Hello, and I hope I can help you today. There is a small amount of sperm in pre-ejaculate, so withdrawal is not a completely reliable form of birth control. 15 percent of women every year who use withdrawl as their mode of contraception get pregnant. If your period is late, I recommend you perform an over-the-counter pregnancy test according to the package directions. It should be positive by now. If you are pregnant, you should begin taking Folic Acid again as it helps to prevent certain types of birth defects. Folic Acid taken before pregnancy has no way to be transmitted to a growing fetus, so it is only really important to take it while you are already pregnant. I hope I was able to answer your question adequately today and that this information was helpful. Best wishes, Dr. Brown