There are a lot of limits on the types of medications and supplements you can take during pregnancy — but prenatal vitamins are not only allowed, they’re strongly recommended.

A good prenatal can help keep you and your growing baby healthy, ensuring that you’re both getting all the nutrients you need to make it through those 9 codependent months of pregnancy.

If prenatal vitamins are for you and baby, though, why do so many healthcare providers tell women to start taking them before pregnancy? Is that safe to do? Also, have you checked out the vitamin aisle lately? It’s chock-full of options.

Don’t stress — we’ve got you covered.

There are two answers here, but (spoiler alert!) neither involves waiting until your first trimester ultrasound.

When you decide to try for a pregnancy

Ready to start a family? In addition to scheduling a well visit with your gynecologist, quitting birth control, and cutting out unhealthy behaviors like smoking, you should start taking prenatal vitamins.

You won’t be able to predict how long it will take you to get pregnant — it could be weeks or months — and you won’t know you’ve been successful until a few weeks after conception. Prenatal vitamins are an important part of preconception care.

As soon as you find out you’re pregnant

If you aren’t already taking prenatal vitamins, you should start as soon as you get a positive pregnancy sign on that pee stick test.

Your OB-GYN may eventually suggest a specific brand or even offer you a prescription to make your vitamin-popping life easier, but you don’t have to wait — every day counts when you’re in the first trimester (more on why in a sec).

Here’s the deal: Pregnancy takes a lot of you. Your cute little fetus is actually a major drain on your body’s natural resources, which is why you spend so much time in those 9 months feeling nauseated, exhausted, achy, crampy, moody, weepy, and forgetful.

Your baby gets all the nutrients it needs directly from you, so it’s easy to become deficient in important vitamins and minerals during pregnancy. Making sure your body has what it needs to nourish both of you is much easier if you get started before baby is in the picture.

Think of it like building up a reserve: If you have more than enough of the vitamins and nutrients you need to thrive, then you can afford to share those vitamins and nutrients with your baby as they grow.

While it’s important to have a well-rounded balance of vitamins and nutrients during pregnancy, some are truly MVPs because they actually help your baby form vital organs and body systems, many of which begin developing in the earliest weeks of pregnancy.

According to the American College of Obstetricians and Gynecologists (ACOG), these are the most important nutrients you need:

Folic acid

The granddaddy of prenatal nutrients, this B vitamin is responsible for creating your baby’s neural tube, or the structure that eventually forms the brain and spinal column. Without a fully developed neural tube, a baby could be born with spina bifida or anencephaly.

Thankfully, the experts are all in agreement here: Folic acid supplements significantly increase the likelihood of healthy neural tube growth. The American Academy of Pediatrics has long held the position that folic acid can reduce neural tube defects by at least 50 percent.

The only catch? The neural tube closes within the first 4 weeks after conception, which is often before or right after a woman realizes she’s pregnant.

Because folic acid is so effective — but only if you’re getting enough at just the right time — the Centers for Disease Control and Prevention recommends that all sexually active women of childbearing age take 400 micrograms (mcg) of folic acid daily (either in a prenatal vitamin or an individual supplement).

That way, you’ll have it when you need it — even if you’re not expecting to! Once you’ve confirmed a pregnancy, you’ll need at least 600 mcg per day.

Iron

Iron supplies the fetus with blood and oxygen, helps build the placenta, and gives you the extra blood volume you need throughout pregnancy. Since pregnant women are prone to anemia, iron supplementation also ensures that you have the right amount of red blood cells in your blood.

Anemia during pregnancy is associated with higher rates of premature delivery and low infant birth weight.

Calcium

Your baby is spending a lot of time in your uterus building up their bones and teeth. In order to achieve this Herculean feat, they need plenty of calcium — which means you need plenty of calcium, too.

If you don’t get enough calcium, your baby will take whatever it needs straight from your bones during pregnancy and breastfeeding. This can lead to temporary bone loss.

Generally speaking, the vitamins and nutrients included in prenatals won’t cause detrimental side effects — if they did, pregnant women wouldn’t be encouraged to take them!

