IUI is an acronym for IntraUterine Insertion. Sperm are put into the uterus via the cervix. They travel to the tubes, where fertilization takes place. Poor quality sperm can bypass the journey through the vagina and avoid the cervical mucus, which may be hostile. IUI can be combined with IVF.
IVF is an acronym for In Vitro Fertilization. The eggs are retrieved (withdrawn) from the ovary via a needle put into the abdominal wall. The man provides sperm which is mixed with the egg in a test tube (culture dish), and put in an incubator. After fertilization occurs, the resultant embryos are injected into the woman's uterus. IVF bypasses the tubes, and is appropriate in cases of tubal obstruction.
GIFT is an acronym for Gamete IntraFallopian Tube Transfer. The egg and sperm are collected as above, and then injected directly into the woman's oviduct. They are not fertilized in a culture dish. Fertilization occurs naturally within the tube, and the egg then travels down to the uterus. GIFT involves the tubes, and is appropriate only if they are healthy.
ZIFT is an acronym for Zygote In Vitro Fertilization, (a zygote is an embryo). ZIFT is a variation of both GIFT and IVE Sperm are "washed", and then mixed with the egg in a culture dish, where fertilization takes place. The resultant embryo is injected into the oviducts instead of the uterus. ZIFT involves the tubes, and is only appropriate if they are healthy.
PZD is an acronym for Partial Zona Dissection. It is a new technique to help feeble sperm get through the egg's outer wall. The egg is retrieved and pierced in two places to create a tiny passageway. The sperm can then get in easily. PZD has led to 7 pregnancies so far, and could raise the odds for infertile men.
The implantation rate with GIFT and ZIFT is higher than IVF. It seems that transferring the 2-day-old embryo to the uterus might act like an IUD; it might set up an irritation factor which interferes with implantation. Multiple births occur with in vitro fertilization because the more embryos in the uterus, the better the chance of one implanting. Selective selection involves removing the weaker embryos to give the others a better chance. For some parents-to-be and physicians, selective selection can be a difficult problem involving issues of ethical and moral choice.