Normally, each month there are about 25 follicles (in which eggs grow) prepared in the ovary, but only one egg matures and is released. For the IVF method it is necessary that a higher amount of eggs is prepared in the ovaries an therefore, so-called ovarian stimulation is induced by hormonal medication.
A higher amount of follicles (cavities growing in the ovaries) develop after appllication of the hormones (gonadtropins).
The growing follicle produces estrogen, which triggers the rise of a luteinizing hormone (LH). In a natural cycle it allows the release of mature eggs from the ovary. During the stimulation, a fertility drug, that delays natural ovulation and prevents a premature LH rise, is applied.
Ovulation (egg maturation) is induced by injected chorionic gonadotropin (hCG), which must be applied about 32-36 hours before the scheduled egg retrieval.
On the one hand, it is about getting an appropriate number of eggs, on the other hand, trying to avoid excessive reaction (hyperreaction)
The examinations (even repeated) do not have any side effects on eggs or embryos in the early stages of pregnancy.