Preventing a premature rise in luteinizing hormone (LH) is essential during ovarian stimulation for in vitro fertilization (IVF), because such a rise can reduce the number of eggs collected. Current practice relies on either a daily injectable GnRH antagonist or an oral progestin (PPOS), which requires that all embryos be frozen.

Linzagolix is an oral GnRH antagonist already approved for uterine fibroids and endometriosis. It has not previously been used to control ovarian stimulation for IVF; this study represents its first use for this purpose.

This is an observational study: participants are not randomly assigned to a treatment. Each woman receives one of three approaches - oral linzagolix, an injectable GnRH antagonist (ganirelix or cetrorelix), or PPOS - chosen by the clinical team based on her individual situation. The three groups are then compared using statistical adjustment for baseline differences between them.

The study will enroll approximately 195 women undergoing IVF or ICSI, aged 18 to [42], who are not selected based on ovarian reserve. All participants receive individualized gonadotropin stimulation and standard monitoring; only the method used to prevent premature ovulation differs by group.

The main question is whether linzagolix leads to a similar number of mature eggs (MII) retrieved compared with the injectable antagonist. The study will also assess how well each approach suppresses LH, safety (including ovarian hyperstimulation), and the number of injections needed.