When should myo‑inositol supplementation be stopped relative to the hCG (or GnRH‑agonist) trigger and egg retrieval in an IVF cycle?

When to Stop Myo-Inositol Before Egg Retrieval

Continue myo-inositol supplementation throughout the entire ovarian stimulation period and stop it on the day of the hCG (or GnRH-agonist) trigger injection, approximately 35-37 hours before oocyte retrieval.

Evidence-Based Timing Protocol

The available research demonstrates that myo-inositol should be administered continuously during the stimulation phase to optimize outcomes:

• Pre-treatment phase: Administer myo-inositol 2g twice daily (combined with 200 mcg folic acid) for 3 months before starting ovarian stimulation to improve insulin sensitivity, reduce androgen levels, and enhance oocyte quality 1, 2, 3.

• During stimulation: Continue myo-inositol throughout the entire gonadotropin stimulation period (typically 10-14 days), as this is when it exerts its beneficial effects as a second messenger of FSH and facilitates glucose transport into developing follicles 1, 2.

• Discontinuation timing: Stop myo-inositol on the day of trigger injection (when follicles reach ≥17-18mm diameter), which occurs 35-37 hours before scheduled oocyte retrieval 4, 5.

Rationale for This Timing

The mechanism of action supports continuation through stimulation:

• Myo-inositol functions as a second messenger for FSH signaling, directly supporting follicular development and oocyte maturation throughout the stimulation phase 1.

• Studies demonstrating benefit used protocols where myo-inositol was continued "during the stimulation itself" and "through treatment," indicating it should not be stopped prematurely 2, 3.

• The trigger injection (hCG or GnRH-agonist) initiates final oocyte maturation over 35-40 hours, after which the oocytes are retrieved—at this point, myo-inositol's role in FSH signaling is complete 4, 5.

Expected Benefits When Used Correctly

When myo-inositol is continued appropriately through stimulation:

• Reduced gonadotropin requirements: Significantly lower total rFSH doses needed to achieve follicular maturation 2.

• Improved oocyte quality: Greater number of mature oocytes (>15mm follicles), higher-quality embryos (improved embryo scores), and reduced immature/degenerated oocytes 3.

• Better pregnancy outcomes: Maintained or improved clinical pregnancy and implantation rates despite using less gonadotropin 1, 2.

Common Pitfalls to Avoid

• Do not stop myo-inositol early in the stimulation cycle: The benefits on oocyte quality and FSH response require continuous supplementation throughout the entire stimulation period 2, 3.

• Do not continue after trigger: There is no evidence supporting continuation beyond the trigger injection, and doing so provides no additional benefit once final oocyte maturation has been initiated 5.

• Do not use myo-inositol as a substitute for evidence-based protocols: While myo-inositol is a useful adjunct, it does not replace appropriate monitoring (transvaginal ultrasound every 2-3 days plus estradiol levels) or proper trigger timing when ≥3 follicles reach ≥17mm 4.

Special Considerations

For patients with specific medical conditions requiring anticoagulation during ART (such as antiphospholipid syndrome):

• Low-dose aspirin should be stopped 3 days before egg retrieval and resumed the following day 6.

• LMWH should be stopped 12-24 hours prior to retrieval and resumed the same day if no bleeding 6.

• These anticoagulation timing protocols are independent of myo-inositol discontinuation 6.