In this phase of IVF, medication to stimulate the growth of the ovarian follicles is used. This medication is completely natural. These are the same substances (FSH, LH) which are produced by the pituitary gland to stimulate the follicles. Follicles are a type of small cysts which are formed in the ovaries, in which we find the egg cell. The aim of this treatment is obtaining these egg cells and take them out of the woman’s body. This medication is applied through subcutaneous injection. These are injections, but so simple and not painful at all, that they can be administered without any risks after a short course.
During a normal ovulation cycle, the ovaries produce just one follicle, and therefore, just one egg cell. If the ovaries would not be stimulated, we would only obtain one egg cell to be fertilised in each cycle, which would lower the chances of pregnancy substantially.
In the beginning, IVF was executed in a natural cycle. Afterwards, when the ovary stimulating hormones were discovered, hyperstimulation was applied.
Ovarian hyperstimulation commences when a woman has her period. On the second or third day, an ultrasound is done (and sometimes a blood test to check on some hormone levels such as LH). If the ovaries are resting, we start to inject the medication. On the fourth or the fifth day, the first ultrasound is done to check how the ovaries are responding.
The development of the hyperstimulation is followed through these ultrasound checks. The number of follicles is counted and their sizes are measured. This way, the doses of medication for the following days are adjusted. From here, there are checks every 2 to 3 days. At times it is also necessary to do a blood test to check on the hormone levels (LH).
Ovarian hyperstimulation in IVF normally takes approximately 9 to 10 days, until the main follicles reach a size of more than 18 mm. When this is the case, another type of medication will be injected (hCG), to complete maturation of the egg cell inside the follicles. And then everything is ready for the next phase (ovarian puncture, or oocyte retrieval).