Intrauterine insemination (IUI) is a fertility treatment where concentrated sperm is placed directly into the uterus through a thin tube, timed to coincide with ovulation. It’s typically the first treatment doctors recommend before moving to more intensive options like IVF, with pregnancy rates ranging from about 10% to 20% per cycle depending on age and the underlying cause of infertility.
Who IUI Is Recommended For
IUI works best for people with functioning fallopian tubes and specific, identifiable barriers to conception. The most common reasons doctors recommend it include cervical factor infertility (where cervical mucus or anatomy makes it difficult for sperm to reach the egg), moderate male factor infertility such as low sperm count or reduced motility, unexplained infertility, ovulation problems, and ejaculatory disorders. It’s also sometimes used for couples dealing with immunological infertility, where antibodies interfere with sperm function.
For same-sex couples and single parents using donor sperm, IUI is often the starting point because of its relative simplicity and lower cost compared to IVF.
How the Process Works
An IUI cycle has three main phases: stimulation, monitoring, and insemination. Before any of this begins, you’ll go through baseline testing. This typically includes a pelvic exam, uterine ultrasound, blood work, STI screening, and a semen analysis. Your doctor will also check that your fallopian tubes are open, usually with a specialized X-ray or ultrasound.
Once testing is complete, many IUI cycles begin with fertility medication to stimulate ovulation. Oral medications are taken for about five days early in your cycle, while injectable hormones may be used for up to two weeks. Some cycles are done without medication at all, relying on your natural ovulation. Your doctor will monitor follicle growth with ultrasounds and may trigger ovulation with a hormone injection when follicles reach the right size, typically around 16 millimeters or larger.
Timing is everything. Ovulation generally occurs 36 to 38 hours after a trigger shot, so insemination is usually scheduled 34 to 36 hours after the injection. If you’re not using a trigger shot, you’ll track your natural hormone surge with at-home ovulation kits, and insemination is scheduled accordingly.
The Insemination Itself
On the day of the procedure, the sperm sample is prepared in a lab. This “washing” process separates the healthiest, most motile sperm from the rest of the sample and removes substances like prostaglandins that could cause cramping. Labs use different techniques for this. In one common method called swim-up, sperm are given a culture medium to swim into, naturally selecting the strongest swimmers. Another approach uses density gradient centrifugation, which sorts sperm by density to isolate those with normal shape and movement.
The insemination itself takes just a few minutes. A thin, flexible catheter is passed through the vagina and cervix into the uterus, and the concentrated sperm sample is injected. Most people describe the sensation as similar to a Pap smear, with mild cramping at most. There’s no anesthesia needed and no required recovery time afterward.
Success Rates by Age
Age is the single biggest factor affecting IUI outcomes. In an analysis of over 4,200 insemination cycles, pregnancy rates per cycle broke down roughly as follows:
- Under 25: about 20% per cycle
- 25 to 29: about 13% per cycle
- 30 to 34: about 11% per cycle
- 35 to 39: about 9% per cycle
- 40 to 41: about 9% per cycle
- 42 to 43: about 6% per cycle
- Over 43: about 3.5% per cycle
One encouraging finding: for the first three cycles, women aged 40 and 41 had pregnancy rates comparable to those of women between 35 and 39. However, after three cycles, pregnancies in the 40-41 group became rare. For women under 40, rates remained relatively stable through six cycles, averaging between 5% and 15% per attempt. This is why most doctors recommend trying three to six IUI cycles before considering IVF.
How IUI Compares to IVF
The core tradeoff is cost versus effectiveness per cycle. IUI costs between $250 and $4,000 per cycle in the U.S., depending on your clinic, location, and whether medications are included. Oral fertility drugs add roughly $10 to $100 per month, while injectable hormones can add $1,000 to $3,500 per cycle. If donor sperm is needed, each vial runs $25 to $1,500.
IVF is significantly more expensive per cycle but delivers higher pregnancy rates. A full IVF cycle produces a live birth roughly 19% of the time across all ages, compared to about 7% for a stimulated IUI cycle and 3.5% for an unstimulated one. When researchers modeled the cost per live birth across both treatments, the numbers were closer than you might expect: about £12,600 for IVF versus £13,100 for unstimulated IUI followed by IVF if needed. The reason: IUI’s lower per-cycle cost is offset by needing more attempts, and many people still end up moving to IVF anyway.
That said, IUI’s lower upfront cost, minimal physical demands, and lack of surgical procedures make it a reasonable first step for many people, particularly those with unexplained infertility or mild male factor issues.
Risk of Multiples
The biggest risk specific to IUI is multiple pregnancy, especially when fertility medications are involved. The rate of twins and higher-order multiples from stimulated cycles is over 20 times greater than in natural conception.
The risk scales directly with the number of mature follicles present at the time of insemination. For women under 38, having just one mature follicle gives a multiple pregnancy rate of about 0.6% per cycle. With three or more follicles, over one quarter of all resulting pregnancies are multiples. At five mature follicles, the twin risk per pregnancy jumps to 23%, and the triplet risk reaches about 10%.
For women aged 38 to 40, the risk is lower but still significant. Five mature follicles push the twin risk per pregnancy to about 21%. This is why doctors monitor follicle development closely during stimulated cycles and may cancel a cycle if too many follicles develop, particularly in younger patients.
What to Expect Cycle to Cycle
A typical IUI cycle runs about two to three weeks from the start of medication to insemination. You’ll have several monitoring appointments during that time for blood draws and ultrasounds to track follicle growth. The insemination itself requires one clinic visit that’s usually over in under 30 minutes, including prep time. You can return to normal activities the same day.
About two weeks after insemination, you’ll take a pregnancy test. If the cycle doesn’t work, most people begin a new cycle with their next period. Your doctor may adjust medications or timing between cycles based on how your body responded. If three to six cycles of IUI don’t result in pregnancy, the typical next step is a conversation about moving to IVF, which involves retrieving eggs and fertilizing them in a lab before transferring an embryo to the uterus.