Prenatal Vitamins: When to Start, What to Look For and Side Effects

Prenatal vitamins are daily multivitamins made for people who are pregnant or could become pregnant, and the most important ingredient is folic acid: the CDC says that if you could become pregnant, you should get 400 mcg of folic acid daily to help prevent neural tube defects.

Prenatal vitamins are multivitamins made for pregnancy and for anyone who could become pregnant, and the one thing that matters most is folic acid: the CDC says the U.S. Public Health Service recommends 400 mcg of folic acid daily if you could become pregnant. Start before conception if you can, because the CDC says neural tube defects happen in the first few weeks of pregnancy, often before you know you are pregnant.

Below: which nutrients to look for, how to read a label, gummies vs pills, side effects and when to call your provider, all drawn from the CDC, USPSTF, NIH, FDA, Mayo Clinic and Cleveland Clinic.

What Are Prenatal Vitamins?

Mayo Clinic describes prenatal vitamins as a way to fill nutrient gaps for people who are pregnant or trying to conceive, not a replacement for a healthy diet. According to Mayo, folic acid helps prevent neural tube defects (serious abnormalities of the baby’s brain and spinal cord), and iron supports the placenta and fetus and helps your body make the blood that carries oxygen to your baby.

The NIH Office of Dietary Supplements (ODS) notes that ACOG and the Academy of Nutrition and Dietetics recommend a daily prenatal supplement, and that the Dietary Guidelines for Americans say prenatal supplements may be especially important for folate, iron, iodine and vitamin D.

When Should You Start Taking Prenatal Vitamins?

Before you get pregnant, if you can. The CDC explains that NTDs, major birth defects of the brain and spine, happen in the first few weeks of pregnancy, and that by the time you realize you are pregnant, it might be too late to prevent one. The sources word the timing differently:

• USPSTF (2023, grade A): all persons planning to or who could become pregnant should take a daily supplement containing 0.4 to 0.8 mg (400 to 800 mcg) of folic acid, starting at least 1 month before anticipated conception and continuing through the first 2 to 3 months of pregnancy.
• CDC: 400 mcg of folic acid daily if you could become pregnant, even if you are not planning a pregnancy.
• Mayo Clinic: start extra folic acid at least 3 months before pregnancy, if possible.
• Cleveland Clinic: ideally one to three months before trying to conceive.

The USPSTF notes that nearly half of all pregnancies in the U.S. are unplanned. If you just found out you are pregnant and have not been taking anything, call your provider now rather than waiting for your first visit. Our first trimester guide covers what else happens in those early weeks.

What Should Be in a Prenatal Vitamin?

There is no single recipe. ODS says no standard federal definition exists for the ingredients or doses in prenatal supplements, so formulas vary widely. Mayo Clinic suggests checking the label for folic acid, iron, calcium and vitamin D first. Your provider should set the amounts.

• Folic acid vs other folate forms: ODS notes that some prenatals use 5-MTHF (often sold as methylfolate) instead of folic acid, and that the neural tube evidence applies to folic acid. Ask your provider about other forms.
• Iodine is not in every prenatal: per ODS, which adds that vegetarians, vegans and people who skip iodized salt are at higher risk of low intake.
• Choline is often low: ODS reports fewer than half of prenatals contain it, usually in small amounts.
• DHA may be a separate pill: Cleveland Clinic says not all prenatals contain DHA; Mayo says your provider might suggest omega-3 supplements if you do not eat fish.

How to Choose a Prenatal Vitamin

Your provider may recommend a brand or leave the choice to you (Mayo Clinic). Read the Supplement Facts label with this checklist:

• Folic acid: CDC: 400 mcg daily if you could become pregnant; USPSTF: 400 to 800 mcg.
• Iron, iodine, choline, calcium and vitamin D: check each is listed. The label should list the amount; compare it with what your provider recommends.
• DHA: included, or sold as a separate softgel? Ask whether you need it.
• One product only: Mayo advises against taking extra prenatal vitamins or multivitamins beyond what you need daily, and warns that high doses of some vitamins may be harmful to your baby.
• A third-party quality seal: ODS recommends a product tested by an independent quality organization, naming U.S. Pharmacopeia (USP), NSF and ConsumerLab as examples.

