The overall success rate of intrauterine insemination (IUI) is about 10 to 20 percent per cycle, with an average live birth rate around 13 percent. That number shifts considerably depending on your age, what’s causing the infertility, whether you use fertility medications, and sperm quality. Most people don’t conceive on the first try, and understanding what realistic expectations look like across multiple cycles can help you decide whether IUI is the right path or when it makes sense to consider other options.
How Age Affects IUI Success
Age is the single biggest factor in whether IUI works. A large study published in Fertility and Sterility tracked over 1,100 IUI cycles and found an overall pregnancy rate of 19.4 percent per cycle across all ages, with a live birth rate of 12.9 percent. For women aged 40 to 42, the live birth rate dropped to 9.8 percent per cycle.
A separate study of more than 2,700 IUI cycles among women aged 38 to 44 gives a clearer picture of how quickly the numbers decline in this age range:
- Age 38: 9.7% live birth rate per cycle
- Age 39: 7.8%
- Age 40: 10.1%
- Age 41: 7.7%
- Age 42: 5.7%
- Age 43: 3.5%
- Age 44: 3.0%
Women under 35 generally see the highest per-cycle success rates, typically in the range of 15 to 20 percent. After 35, egg quality and quantity begin to decline more rapidly, and by the early 40s the odds per cycle become quite low.
Success Rates by Diagnosis
The reason you’re having trouble conceiving plays a major role in how well IUI works. For unexplained infertility, one of the most common diagnoses, success rates run about 7 to 10 percent per cycle. After three medicated cycles using Letrozole or Clomid, cumulative success rates reach 15 to 25 percent.
For women with PCOS (polycystic ovary syndrome), IUI can work well, but only if ovulation actually occurs. PCOS often disrupts or prevents ovulation entirely, so the procedure is almost always paired with ovulation-inducing medication. Combining IUI with Clomid or Letrozole offers a modest boost in conception rates, and for women who need stronger medications called gonadotropins, IUI has been shown to significantly improve the chances of getting pregnant.
Male factor infertility is another common reason couples pursue IUI. The procedure bypasses several natural barriers by placing washed, concentrated sperm directly into the uterus. How well this works depends largely on sperm quality, which is covered in detail below.
Natural Cycle vs. Medicated IUI
Fertility medications meaningfully improve IUI outcomes. A large study of over 14,500 IUI cycles in couples with unexplained infertility found that natural-cycle IUI (no medications) produced a live birth rate of 6.2 percent per cycle. Adding medication increased that number:
- Clomid with IUI: 8.9% live birth rate
- Letrozole with IUI: 9.4% live birth rate
- Gonadotropins (injectable hormones) with IUI: 9.5% live birth rate
All three medication options performed about 50 percent better than a natural cycle. The differences between the medications themselves were small, though Letrozole carries a lower risk of multiple pregnancy, which is one reason many clinics now prefer it as a first-line option.
The Multiple Pregnancy Tradeoff
Fertility medications increase your chances of conceiving, but they also raise the odds of twins or higher-order multiples because they can cause more than one egg to mature and release. This is one of the most important risks to understand with medicated IUI.
Among women who became pregnant through IUI using Clomid, about 20 percent of those pregnancies were multiples. With Letrozole, that rate was lower at roughly 12.5 percent. In women with ovulatory dysfunction specifically, Letrozole cut the multiple pregnancy rate significantly: 6.5 percent versus 15.6 percent with Clomid.
Dosing matters too. Increasing the Clomid dose from 50 mg to 100 mg actually decreased the pregnancy rate (from 18.2 to 16.3 percent) while increasing the multiple pregnancy rate (from 19.8 to 25.7 percent). Similarly, bumping Letrozole from 2.5 mg to 5 mg didn’t improve pregnancy odds but did increase multiples from 7.7 to 22.8 percent. Higher doses are not always better, and your clinic will try to find the minimum effective dose.
How Sperm Quality Changes the Odds
The total motile sperm count after the sperm sample is washed and prepared is a key predictor of IUI success. Most fertility specialists recommend a post-wash count of at least 5 to 10 million progressively motile sperm for a reasonable chance of success. Below that range, pregnancy rates drop significantly.
That said, the picture is more nuanced than a hard cutoff. Research published in Fertility and Sterility found that pregnancy rates were comparable whether the post-wash count was 2 to 5 million or above 5 million, particularly when the female partner was under 35. The real drop-off came below 1 million motile sperm, where pregnancy rates declined sharply. If sperm counts consistently fall below these thresholds, your clinic will likely recommend IVF with a specialized fertilization technique instead.
Timing the Procedure
IUI is typically performed after a trigger shot of hCG, a hormone that causes the mature egg to release from the ovary. The timing between the trigger shot and the insemination can influence success. Most clinics schedule IUI about 36 hours after the trigger, but a randomized study found that waiting 48 hours produced a significantly higher pregnancy rate: 22.6 percent compared to 10.6 percent at 36 hours.
This is a single study, and practices vary between clinics. Some perform two inseminations per cycle, spacing them 24 hours apart to cover a wider window. The key takeaway is that precise timing relative to ovulation matters, which is why clinics use ultrasound monitoring and hormone blood tests to pinpoint when you’re most fertile.
IUI Compared to IVF
For women under 35 with a good prognosis, IUI is a reasonable and far less expensive first step. But the gap between IUI and IVF widens as age increases. Among women 38 to 44, IVF produces pregnancy and live birth rates roughly 2.5 times higher than IUI. The breakdown by age makes the difference clear:
- Age 38: IVF 27.8% vs. IUI 9.7%
- Age 40: IVF 19.2% vs. IUI 10.1%
- Age 42: IVF 10.4% vs. IUI 5.7%
- Age 44: IVF 3.2% vs. IUI 3.0%
By age 44, the two approaches produce nearly identical results, both quite low. For women in their late 30s and early 40s, three to four failed IUI cycles is often the point at which clinics recommend transitioning to IVF. Each unsuccessful IUI cycle costs time, and for older patients, time translates directly into declining egg quality.
Cumulative Success Over Multiple Cycles
Because per-cycle rates are modest, most people need more than one attempt. The standard recommendation is three to four medicated IUI cycles before reassessing. For unexplained infertility, cumulative success across three medicated cycles reaches roughly 15 to 25 percent. After three to four failed cycles, the incremental benefit of additional IUI attempts drops substantially, and most of the couples who will conceive through IUI have done so by that point.
Your individual odds depend on the combination of all the factors discussed here: age, diagnosis, sperm quality, medication protocol, and timing. A 30-year-old with unexplained infertility, good sperm parameters, and a medicated cycle sits at the higher end of the range. A 41-year-old with diminished ovarian reserve sits at the lower end. Understanding where you fall on that spectrum helps set expectations and informs whether IUI is a sensible starting point or whether moving directly to IVF will save time and emotional energy.