The very important thing to take is folic acid, which you can take alone (i.e., without the whole rest of the prenatal group attached to it). If you have been told not to take prenatals because they won't stay down or something like that, a folic acid tablet is small, not irritating to the stomach, and should stay down fine. And it is extremely important to the baby's health, not only during pregnancy but especially in the three months before pregnancy.