The Embryo Transfer

Transferring embryos to the womb (uterus) is one of the most delicate and critical procedures in the in vitro fertilization (IVF) process. It is usually performed on an outpatient basis with minimal sedation.

The physician uses a catheter and syringe guided by ultrasound to deposit the embryos in the uterus. If the womb is in a certain position that makes it difficult to see, it may be necessary for the woman to have a full bladder during the procedure.

Between one and six embryos may be transferred, depending on the woman’s age and the stage of embryonic development. Some doctors perform transfers after day 3 of embryo development, when the embryo has six to eight cells. Advances in the laboratory culture of embryos have enabled doctors to offer the option of waiting until day 5, when the embryo has developed into a blastocyst. As the embryos grow, the laboratory changes the culture media in the petri dishes to better mimic the environment of a woman’s reproductive tract. The customized nutrients help the embryos develop into blastocysts which may have higher rates of implantation.

Transferring several embryos increases the risk of producing a multiple pregnancy. Thus, implanting fewer embryos greatly reduces the possibility of triplets or higher order multiples.

Although embryos with the most even appearance and least fragmentation are more likely to attach to the uterine wall, less regular-looking embryos may still result in healthy babies.

After the transfer, most women are prescribed progesterone to increase the chance of implantation, which occurs three to four days after transfer.