A lesson about prenatal vitamins, their ingredients, and what they do for you and your future baby


By Dr. Liz Kane

When you hear the words “prenatal vitamin,” you’d be justified in thinking these are vitamins you start after a long-awaited positive pregnancy test. There are, however, lots of benefits to starting this nutritional journey earlier. 

Ideally, you’d start taking a prenatal vitamin as soon as you start thinking about trying to conceive, about one to three months before you get pregnant. Many people don’t realize they’re pregnant until they’re well into their first trimester. By then, a great deal of fetal development has already taken place. If you start taking a daily prenatal vitamin before pregnancy, you can set this proverbial nutritional safety net firmly in place, thereby giving yourself and your future baby the best chance of reaping as many benefits as possible—even more so than if you were to simply purchase a prenatal vitamin along with a pregnancy test. Of course, life is unpredictable and sometimes surprises happen, so if you find yourself pregnant before you’ve started a prenatal regimen, just start taking a prenatal as soon as you can.

What to look for in a prenatal vitamin

Now for specifics: What exactly does a high-quality prenatal vitamin contain, and in what foods can you naturally find these nutrients? Let’s review the key ones:

  • Folate: This is the one you’ve likely heard about. Folate is a B vitamin (B9) that provides significant protection against neural tube defects. Neural tube defects are developmental abnormalities of the brain and spinal cord, including spina bifida and anencephaly. There are many different types of folates found in food, but the two most commonly found in dietary supplements are folic acid and 5-L-MTHF, abbreviated MTHF folate. We’ll delve into the difference between MTHF folate supplements and folic acid later, but make sure that whatever prenatal you choose has at least one. Folate can also be found in dark leafy greens, lentils, beans, and legumes. Many foods where folate is not naturally found are fortified with folic acid, especially grains, which you can check on the nutritional info panel.
  • Iron: Your body uses iron to make hemoglobin, the protein that red blood cells use to transport oxygen. In your lungs, hemoglobin binds oxygen and carries it to all the tissues in your body, including a developing embryo via the placenta. The total amount of blood in a woman’s body will increase by 50% during pregnancy, so iron is in high demand. If you feel more tired than usual, it could be because you’re iron deficient, also known as anemia. During pregnancy, doctors will routinely test for anemia by a simple blood test. Iron is found in its highest amounts in red meat (heme iron) but is also naturally present in plant-based sources like dark leafy greens, beans, and dried fruit (non-heme iron). Non-heme iron is best absorbed when it is eaten with a source of Vitamin C, like citrus fruits.
  • Calcium: It’s the mineral used to build your bones and teeth, and for your baby’s, too. Dairy, dark leafy greens, and calcium-fortified orange juice (check the nutritional label) are all good food-based sources of calcium.  
  • Vitamin D: Many nutrients are dependent on another to function or to be absorbed. Vitamin D and calcium have that kind of relationship—you can take as much calcium as you want, but your body won’t be able to absorb it properly without vitamin D. Fatty fish (like salmon) and vitamin D-fortified dairy are good sources. You also get vitamin D from spending time in the sun. Too much sun exposure—especially without protection from sunscreen or clothes—can lead to skin cancer, so if you want to sunbathe or go for a walk in the name of vitamin D, do so in moderation.
  • DHA: This stands for docosahexaenoic acid, an omega-3 fatty acid that supports fetal brain and eye development. It's an integral component of neuronal cell membranes, and intake is tied to the on-time attainment of key developmental milestones and infant problem-solving abilities. It’s found in low-mercury fish and DHA-enriched orange juice, milk, and eggs.
  • Iodine: This mineral helps your baby’s organs and nervous system develop properly. It’s found in iodized salt (usually labeled as such) as well as dairy, fish, and iodine-fortified bread.
  • Choline: Most prenatals lack choline. But growing evidence of its benefits shows choline improves several pregnancy outcomes and protects against certain neural and metabolic disorders.

You might have noticed that all of these vitamins and minerals can be found, to some degree, in food, so why do you need to take a prenatal vitamin on top of all that? For one thing, you need to consume higher amounts of these vitamins than a non-pregnant person, and between pregnancy nausea and strange cravings, it can be hard to meet these nutritional ideals from food alone. 

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Growing babies are effective and efficient at getting what they need from their mothers, and while this is great for their wellbeing, it can have unintended consequences for you. For example, if your diet is lacking in calcium, your baby will leach the calcium they need for their growing skeleton from your own bones. So the benefits of prenatal vitamins and nutrient-high food sources are not just for your future baby, they’re also for you. 

MTHF Folate vs. Folic Acid

With all that mind, there’s another choice to consider, and that’s the question of MTHF folate vs. folic acid. Folic acid is the synthetic form of folate used in mandatory food fortification programs in the United States since 1998 to prevent neural tube defects, such as spina bifida. While a prenatal with folic acid is better than no prenatal at all, we encourage you to choose a prenatal vitamin with MTHF folate. MTHF folate is preferable because it has higher bioavailability, which means your body can utilize MTHF folate directly in its native form. Folic acid needs to be metabolized twice before it is converted into a form that your body can use. Up to 25% of the population is severely impaired in their ability to convert folic acid into its active form and at an increased risk for neural tube defects. The research is still preliminary, but these individuals may benefit from MTHF folate supplementation over folic acid as well. Learn even more about MTHF folate versus folic acid in a longer article here.

Side effects of prenatal vitamins

You might have heard—or perhaps you know from experience—about some of the unpleasant side effects that some women experience while taking prenatal vitamins. We’re sorry to tell you that the most common side effects are ones that you might already deal with during pregnancy, namely nausea and constipation: 

  • For nausea, taking your vitamin at night before you go to sleep, or with food, may bring some relief. 
  • Drinking more water and eating a diet with plenty of soluble fiber can sometimes aid constipation (we recommend trying psyllium capsules to help with digestive discomfort during pregnancy). 

Regardless, if you’re dealing with unpleasant symptoms, be sure to mention this to your doctor or midwife at your next checkup: the best way for you and your unborn baby to reap the benefits of your prenatal vitamins is if you are able to take them regularly, and your care providers should take your concerns seriously.

The take-aways

We know these decisions feel stressful and high stakes, and they are: this is your baby’s development, and it’s normal to want to cover all your bases and do everything you can. It’s a way of feeling more in control in an unpredictable, sometimes-scary time in your life. We encourage you, though, to try and consider your prenatal vitamins as a means to cut yourself a little slack. If, for whatever reason, you’re just not able to follow dietary guidelines for pregnancy to the letter, you can remember that the vitamins you choose are providing a nutritional backup. They’re a support system and an investment in your baby’s health and wellbeing, as well as your own. For all the stress that can seem unavoidable during pregnancy, prenatal vitamins might, ultimately, be a source of relief.