If you are planning to become pregnant, it is ideal to have a full menstrual cycle before you try to conceive. You can more accurately calculate the fetus's age by counting from the first day of your last menstrual period before you became pregnant.
The amount of time it takes for a woman's full fertility to return after stopping birth control varies for each woman and depends on the birth control method she is using. Your ability to get pregnant gradually decreases as you age, starting at age 25. Poor health and irregular periods may also decrease your fertility. After you stop any form of birth control, you may have a more difficult time getting pregnant simply because you are older than when you started using birth control.
If you get pregnant shortly after stopping the Pill, don't worry. Using oral contraception just before a pregnancy doesn't increase the risks of miscarriage or fetal problems. However, if you do not have a normal menstrual cycle before you become pregnant, it might be a little harder to accurately predict your due date.
If you are planning to become pregnant, it is a good idea to start taking a multivitamin that contains folic acid (400 micrograms). Taking this vitamin in early pregnancy can reduce your chances of having a baby with certain birth defects.
WebMD Medical Reference from Healthwise