IUI (Intrauterine Insemination): What to Expect

How does IUI work?

During natural conception, sperm must travel through the vagina, past the cervix, through the uterus, and into a fallopian tube to meet an egg. The cervix filters and slows sperm; IUI bypasses that barrier by placing sperm directly into the uterine cavity.

The sperm sample is first "washed" in the laboratory — a process that separates motile (moving) sperm from seminal fluid, dead sperm, and other cellular material. Seminal fluid contains prostaglandins that can cause uterine cramping if introduced directly; washing both concentrates the best sperm and makes the procedure more comfortable.

The washed sperm is then loaded into a thin, soft catheter and inserted through the cervix into the uterus. The timing is synchronized with ovulation — the window when an egg is released and fertilizable — to maximize the chance of sperm meeting the egg 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2020).Evidence-based treatments for couples with unexplained infertility: a guideline.IUI as first-line treatment for unexplained infertility; indications and appropriate patient selection for IUI vs. IVF; timing and use of ovarian stimulation with IUI.

Who is IUI typically used for?

IUI is a reasonable first-line treatment in several situations:

• Unexplained infertility — no clear cause identified after evaluation; IUI with ovarian stimulation is an established approach 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2020).Evidence-based treatments for couples with unexplained infertility: a guideline.IUI as first-line treatment for unexplained infertility; indications and appropriate patient selection for IUI vs. IVF; timing and use of ovarian stimulation with IUI
• Mild male factor infertility — moderately reduced sperm count or motility; the male fertility evaluation helps guide whether IUI or IVF is more appropriate 2Ref 2Brannigan RE, Hermanson L, Kaczmarek J, et al. (2024).Updates to Male Infertility: AUA/ASRM Guideline (2024).Evaluation and management of male factor infertility; guidance on when post-wash sperm parameters indicate IUI is appropriate vs. proceeding to IVF with ICSI
• Cervical factor — cervical mucus abnormalities that may impair sperm transport
• Sexual dysfunction — conditions that make timed intercourse difficult
• Use of donor sperm — including single individuals and same-sex couples

IUI is generally less appropriate when fallopian tubes are blocked (since sperm still needs to travel through the tube to reach the egg), when male factor infertility is severe (particularly very low post-wash sperm counts), or when ovarian reserve is very diminished. A reproductive endocrinologist will assess whether IUI or IVF is the better path based on the specific diagnosis 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2020).Evidence-based treatments for couples with unexplained infertility: a guideline.IUI as first-line treatment for unexplained infertility; indications and appropriate patient selection for IUI vs. IVF; timing and use of ovarian stimulation with IUI.

What happens in the lead-up to IUI?

Monitoring cycles IUI can be done in a natural (unmedicated) cycle, where ovulation is tracked with urine LH strips or ultrasound, or in a stimulated cycle, where low-dose fertility medications (typically oral agents or injectable gonadotropins) are used to recruit one or two follicles and improve timing precision.

Stimulated IUI cycles typically involve: 1. Starting medication on a specified cycle day 2. Ultrasound monitoring visits (usually 2–3) to check follicle development and uterine lining 3. A trigger shot (hCG or similar medication) once a mature follicle is seen, to time ovulation precisely 4. The IUI procedure scheduled 24–36 hours after the trigger

Semen sample The sperm sample is collected by the partner or donor on the day of the procedure (usually via masturbation at the clinic or at home within a specific time window), or thawed from frozen donor samples. The lab processes it before the procedure.

What happens on the day of the procedure?

The IUI procedure itself is brief:

1. You lie on the exam table as you would for a pelvic exam 2. A speculum is placed to visualize the cervix 3. The catheter with washed sperm is gently guided through the cervical opening into the uterine cavity 4. The sperm is slowly released 5. The catheter is removed

The whole procedure typically takes 5–15 minutes from start to finish. Most people experience mild cramping — similar to menstrual cramps — during or briefly after the catheter passes through the cervix. A small number of people have more significant cramping.

You will usually be asked to rest for a few minutes afterward, but you can typically return to normal activities the same day. There is no evidence that bed rest after IUI improves outcomes.

What should I expect after IUI?

After IUI:

• Spotting — light spotting from catheter placement is normal and does not affect outcomes
• Cramping — may continue mildly for several hours; over-the-counter pain relief is usually adequate if needed
• The two-week wait — pregnancy testing is typically done approximately 14 days after the procedure, once hCG (whether from a trigger shot or early pregnancy) has cleared
• Progesterone support — some clinics prescribe progesterone supplementation after IUI to support the uterine lining during the potential implantation window; practice varies by clinic and individual situation

Gale can help you prepare for a consultation with a reproductive endocrinologist if you are considering IUI.