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Summary of IUI’s Risks
An IUI cycle generally bears minimal-to-moderate risk with the most noteworthy concern being the risk associated with delivering twins, triplets, or more.
Infection from IUI
An IUI procedure involves passing a soft plastic catheter through the cervix (the entrance to the uterus) and into the uterus. The prepared sperm sample is then gently forced out of a syringe, through the catheter tube and into the uterus. This is generally associated with mild cramping, but little-to-no pain.
The greatest risk to the patient is the introduction of bacteria or a virus into the uterus which can cause an infection. This can occur in two ways:
In passing the catheter through the vagina, bacteria is picked up and introduced into the uterus
The semen specimen itself carries an infectious agent
According to the best study in the field, over an 18 year period during which 48,000 inseminations with donor sperm were performed, 47 infections were reported culminating in an infection rate of less than 1 per 10,000 IUI cycles.
Twins, Triplets, Or More From IUI
Pregnancies of multiples are the most common and the most severe risk associated with IUI. When IUI is accompanied by clomid or letrozole, 1 - 14% of pregnancies involve multiple gestations. IUI accompanied by gonadotropin records even higher rates. Contrast this to IVF, where the rates can be as low as 1%, or as high as 30%, depending upon how many embryos you and the doctor choose to transfer at any one time.
While most twin pregnancies end with a positive outcome, multiples are associated with an increased risk of nearly all obstetric and neonatal complications.
Fetal Death and Other Complications
There is data to suggest the odds of complications from fertility treatment is not uniform across racial and ethnic populations. While disparities exist when people conceive without treatment, they seemingly become more pronounced with treatment.
For instance, one well-regarded study in Pediatrics suggests that compared with Caucasian patients, those of Black, Asian (broadly defined) and Latinx heritage record higher rates of fetal death or preterm delivery. However, it’s important to keep in mind these issues occur in the low single digit percentages of all deliveries.
That’s true amongst patients who conceived with oral medication for ovulation induction and IUI—as you can see from the data below.
It’s also true amongst patients who conceived using in vitro fertilization, often at levels comparable to oral medication and IUI.
Ovarian Hyperstimulation Syndrome (OHSS) & IUI
OHSS is a syndrome that occurs when the signal to the ovaries to recruit follicles becomes too strong. This results in swelling of the ovaries, abdominal bloating, leakage of fluid into the abdomen, and dehydration. This typically only occurs when high levels of gonadotropins are taken (like in an IVF cycle). However, this can occur in an IUI cycle if enough follicles are recruited, regardless of the medication taken.
The risk of OHSS in an IUI cycle when gonadotropins are used has been reported to be approximately 1%. However, three points warrant mentioning:
Most of the studies included to calculate this number used a high dose of gonadotropins (150 IU) and a higher dose of trigger medications than is typically used today (10,000 IU versus 5,000 IU)
If the patient is fearful they will develop OHSS, they can always cancel the cycle by not triggering ovulation
When clomid or letrozole are used prior to IUI the risk is nearly non-existent
Mood Swings and Hot Flashes With IUI
These side effects occur more often for IUI patients taking clomid or letrozole and less so for women taking gonadotropins.
In one study, nearly two-thirds of women reported some change in mood while on clomid. This typically means irritability (a “short fuse”), feeling down, and generalized discomfort due to bloating.
Hot flashes are the next most common side effect, occurring in up to a third of women taking clomid and 20% taking letrozole. These symptoms appear to be more common when higher doses (150 mg) of clomid are needed to cause ovulation.
Visual disturbances, manifesting as as shimmering sensation, sensitivity to light, and double vision, occur in about 2% of patients taking clomid or letrozole. If you experience these symptoms, you should report them to your doctor. Most of the time, these resolve without any issues. However, there have been extremely rare reports of longer term neurologic issues, so your doctor will probably change you to a different medication if you are experiencing these symptoms.
Pro Tips
The chief concern with IUI is the risk of multiples, which looks high on a per-pregnancy basis (8 - 30%), but since so few IUI’s result in pregnancy, the per-cycle risk is 0.5 - 2.5%. Multiple births are dangerous for both mother and offspring
Infection risk resulting from the insemination itself is 1 in 10,000
Risk of OHSS is likely less than 1%, typically happening only in gonadotropin cycles and can be avoided
Mood swings and hot flashes are especially customary to IUI when accompanied by clomid