What is IUI?

What is IUI, a.k.a., Intrauterine Insemination?

6 min read

If you’ve been trying to get pregnant and have been unsuccessful for 12 months or more (six months if you’re over 35 years old), one of the first type of fertility treatments your doctor may suggest is intrauterine insemination or IUI.

What is IUI?

An IUI is a procedure that includes “washing” a semen sample to remove seminal fluid, debris and dead sperm cells so you end up with a more concentrated and healthier collection of sperm (often called the post-washing sample). That sperm is then introduced directly into the uterus using a catheter.

This may improve the odds of conception by:

  • Providing a better-quality sperm sample
  • Cutting down the travel distance for the sperm to meet the egg (only about one percent of sperm will make it from the vagina, past the cervix and into the uterus with regular intercourse—the IUI allows the sperm to bypass the first gate)
  • Timing the IUI procedure near ovulation (this is why it’s routinely done along with cycle monitoring)

When might IUI be used?

An IUI is usually the first step in using advanced reproductive technologies, meaning that before jumping straight to IVF (in-vitro fertilization) your clinic may require or suggest that you try a few IUI cycles first. Here are a few common reasons why IUI might be recommended:
  • Low sperm counts or poor sperm motility. An IUI delivers sperm much further up the female reproductive tract so they don’t have to swim as far to get to the egg. The sperm wash also helps by removing certain barriers like debris, dead cells and abnormal sperm.
  • Sexual dysfunction. If the male partner is unable to ejaculate during intercourse or if the female partner has a pelvic condition or pain that limits her ability to have intercourse, an IUI is a good workaround.
  • Using donor sperm. If you’re using a donor sperm sample, an IUI injects the sperm exactly where it needs to go.

Generally, an IUI is focused on the sperm; trying to get better sperm closer to the egg around the right time. But, intrauterine insemination can often be paired with procedures to address other issues. In female patients over 35 most clinicians will also attempt to stimulate the ovaries (controlled ovarian stimulation) due to decreased egg quality (which happens naturally with age) in an attempt to release more eggs with each cycle, and increasing the chances of success (with a higher risk of multiples as well).

What is the IUI process?

  1. Deciding natural cycle or ovarian stimulation. Based on different variables (key among them, age), your doctor may suggest a natural cycle IUI (aiming for one egg at a time) or ovarian stimulation IUI (aiming for multiple eggs at a time). If you are stimulating the ovaries, you will be prescribed some oral medications (Letrozole, Clomid) or injections (Gonadotropins, Gonal F, Puregon).

  2. Cycle monitoring. After calling your clinic to report day-one of your cycle, you’ll get booked in for your first cycle monitoring visit which typically includes bloodwork and an ultrasound to help track your hormone levels and the growth of your ovarian follicles (one of them is going to mature into an egg!). If you are undergoing ovarian stimulation IUI, this is typically when you would start medications, and then be monitored to see their response. You’ll likely have a few appointments in these first two weeks of your cycle. You may also be asked to use LH test strips at home to catch the LH hormone peak that triggers ovulation.

  3. Ovulation. Timing the meeting of the sperm and egg is critical, so it’s common to use a trigger shot in an IUI cycle. This is a hormone injection that causes ovulation to occur (releasing the egg from the follicle). If your doctor is unsure whether your natural LH peak will cause ovulation to occur, or if you’re unable to capture an LH peak with your at-home testing, your clinic will give you a trigger shot and tell you exactly when to use it. Your clinic team will be monitoring the growth of your ovarian follicles. When the dominant follicle is mature (reaching about 16 to 24 millimetres) and your endometrial lining is thickened, you’ll be instructed on when to use the shot and when to return to the clinic for the IUI procedure. (Each clinic has its own specific policies on when to trigger the dominant follicles, the timing of the IUI in relation to the trigger medication, and even whether to perform one or two IUI procedures (on back-to-back days).

  4. Insemination. IUI day! This is the day your sperm sample is prepared (either from fresh or frozen). If a fresh sample is being used, the partner producing the sample will be asked to abstain from ejaculating for about two days, and collection can often be done either at home (if you live close enough to the clinic) or on site in a private room. The sperm sample is washed (which includes combining the semen with specific fluids that act like a filter and centrifuging the semen sample several times to separate the best sperm) and then inserted into the uterus using a soft, thin catheter. The whole procedure takes about five minutes and shouldn’t require any pain medication.

  5. Two-week wait and pregnancy test. In some clinics progesterone support is routinely recommended. If you are prescribed progesterone, this is the phase when it’s started (the luteal phase after ovulation). About two weeks after the IUI procedure you’ll return to your clinic for a pregnancy blood test. It’s important not to test early at home—the trigger shot contains hCG, the human pregnancy hormone which can linger in your system for up to 10 days, so any positive at-home test could show a false positive.

    What medications are common in IUI cycles? 

    • Follicle growth stimulators: If your ovaries need a little help growing those follicles and prompting the development of a dominant follicle (egg) your doctor might use medications to support egg growth. Letrozole is a commonly used oral medication taken for a few days at the start of your cycle (usually around cycle days five to nine). It’s an aromatase inhibitor which means it slows the conversion of testosterone to estrogen. Lower estrogen levels at this part in your cycle prevents follicle stimulating hormone (FSH) from being turned off, allowing more FSH to reach the follicles during their growth stage. After Letrozole is stopped, estrogen levels rise back up, assisting with egg maturation. 
    • Trigger shot: As described above, this is an injection that will cause the dominant follicle to release the egg (ovulation). It must be timed perfectly, so make sure to follow your clinic’s directions for using this one.
    • Uterine lining support: Progesterone (either injections or vaginal suppositories) are commonly started after ovulation to help support the endometrial environment and an early pregnancy (declining progesterone is what causes the lining to shed and bring on a menstrual period).

    What are the success rates with IUI?

    Success rates for any fertility treatment will vary depending on individual circumstances, including pre-existing conditions, age, sperm count and quality and the treatment protocol or medications used. For IUIs, the average success rate falls between 10 to 15 percent per treatment cycle. As a general rule, you can be expect to be more successful if the fertility issue is around intercourse (erectile dusfunction) instead of an egg issue. A healthy couple who have high quality sperm and eggs (but are unable to have intercourse), is likely to have a successful IUI within a few cycle attempts.

    What’s the difference between IUI and IVF?

    In an IUI cycle, the meeting of sperm and egg is helped, but there is still an element of chance, and fertilization happens in the fallopian tubes. In an IVF cycle we don’t leave the meeting of the sperm and egg to chance. The goal is to grow multiple dominant follicles (instead of just one or a few, which requires medications), retrieve the mature eggs from the ovaries (taking them out of the body), inject those eggs with a healthy-looking sperm, hope that fertilization takes place and then incubate them to support embryo development. Healthy, viable embryos (typically five days post-fertilization) can then be transferred into the uterus, or frozen and saved to be transferred in another cycle.

    For the best odds, your doctor will want the ovaries to grow multiple dominant follicles and not let ovulation happen naturally, so there are typically more medications used in IVF than in an IUI cycle. This process can take longer than an IUI since it’s often done as two cycles: egg retrieval and embryo transfer. In general, IVF success rates are much higher than IUI cycles, but also more expensive, and include more medications and side effects.