The Difference Between IUI and IVF

Common confusion results from the simple fact that IUI and IVF begin with the same letter "I." The processes are similar in that something is inserted in the uterine cavity. However, they differ markedly thereafter.

IUI stands for “intrauterine insemination”. This is the placement of washed sperm through a small straw into the uterine cavity. This very small, soft tube is inserted through the vagina, past the cervix, and placed where the baby is supposed to grow. This procedure is excellent when there are no obvious problems in the woman and when the sperm count is moderately low.

While it is true that only one sperm fertilizes an egg, it actually takes a whole gang of sperm with good movement (motility) to clean layers from around cells off the egg, so that a single sperm can attach to the egg shell and fertilize the egg.  Most sperm die in the vagina after intercourse, due to normal vaginal acidity.

IUI is not beneficial if the fallopian tubes are blocked, if the sperm count is extremely low, or if there are significant problems with the sperm motility or quality.

IUI has also been used in conjunction with medicines to augment ovulation. In couples with otherwise unexplained infertility, IUI is very helpful in some cases where some couples are so stressed that they are unable to have intercourse at the proper time of the menstrual cycle. IUI is also useful if the cervix is quite tight or if the cervix is lacking mucus (a slippery substance required to help the sperm swim safely from the vagina up into the uterine cavity).

IVF, In vitro fertilization, is an entirely different process. Unlike IUI which requires natural egg release, this requires retrieving eggs from the ovary by passing a needle through the vagina and into the ovary. These eggs are then paired with sperm in the laboratory, leading to fertilization and hopefully, embryo development. Embryos are then transferred back into the uterine cavity with a small straw, just like in the process of IUI. IVF is an excellent procedure when the patient has problems safely picking up an egg (blocked tubes, pelvic adhesions, or endometriosis), when the sperm counts are low, or when infertility is otherwise unexplained.