Getting adequate nutrition is especially important for mothers-to-be. Prenatal vitamins fill any gaps in your nutrition, ensuring that your growing baby has all the vitamins they need. So what are the most important vitamins for pregnant women or those trying to conceive? 400 micrograms of folate per day has been shown to reduce fetal neural tube defects. 30 to 60 milligrams of iron per day will help your body keep up with the additional blood supply that the baby demands. 200 milligrams of DHA will provide a fatty acid crucial to fetal brain development. 150 micrograms of iodine and 450 milligrams of choline are important for hormone regulation, fetal growth and brain development.