A well-rounded (one that contains the right amount of each vitamin) prenatal vitamin should be started prior to conception, if you are trying to get pregnant, but if not it should be started as soon as you know your pregnant.
Whole food-based prenatal vitamins are recommended for the best absorption without synthetic ingredients. However, normal prenatal vitamins are usually fine as well. A good prenatal vitamin will give a well-rounded variety of all of the supplemental vitamins and minerals needed.
If your prenatal vitamin is shy of the specific recommended daily nutrients below, supplement with additional food or supplement sources. The following dosage recommendations are averages. Your doctor may recommend alternate doses of the following nutrients depending on your specific needs.