Which IVF protocol to use?

Published: 05 January 2012

For IVF cycles, the most common in use today are the agonist or antagonist protocol...

Antagonist protocol

These types of drugs (such as Cetrotide or Orgalutran) prevent premature ovulation and are used for pituitary suppression. Antagonist means ‘to resist’ – these drugs take less time to suppress the pituitary gland. It may also give a better response for someone with a low ovarian reserve.

Agonist protocol

Agonist means ‘to create a response'. This is the classic IVF protocol for long down regulation. Day 21 involves the use of agonists to suppress the pituitary gland before starting stimulation. The drugs work by suppressing this gland and resolving any residual ovarian function from the previous cycle, i.e cysts.

Ten days minimum are needed to suppress the pituitary gland and down regulate – it is usually seven days before the next period when the suppression down regulation (blocking the pituitary) is commenced. This is done before starting stimulation of the ovaries – by desensitising the pituitary, it allows the recruitment of more than one follicle. If you do an ultrasound scan, you can see the potential follicles in the ovaries that might grow on the ultrasound scan – typically, one dominant follicle is selected each month and the others die off. Although women have the potential each month to produce more than one follicle, usually the pituitary gland stops more than one follicle developing each month, as nature’s way of preventing multiple pregnancies.

Allowing more follicles to grow by giving gonadotrophin hormones such as FSH follicle stimulating hormone, i.e. Gonal F, for the suppression of the pituitary, allows us to control when ovulation occurs by blocking the natural LH surge.