues to practice medicine as a reproductive endocrinologist at Women and Infants' Fertility Center in Providence, Rhode Island.