IVF Trigger Shots and Luteal Phase Support – The Final Steps Before Pregnancy

Once the follicles have matured during stimulation, the next two steps are crucial for a successful IVF outcome: (1) triggering final oocyte maturation, and (2) supporting the uterine lining for implantation. Each stage involves carefully chosen medications that optimize success and reduce risk.

🔹 Trigger Injections – Signaling the Final Egg Maturation

The trigger shot mimics the body’s natural LH surge, signaling the final phase of egg development and preparing for retrieval ~36 hours later.

✅ Common Trigger Medications:

Medication Type Usage Notes hCG (human chorionic gonadotropin)Traditional trigger Pregnyl®, Novarel® (urinary); Ovidrel® (recombinant). Mimics LH, time-tested. GnRH Agonist (e.g., Lupron®)Modern trigger Causes the pituitary to release endogenous LH and FSH surge. Often used in antagonist protocols. Dual Trigger Combo of hCG + GnRH agonist Used in high responders or previous failed cycles to improve egg maturation while reducing OHSS risk.

⚠️ Important Considerations:

• OHSS (Ovarian Hyperstimulation Syndrome): hCG increases OHSS risk in high responders (e.g., PCOS patients). A GnRH agonist is safer in these cases.

• Trigger timing is critical — retrieval must occur ~36 hours after injection to avoid ovulation in vivo.

🔹 Luteal Phase Support – Holding the Uterine Lining

After the egg retrieval, the ovaries are no longer producing hormones at natural levels due to follicle aspiration. Luteal support replaces these missing signals to maintain a receptive endometrium for embryo transfer.

✅ Common Medications for Luteal Support:

Medication Route Brand Examples Notes Progesterone in Oil (PIO)Intramuscular Generic Gold standard; reliable absorption, but painful and inconvenient. Micronized Vaginal Progesterone Vaginal Endometrin®, Crinone® Less invasive; used widely in Europe and in some U.S. clinics. Oral Progesterone Oral Prometrium® Less commonly used due to inconsistent serum levels .Estradiol (E2)Oral or patch Estrace®, Vivelle-Dot® Used when estrogen support is needed alongside progesterone.

🔬 Protocol Duration:

• Usually continues until the 10th–12th week of pregnancy, or until the placenta begins producing its own progesterone and estrogen (placental takeover).

• Some clinics stop earlier if a natural LH surge occurred (e.g., in modified natural cycles).

🧬 Personalized Approaches

Luteal support is tailored based on:

• Type of stimulation and trigger

• Fresh vs. frozen transfer

• Patient’s hormone levels

• Clinic preference and evidence-based trends

Recent studies are also exploring subcutaneous progesterone, progesterone serum monitoring, and timed cessation based on early hCG rise.

✅ Summary

Phase Medications Purpose Trigger hCG, GnRH agonist, or both Induce final egg maturation Luteal Support Progesterone (IM, vaginal, or oral), Estradiol Maintain endometrial receptivity post-transfer