In most cases, the answer is no.
There is a whole industry that markets supplements and other products to pregnant women. Even among prenatal vitamins, for most women the only ingredient that is actually required is folate, and that folate is only necessary until the baby’s neural tube is closed, which happens early in the first trimester. The truth is, prenatal vitamins are best taken beginning 2 to 3 months before pregnancy and provide little to no benefit past the first half of the first trimester. In fact, if you are beyond six weeks and prenatal vitamins are making you nauseous or constipated, there’s no reason for you to not stop them.
Aside from the folate in a prenatal vitamin, the other ingredients often found in these vitamins are not science based. Don’t get caught up on buying the most expensive prenatal vitamin because the company says it will make your child smarter or reduce the risks of pregnancy; this simply is not true.
In some cases, due to restrictive diets or preexisting anemia or other risk factors, your doctor might ask you to take an additional supplement or medication.