Male patients who are taking certain MPD medications need to be careful that their partner does not become pregnant. Drugs that do NOT cause a problem include aspirin, interferon alpha and anagrelide. Some medications such as hydroxycarbamide or busulphan may damage the sperm in men who are taking these drugs. If you are unsure, it is important to contact your doctors for advice. If you are taking hydroxyurea and want to make your partner pregnant, you will need to stop hydroxycarbamide treatment. During this time you may need to take another drug, for example interferon alpha, to control your MPD. You should allow a wash-out period of approximately three months after stopping hydroxycarbamide for the drug to leave your system. It's prudent to discuss any plans with your haematologist.