That said, prenatal vitamins do contain levels of nutrients specific to pregnant women, meaning they aren’t always the best choice for nonpregnant people on a long-term basis.

Your iron needs, for example, increase from 18 milligrams to 27 milligrams during pregnancy. While the short-term side effects of too much iron include mild GI upsets like constipation and nausea, over time that excess of nutrients could become more problematic.

Bottom line? If you’re not pregnant or planning a pregnancy, you can hold off on prenatals until you really need them (e.g., a few months before pregnancy, during pregnancy, and — often — for the duration of breastfeeding).

Some celebs swear by prenatals as the secret to their glowing skin and luscious locks because they contain biotin, one of the all-important B vitamins.

And rumors of biotin’s hair, nail, and skin growth powers have circulated forever; many people take biotin supplements for this exact reason.

However, one study after another has failed to prove any significant beauty benefits to taking biotin, leaving the evidence to fall strictly in the anecdotal camp.

Besides biotin, though, there are some extra benefits to prenatals. If you take one with DHA, for example, you’ll be getting a boost of omega-3 fatty acids that may help your baby’s brain and eyes develop.

You may also get thyroid-regulating iodine, which can aid in your baby’s nervous system development.

Finally, there’s some research indicating that taking prenatal vitamins may increase your chances of pregnancy.

To be clear, prenatals are not a magic cure for infertility problems and getting pregnant isn’t as simple as popping a pill. But many of the nutrients included in prenatal vitamins regulate the body systems responsible for making pregnancy possible.

So taking one — when done in conjunction with exercising, eating a healthy diet, and eliminating risk factors like alcohol and drugs — can make it easier to get pregnant more quickly.

There are dozens of options out there, but make sure you check for a few key things before buying a prenatal vitamin:

Regulatory oversight

This is a fancy way of reminding you to make sure some kind of certified organization has verified the health and ingredient claims made by your vitamin manufacturer.

Since the Food and Drug Administration doesn’t regulate any dietary supplements, including prenatal vitamins, look for a thumbs-up from groups like the Office of Dietary Supplements or the U.S. Pharmacopeia Convention.

Doses

Compare the amounts of key nutrients, like iron and folate, in your vitamin to ACOG’s recommended amounts. You don’t want to take a vitamin with too much or too little of what you need.

Over-the-counter (OTC) or prescription

Some insurance providers will cover some or all of the costs of a prenatal vitamin, saving you money. (OTC vitamins aren’t cheap!) If yours does, you may want to ask your provider for a prescription instead of buying your own.

If you still have questions about choosing the right vitamin, feel free to ask your doctor for advice. And, pssst, we have some thoughts on the best prenatals, too.

Suspicious that your prenatals are upsetting your stomach? There are ways you can minimize some of the more unpleasant effects.

  • Ask your doctor about switching to another brand. Sometimes, a prenatal is formulated in a way that just doesn’t sit right with you.
  • Try a different method. Prenatals are often available as capsules, beverages, gummies, and even protein shakes — and ingesting them differently can aid the digestive process. Try switching from one large capsule to three gummies per day or splitting up two doses 12 hours apart.
  • Drink lots of water before and after. If you’re having constipation, make sure you keep your GI system flushed out. You can also add a fiber supplement if you’re really feeling backed up (but get a recommendation from your doctor first).
  • Experiment with food. If your vitamins are making you nauseated, try taking them with or without food. For some people, taking vitamins on an empty stomach is irritating; others find that they can only take them on an empty stomach.

If you’re thinking seriously about becoming pregnant in the next few months, starting a prenatal vitamin should be at the top of your preconception to-do list.

If you’re already pregnant, begin taking one ASAP. It will help your baby grow strong and healthy (and help you stay strong and healthy, too!).

If you’re not seriously considering pregnancy at the moment but technically could become pregnant, stick to a daily folic acid supplement. It will give you what you need should you become pregnant — without loading you up with an unnecessary excess of prenatal nutrients.