Can the on and off or prolonged use of megace (megestrol) es cause birth defects if in the future you decide to have children? what are the concequences?

Category X: Megestrol, or megace, (megestrol) is a progestational drug used to treat severe cachexia, or lack of appetite, in patients with debilitating chronic illnesses ( cancer, AIDS, etc) that prevent good nutrition and can be life-threatening. The drug is a potential teratogen and can cause birth defects if taken in the first trimester of pregnancy, hence category X. Discuss the merits or pitfalls with your OB

Possibly: Agree with above answer and to expand on it, a teratogen exerts it's damage when taken during pregnancy. If you are not taking it from before conception through the pregnancy your risk is considerably lower,