Intrauterine insemination (IUI) is a fertility treatment where specially prepared sperm is placed directly into the uterus around the time of ovulation. It’s one of the simplest and least expensive assisted reproduction options, with per-cycle pregnancy rates ranging from about 9% to 13% for most adults under 40. IUI is often the first treatment doctors recommend before considering more advanced options like IVF.
How IUI Works
During natural conception, sperm must travel from the vagina through the cervix and into the uterus to reach the fallopian tubes, where fertilization happens. A large percentage of sperm never make it past the cervix. IUI shortens that journey by placing a concentrated sample of healthy sperm directly into the uterus through a thin, flexible catheter. This increases the number of sperm available to meet the egg.
The procedure itself takes only a few minutes. You lie on an exam table, and the doctor inserts the catheter through the cervix. Most people describe it as feeling similar to a Pap smear. There’s no anesthesia, no incision, and you can typically go back to your normal routine the same day.
Why the Sperm Gets “Washed” First
Before insemination, the sperm sample goes through a preparation process called washing. This separates the healthiest, most active sperm from the rest of the semen. The washing step also removes white blood cells, bacteria, dead sperm, and other debris that produce harmful molecules capable of damaging healthy sperm and reducing their ability to fertilize an egg.
Skipping this step isn’t just less effective, it’s risky. Placing unprepared semen directly into the uterus can cause severe cramping, uterine infection, and inflammation. Research has also linked it to higher rates of miscarriage and premature delivery. The washing process concentrates the best sperm into a small, potent sample, which is a key reason IUI works better than simply timing intercourse for many couples.
Who Is a Good Candidate
IUI is commonly recommended for several types of fertility challenges. The most frequent reasons include:
- Unexplained infertility: When standard testing hasn’t identified a clear cause after at least a year of trying
- Mild male factor infertility: Lower-than-average sperm count or motility, as long as the post-wash count is above about 5 million sperm
- Ovulation disorders: Including polycystic ovary syndrome (PCOS) and other conditions where ovulation is irregular or absent
- Mild endometriosis: Minimal to mild stages of the condition
- Cervical issues: When the cervix creates a barrier to sperm reaching the uterus
- Use of donor sperm: For single parents or same-sex couples
IUI is not a fit for everyone. If both fallopian tubes are blocked, you have moderate to severe endometriosis, or the sperm count after washing falls below about 1 million per milliliter, IVF is typically the better path.
Medicated vs. Natural Cycles
IUI can be done during a natural menstrual cycle with no fertility drugs, but it’s more commonly paired with medication to stimulate the ovaries and improve the chances of success. There are two main approaches to medication.
Oral medications like clomiphene or letrozole are the most common starting point. These are typically taken for five days early in the menstrual cycle, starting around day three to five, and they encourage the ovaries to develop one or more mature eggs. Injectable hormones (gonadotropins) are sometimes added or used on their own for a stronger response. The trade-off with more aggressive medication is a higher risk of multiple pregnancy.
Throughout a medicated cycle, your doctor monitors follicle growth with ultrasound. When the lead follicle reaches about 17 to 18 millimeters, a “trigger shot” of hCG is given to prompt ovulation on a predictable schedule. The insemination is then performed roughly 36 to 38 hours later, placing the sperm in the uterus one to two days before ovulation, which is the ideal window.
Success Rates by Age
Age is the single biggest factor affecting IUI success. An analysis of over 4,200 IUI cycles found clear differences across age groups. Per individual cycle, pregnancy rates were about 13% for women ages 25 to 29, around 11% for ages 30 to 34, and roughly 9% for ages 35 to 41. After 42, rates drop to about 6% per cycle, and beyond 43 they fall to around 3.5%.
Those numbers can feel discouraging, but they represent a single attempt. Over multiple cycles, cumulative odds improve. The overall pregnancy rate per patient (across an average of about two to two and a half cycles) was 26% to 28% for women under 35, about 22% for ages 35 to 39, and around 15% for ages 42 to 43. Notably, women aged 40 and 41 had success rates within the first three cycles that were comparable to those of women in their late 30s.
How Many Cycles to Try
Most fertility specialists recommend three to four IUI cycles before discussing IVF. If pregnancy hasn’t occurred after that point, the likelihood that additional IUI cycles will work drops considerably, and the emotional and financial toll adds up. For women over 40, many clinics recommend fewer IUI attempts, sometimes just one or two, before moving to IVF, since the per-cycle success rate is lower and time matters more.
The Risk of Multiples
The most significant risk of medicated IUI is multiple pregnancy. When fertility drugs stimulate the ovaries, more than one egg may be released, and there’s no way to control how many get fertilized once sperm is placed in the uterus. Among IUI pregnancies that used injectable hormones and resulted in a live birth, one study found that about 18% were twins, 7% were triplets, and 4% were quadruplets. The overall rate of high-order multiples (triplets or more) across multiple studies ranges from 7% to nearly 12%.
Multiple pregnancies carry real health risks for both the parent and babies, including preterm birth, low birth weight, and pregnancy complications. This is why careful ultrasound monitoring matters. If too many follicles develop during a medicated cycle, your doctor may recommend canceling the cycle or converting to IVF, where the number of embryos transferred can be controlled.
What It Costs
IUI is significantly cheaper than IVF. The procedure itself ranges from about $250 to $4,000 per cycle depending on your clinic and location. Oral fertility medications add $10 to $100 per month. If injectable hormones are part of your protocol, expect an additional $1,000 to $3,500 per cycle for those drugs. Donor sperm, if needed, runs $25 to $1,500 per vial. Insurance coverage varies widely, so check whether your plan includes fertility treatment before starting.