In an IVF cycle, what is the purpose of the human chorionic gonadotropin (hCG) trigger?

• A. To stimulate endometrial lining.
• B. To prevent luteal phase dysfunction.
• C. To mature oocytes and induce final maturation before retrieval.
• D. To cause ovulation in natural cycles.

Answer: (C)

The main idea is to mimic the natural LH surge so the eggs finish maturing at the right time. Administering hCG acts like LH, triggering final oocyte maturation and resumption of meiosis, so the eggs reach the metaphase II stage and are ready for retrieval. In an IVF cycle, the oocytes are collected about 34–36 hours after the hCG shot, which timing relies on this maturation signal. It also helps ensure the follicles can release the oocytes at the planned time, rather than ovulating prematurely.

This isn’t about building the endometrial lining, which is governed by estrogen and progesterone in separate steps, nor primarily about preventing luteal-phase dysfunction—luteal support is provided after retrieval if needed. And while hCG does have luteotrophic effects, its principal purpose in IVF triggers is to induce final oocyte maturation and to allow precise timing of egg retrieval, not to induce ovulation in a natural cycle.