IntraUterine insemination (IUI), also called artificial insemination, is the oldest assisted reproductive technique. One resource states that unsuccessful attempts were made in the 1400's to artificially inseminate the wife of King Henry IV of Castile. IUI started in laboratories with animal testing. In 1742, fish eggs were successfully fertilized by Dutch scientists. The first mammal, a dog, was inseminated in 1780 by Italian scientists. Human insemination began in the late 18th century and became a more common procedure during the 19th century. The first successful human pregnancy from IUI of frozen sperm was in 1953. Medical advances such as ovarian stimulation and development of medical equipment have improved pregnancy outcomes in recent years. More finite scientific understanding of the reproductive system has also added to IUI success rates.
Today, IUI involves depositing a concentrated amount of motile sperm, which have been washed free of seminal plasma, into the uterus. This is done as close to the time of ovulation as possible. By 1987, US physicians were performing 172,000 women per year with 65,000 resulting births. It remains the most widely used technique worldwide today. IUI is a popular choice for infertile couples because of the relatively low cost and procedure simplicity.