What are the guidelines for a 20-45 year old patient with a body mass index (BMI) between 18.5 and 30 undergoing Intrauterine Insemination (IUI)?

Intrauterine Insemination (IUI) Guidelines for Patients Age 20-45 with BMI 18.5-30

For patients in this age and BMI range undergoing IUI, perform single insemination 24-40 hours after hCG trigger when 1-2 follicles reach 16-18mm, use low-dose ovarian stimulation (≤75 IU gonadotropins daily or clomiphene citrate), ensure total motile sperm count >10 million, and complete at least 3 cycles before transitioning to IVF. 1, 2, 3, 4

Patient Selection Criteria

Mandatory prerequisites before proceeding with IUI include:

• At least one patent fallopian tube confirmed 4, 5
• Total motile sperm count (TMSC) >10 million for optimal outcomes with ovarian stimulation 4, 5
• TMSC between 3-10 million acceptable for natural cycle IUI, though outcomes are less favorable 4
• Post-wash inseminating motile count >0.8-5 million 4
• Sperm morphology >4% normal forms 4
• Infectious disease screening completed per WHO standards for both partners 4

Your BMI range (18.5-30) is optimal for IUI, as higher BMI (≥25) has been associated with improved pregnancy rates in some studies, likely due to thicker endometrial development. 6, 7

Ovarian Stimulation Protocol

Use low-dose gonadotropins (≤75 IU/day), clomiphene citrate, or tamoxifen for ovarian stimulation. 2, 4, 5 This is critical because:

• Higher gonadotropin doses increase multiple pregnancy rates without improving overall pregnancy rates 4
• Natural cycle IUI shows no benefit over timed intercourse in unexplained infertility 4
• Controlled ovarian stimulation significantly improves pregnancy outcomes compared to natural cycles 5

Do NOT use GnRH agonists or antagonists in IUI cycles—international guidelines explicitly recommend against this due to lack of pregnancy rate improvement despite increased costs and multiple pregnancy risk. 2

Trigger Timing and Follicle Development

Administer hCG trigger (5,000 IU IM or subcutaneous) when:

• 1-2 follicles measure 16-18mm or larger (>15mm minimum) 2, 3, 4
• AND <5 follicles measure >10mm 2, 3

Mandatory cycle cancellation criteria to prevent high-order multiple pregnancies:

• 2 follicles >15mm (multiple pregnancy risk jumps to 14-23%) 2, 3

• OR >5 follicles >10mm (unacceptable high-order multiple risk) 2, 3
• Alternative: aspirate excess follicles or convert to IVF 2

The evidence shows pregnancy rates improve with 2 mature follicles versus 1 (5% increase), but risk escalates dramatically beyond this: 6% multiple pregnancy risk with 2 follicles, 14% with 3 follicles, and 10% with 4 follicles. 3

Insemination Procedure

Perform single IUI 24-40 hours after hCG trigger (or 1 day after spontaneous LH surge detection). 1, 2, 3

• Double insemination within the same cycle provides no benefit and should not be performed 1, 3
• This applies to both unexplained and male factor infertility 1

Post-insemination bed rest: The evidence is mixed on this point. Two studies showed benefit from 10-15 minutes of immobilization (live birth rate 27% vs 17%), but the most recent large RCT (2017) found no significant difference. 1 Given the conflicting data and minimal burden, 10-15 minutes of bed rest is reasonable but not mandatory. 1

Treatment Duration

Complete at least 3 consecutive IUI cycles before transitioning to IVF/ICSI. 4 This represents the evidence-based threshold where IUI offers diminishing returns. Success rates plateau after 3-4 cycles in most studies. 5

Age-Specific Considerations for Your Range

Female age is the most relevant predictor of IUI success. 1 Within your 20-45 age range:

• Women <35 years have significantly better outcomes 1
• Women >35 years experience progressively lower success rates 1
• IUI has limited utility in advanced maternal age ≥35 years, particularly when combined with other factors 5

If you are approaching or over 35, consider more aggressive transition to IVF after 3 failed IUI cycles rather than extending IUI attempts. 1, 5

Common Pitfalls to Avoid

Do not proceed with IUI if:

• Fallopian tube sperm perfusion (FSP) is offered instead—it provides no benefit over standard IUI 1
• TMSC is consistently <3 million—this represents the lower threshold for IUI consideration 4
• Severe male factor, tubal factor, or severe endometriosis is present—these are poor IUI candidates 5

Do not delay IUI for minor systemic illnesses like upper respiratory infections—these are not contraindications and have no documented impact on success rates. 4 The infection rate from IUI itself is extremely low (0.183%). 4

Monitor endometrial thickness on trigger day—pregnancy rates increase significantly with thicker endometrium, and this factor may be underappreciated in IUI therapy. 8 Peak endometrial thickness declines with age and varies with estradiol levels. 8