Not all women can donate eggs. Programs vary in the qualities they prefer, but some criteria are fairly standard. Certain rules are set for legal reasons while other policies are designed to increase the chance that a pregnancy will result and that the process will be safe for both donor and recipient. ASRM guidelines state that egg donors should be between the ages of 18-29. In some instances, the IVF physician may recommend that they work with donors who are at least 21 years of age. The lower age limit ensures that a woman can legally enter into a contract. The upper limit reflects the fact that egg quality declines as women age and older women may not respond as well to fertility medications. If egg quality is not good, it increases the odds of abnormalities and birth defects.