Hello, and I hope I can help you today. Endometriosis is a disease that can be frequently associated with infertility, because it makes a woman bleed internally every time she has a menstrual cycle. This can cause scarring and inflammation which can cause pain for the woman and difficulties getting pregnant. So treatment for endometriosis is effective if it suppresses the woman s natural menstrual cycle. Decapeptyl is one type of medication used for this purpose. This treatment for endometriosis is actually supported by medical evidence. However, the reason why your doctor is prescribing this medication is to cause a drop in estrogen during the early part of your wife s menstrual cycle which theoretically would increase the chance of ovulation. This is not a medically supported dosing regimen, and there are other medications in pill form that can conceive the objective of increasing ovulation rates with less risk and side effects. So in summary, if the medication were prescribed to suppress your wife s menstrual cycles monthly for period of six months to help control her endometriosis that is an effective treatment. However the regimen your doctor is suggesting has not been proven to be effective for increasing fertility, and may produce unpleasant side effects. In addition there are other medications which are not injectable that can be tried first. So I hope I was able to adequately answer your question today, and that the information I gave you was helpful. I wish your wife the best of health and that you are able to conceive successfully, Sincerely, Dr. Brown