Stimulation protocols  in IVF aim at ovarian stimulation in order to achieve maturation of many follicles and collection of  oocytes from each patient during each treatment cycle.

In the past, some medications were considered to cause ovarian and breast cancer. Up to this time there is no such scientific proof  to support this view.

A recent paper by Alan Trounson  from the University of Monash in Australia, who performed a follow up study of 10.358 women since 1978, reported no increase in breast or ovarian cancer after hormonal therapy and in vitro fertilization. Other reports coming from the U.K came to the  same conclusions.

Possible complications due to hormonal medications include allergic reactions, breast tenderness, body fluid increase as well as restlessness. The most severe complication is ovarian hyperstimulation (OHSS), which occurs in 3-5 % of patients.
 
Ovarian hyperstimulation is characterised by severe ovarian enlargement, fluid accumulation inside the abdominal and chest cavity, abdominal pain, vomiting and shortness of breath.

Treatment is based on medical therapy, and in severe cases admission to hospital may be needed.