IUI vs IVF: How to Know When It's Time to Switch
IUI is simpler and cheaper. IVF is more effective and more invasive. The question isn't which is “better” — it's which is right for your specific situation, and when to move from one to the other.
IUI success rates are 10–20% per cycle. IVF is 40–60% per cycle (under 35). Most guidelines recommend switching after 3–4 failed IUI cycles, or sooner if specific conditions favor IVF from the start.
How IUI Works
Intrauterine insemination (IUI) places washed, concentrated sperm directly into the uterus around the time of ovulation. It skips the cervix, giving sperm a head start. The procedure itself takes about 5 minutes and feels similar to a Pap smear.
IUI is typically combined with ovulation induction medication — letrozole or clomiphene citrate — to ensure ovulation timing is predictable and to potentially produce 1–2 mature follicles rather than just one.
How IVF Works
In vitro fertilization involves stimulating the ovaries with injectable medications to produce multiple eggs, retrieving those eggs in a minor outpatient procedure, fertilizing them in the lab, and transferring the resulting embryo(s) to the uterus 3–6 days later.
IVF is more controlled, more predictable, and significantly more effective — but it's also more expensive, time-intensive, and physically demanding.
Head-to-Head Comparison
| Factor | IUI | IVF |
|---|---|---|
| Success rate (under 35) | 10–20% per cycle | 40–60% per cycle |
| Success rate (35–39) | 8–15% | 30–45% |
| Success rate (40+) | 2–5% | 15–25% (own eggs) |
| Cost per cycle (US) | $500–$4,000 | $12,000–$25,000 |
| Medications | Oral (+ optional trigger) | Daily injectables |
| Monitoring visits | 1–3 per cycle | 5–8 per cycle |
| Procedure invasiveness | Minimal | Egg retrieval under sedation |
| Time commitment | ~1 week active | ~2–3 weeks active |
| Genetic testing option | No | Yes (PGT-A) |
| Multiple pregnancy risk | Higher (uncontrolled) | Lower with eSET |
When IUI Makes Sense
Unexplained infertility (under 38): IUI with letrozole or clomid is a reasonable first step when no clear cause has been identified.
Mild male factor: If sperm count or motility is slightly below normal, IUI's sperm washing and direct placement can help.
Cervical factor: If cervical mucus is hostile to sperm or the cervix makes natural passage difficult.
Donor sperm: For single women or same-sex couples using donor sperm, IUI is often the first-line approach if the carrying partner has no fertility issues.
Cost constraints: When IVF isn't financially accessible yet, 2–3 IUI cycles at $500–$2,000 each can be a worthwhile attempt.
When to Skip IUI and Go Straight to IVF
Tubal factor: Blocked or damaged fallopian tubes. IUI requires functional tubes; IVF bypasses them entirely.
Severe male factor: Very low sperm count (under 5 million motile sperm after wash), poor morphology, or high DNA fragmentation. ICSI with IVF can work with even a single viable sperm.
Age over 38–40: With lower per-cycle odds, the cumulative time and cost of multiple IUI cycles may exceed the cost of proceeding directly to IVF with its higher success rates.
Diminished ovarian reserve: Low AMH or high FSH suggests fewer eggs, making IVF's controlled stimulation more efficient.
Endometriosis (moderate to severe): Stage III–IV endometriosis significantly reduces IUI effectiveness.
Desire for genetic testing: If you want PGT-A to screen embryos for chromosomal abnormalities, IVF is the only path.
The Switch Point: When IUI Should Become IVF
Most reproductive endocrinologists recommend transitioning to IVF after 3–4 failed IUI cycles. Here's the reasoning:
The cumulative success rate of IUI plateaus after 3–4 attempts. If IUI hasn't worked by then, additional cycles are unlikely to change the outcome. Studies show that 85–90% of IUI pregnancies occur within the first 3 cycles. Continuing beyond that has diminishing returns while delaying more effective treatment.
Three IUI cycles at 15% each give you a cumulative ~38% chance of pregnancy. One IVF cycle at 50% gives you a 50% chance. If the first IUI doesn't work, the decision framework should shift toward IVF efficiency rather than repeated IUI attempts.