Why it's important to take prenatal vitamins—even before you’re pregnant

Being pregnant can be scary—so much of the baby’s growth and development is out of your control. But the best way to give your little one a healthy start is to take prenatal vitamins. These supplements can minimize the risks of birth defects, enhance your baby’s development and prevent the depletion of your own vitamin and mineral supply. Because of these benefits, the Society of Obstetricians and Gynecologists of Canada recommends them for all pregnant women.

Choosing a supplement

If you already take multivitamins, you might wonder if it’s necessary to buy prenatal vitamins, but they really are different: Prenatal vitamins have higher amounts of a few star baby-growing nutrients, so it’s best to switch over to them even before you try to conceive.

Experts say it doesn’t matter which specific prenatal vitamin you choose. “All prenatal vitamins are slightly different from one another,” says Batya Grundland, a family physician and the maternity care lead at Women’s College Hospital, “but it doesn’t seem to matter which one you take.” That’s because they’re consistent in the most crucial ingredients: folate and iron.

The importance of folate

Also known by its synthetic version, folic acid, folate reduces the risk of neural tube defects. “There are rare congenital anomalies where the spinal cord and neural tube do not develop completely,” says Grundland. “By supplementing with folate, you reduce the chance of that congenital malformation.”

The risk for this defect is highest in the first trimester, especially during the first few weeks of pregnancy, which is why it’s ideal to start taking prenatal vitamins three months before conception. And since it’s difficult to get the required daily dose of 0.4 to 0.8 milligrams from food—even if you do eat folate-rich spinach, asparagus and liver—health professionals recommend supplementation regardless of diet.

If your growing baby is considered high risk because you’ve previously had a child with a neural tube defect or you have a body mass index of more than 35, your doctor may prescribe a higher dose.

Stocking up on iron

Iron is the second key nutrient in prenatal vitamins because it’s needed to make red blood cells, and women gain more blood mass while they’re pregnant, explains Kerri Cuthbert, a dietitian with the Winnipeg Regional Health Authority. “Plus, it supports normal brain development in the baby.”

The average woman requires about 18 milligrams of iron per day (compared to the 8 milligrams required by men), while pregnant women need 27 milligrams daily, especially in the last trimester when the baby begins storing enough iron to last for the first six months of life. Many women become iron deficient during pregnancy because the fetus takes whatever iron it needs. If you have a blood test showing you’re iron deficient, your physician may recommend additional iron supplements to return levels to normal.

Additional nutrients

As for all those other ingredients listed in your prenatal vitamin? “There’s not one nutrient that you need more than another,” says Grundland. But since ingesting extra nutrients doesn’t seem to be harmful and may help, a prenatal vitamin with a laundry list of ingredients is de rigueur.

The only concern? If you’re already taking other supplements or herbal remedies. For example, vitamin A, which is found in cod liver, fish oil and prenatal vitamins, can cause birth defects when taken in high doses, so it’s best to talk to your doctor before adding any new supplement into your rotation.

You might also notice things like probiotics and omega-3 fatty acid supplements marketed to pregnant women alongside the prenatal vitamins in the supplement aisle. But for those, says Grundland, “the evidence is limited.” In other words: Don’t bother and focus on a healthy diet instead.

Ideally, you should be getting as many nutrients as possible from food, with plenty of calcium and vitamin D (both found in dairy, fortified milk alternatives, sardines and salmon), as well as omega-3s (in nuts, seeds, soy, salmon, herring, mackerel, clams and mussels). But if you’re unable to maintain a balanced diet because of limited access to healthy food, food allergies, dietary restrictions or medical conditions, a prenatal vitamin will pick up the slack.

When to take them

Typically, prenatal vitamins are taken in the morning on an empty stomach. If your daily dose causes nausea, take it with food or at night if your morning sickness is confined to the morning. And if you really can’t keep it down or find that it causes constipation—both of which are possible side effects of iron intake—skip the multi and take a supplement of just folate.

And don’t quit your prenatal vitamins after birth—it's a good idea to pop them for at least four to six weeks after, or until you stop breastfeeding, to protect both you and your baby from nutrient depletion and to start your first months together off right.