A number of fertility problems can be remedied in whole or in part by hormonal stimulation of the woman's cycle. This hormonal stimulation may be indicated in women with cycle disorders (such as no ovulation or a very irregular cycle), or with ferility disorders without any obvious cause.
The doctor may be attempting to achieve a number of aims with hormonal treatment:
- Ovulation: hormonal stimulation can ensure that at least one ovum matures per cycle.
- A monitored, regular cycle: careful stimulation with the aim of causing one or two ova to mature and stimulating ovulation, either in combination with sperm cell insemination or not.
- With IVF or ICSI: super-ovulation: ovulation whereby not one but eight, ten, twelve or more ova mature simultaneously. This can increase the chance of success with in vitro and injection treatments.
When several ova mature simultaneously and fertilisation occurs after spontaneous sexual intercourse or after insemination with sperm cells, this implies the risk of a multiple pregnancy. With careful monitoring and follow-up during the hormonal stimulation the number can virtually always be limited to twins or at the most triplets. Thanks to improvements in the assistance provided multiple births involving more than three babies have become a rarity in Belgium.
A second risk of hormonal stimulation is ovarian hyperstimulation syndrome (OHSS). OHSS occurs in sensitive patients, but unfortunately is also sometimes due to careless stimulation with an overly high dose of hormones. This causes the ovaries to swell badly and cysts measuring 20 to 30 mm in diameter may form. This can usually be avoided by using a sufficiently low dose and by means of good follow-up during the stimulation. Nevertheless, sensitive patients (such as those with polycystic ovaries) may react too strongly even under these circumstances. If this situation is observed in time, an attempt can be made to avoid the hyperstimulation syndrome by stopping the treatment, removing a number of follicles using ultrasound or by switching to ovum aspiration and in vitro fertilisation, possibly freezing the fertilised ova with a view to replacing them in the uterus at a later date (during a thawing cycle).