Pregnancy occurs with sexual intercourse. On penetration and ejaculation, the sperm cells swim their way to the vagina, to the cervix, to the uterus, and finally reach one of the fallopian tubes. The sperm meets the mature egg and undergoes fertilization and thus an embryo is formed. However, IUI is independent of the natural migration of the semen from the vagina to its final destination for fertilization. Instead, in IUI, the sperm is directly implanted in the appropriate site at the appropriate time during the ovulation window with the help of a catheter. The only similarity between IUI and natural conception is that the fertilization process is allowed to happen naturally in the body.
Everythings you wanted to know about conception