At Arizona Center for Fertility Studies, Intrauterine Insemination (IUI) in done in the following manner.
Once the couple decides on going with a natural cycle versus a stimulated cycle, she calls on day 1-2 of her cycle and gets a screening vaginal ultrasound to rule out any ovarian cysts. If cysts are present, the IUI cycle is cancelled and she is offered birth control pills to get rid of the cysts. If no cysts are present, which is almost 100% of the time, than Clomid or HMG is started on the appropriate day of the cycle and ultrasounds are done every 2-3 days to monitor follicular (egg) numbers and development.
Once the follicles are mature, at least 18 mm in size, 10,000 IU of hCG is given to trigger ovulation. This will start the process of ovulation, or the release of the egg(s), predictably and very accurately, in about 38 hours. In human females, the process to actually release the egg takes about 4 hours. Therefore, 38 plus 4 equals 42, which is about the time the egg(s) will physically be released and picked up by the fallopian tube.
IUI, with the already washed sperm received 2-4+ hours earlier, is then placed into the uterine cavity using a small specialized catheter that is passed through the vagina and cervix. For the most part, there is minimum to no discomfort, however, a few women can experience mild cramping, and if they already know this, can take either Motrin, Alleve or Advil about a hour prior to the procedure.
The timing of IUI is critical, because there is a lot of evidence in the literature suggesting the sperm do not live in the uterus and only travel through it. Sperm, on the other hand, can live in the cervical mucus for an average of 3-4 days and from there travel up to the fallopian tube. It is estimated that sperm put in the uterus travels through it within 4-6 hours and afterwards it is all gone. If IUI is timed with anything other than the hCG trigger shot, there is a good probability that by the time ovulation occurs, and the egg is picked up by the fallopian tube, all the sperm are gone.
Examples of this would be:
If IUI was timed with the over the counter ovulation detection kits (ODK). Once the ODK turns positive, ovulation will occur in 26-40 hours. If IUI is done too soon or too late, by the time the fallopian tube picks up the egg(s), all the sperm may have already travelled out of the uterus and you will not be successful.
If IUI is timed with basal body temperature charts (BBT), by the time the temperature goes up indicating ovulation, the egg was released 36 hours earlier. Using BBT to time IUI is not much better than guessing when to do the insemination.
Timing IUI to when you think you should be ovulating, i.e. day 14 of a normal 28 day cycle or 16 of a normal 30 cycle, is also not much better than guessing, since sperm only stay in the uterus for approximately 4-6 hours, and you can not be sure ovulation is occurring when you think it is.
The best way to accurately time IUI is with a hCG trigger with insemination 42-43 hours later. Anything else, has a low probability of success and may explain why many IUIs are not successful. At Arizona Center for Fertility Studies, all cycles of natural-IUI or SO-IUI are done with hCG trigger; and yes, until we figure out how to have the ovary take the weekends off, work on the weekends, if that is when you need your IUI.
Graphic representation of the mechanics of doing intrauterine insemination (IUI)