Why the seal matters: the FDA states that it is not authorized to approve dietary supplements for safety and effectiveness before they are marketed, and advises talking to your doctor, pharmacist or other health care professional before using one. ODS describes a government review in which 11 of 12 over-the-counter prenatal products tested had at least one nutrient outside acceptable deviations from the label.

Taking sleep aids or herbal products too? Ask first: see our guide on melatonin during pregnancy.

Prescription vs Over-the-Counter Prenatal Vitamins

Both exist. Cleveland Clinic says most prenatals are sold over the counter, and a pregnancy care provider can also prescribe one. Prescription does not mean stronger across the board: ODS describes a 2017 label review that found prescription products listed more folic acid, while nonprescription products listed more iodine, calcium, vitamin A and vitamin D.

Gummy vs Pill Prenatal Vitamins

If you prefer a gummy, know the trade off. ODS says gummy formulations often contain no iron and often contain no calcium. If your gummy lacks iron, ask your provider whether you need it separately.

Prenatal Vitamin Side Effects and How to Ease Them

Cleveland Clinic names constipation and nausea as the two most common side effects, and Mayo Clinic says the iron in prenatals can sometimes cause constipation. What the two sources suggest:

• Constipation: drink plenty of fluids, eat more fiber and stay active with your provider’s okay (Mayo). Ask your provider before using a stool softener.
• Nausea: taking the vitamin after a meal may help (Cleveland Clinic).
• Still struggling: try a different brand (Cleveland Clinic) or ask your provider (Mayo).
• No catching up: Cleveland Clinic says not to take extra prenatals to fill gaps; your provider will recommend or prescribe more if needed.

If nausea and vomiting are so severe that you cannot keep fluids down, the CDC lists that as an urgent maternal warning sign: contact your provider right away rather than just skipping the vitamin. Other stomach trouble is covered in our guide to diarrhea during pregnancy.

Do You Still Need Food First?

Yes. Mayo Clinic calls a healthy diet the best way to get the vitamins and minerals you need. Food also covers what your pill may lack, such as choline or iodine (see the table above). ODS adds that vitamin C helps you absorb iron from plant foods, and that calcium can interfere with iron absorption.

More is not better. ODS states that excessive preformed vitamin A can cause birth defects (beta carotene from plant foods is not part of that concern), and Mayo warns that extra vitamin A can potentially harm your baby. Stick to one prenatal unless your provider adds something specific.

Prenatal Vitamins While Breastfeeding

The CDC says breastfeeding mothers generally need more calories than before pregnancy, that needs for nutrients including iodine and folate rise during lactation, and that diet alone may not ensure adequate nutrition, so a multivitamin may help. The CDC leaves the choice to your provider, including whether you need iodine, and for vegetarian or vegan diets, vitamin B12 and omega-3s. Ask about your vitamin plan at your postpartum visit. See our guide on how to breastfeed.

Can Prenatal Vitamins Help You Get Pregnant?

None of the primary sources we reviewed (CDC, USPSTF, NIH ODS, Mayo Clinic, Cleveland Clinic) describe prenatal vitamins as a way to make conception more likely. Their reason for starting early is to have folic acid in place when the neural tube forms.

Once you have a positive test, our guides to implantation bleeding and the week by week pages for 11 weeks, 14 weeks and 20 weeks pregnant walk you through what comes next.

Planning Ahead for Baby’s Sleep

Betteroo’s State of Parent and Baby Sleep 2026 (October edition), a survey of 83,901 parents who came to Betteroo for sleep help (not a random sample), found 80% of parents get under 6 hours of sleep. Our safe sleep environment guide is a good place to start planning.

Related Betteroo Guides

• First trimester guide
• 11 weeks pregnant
• 4 weeks pregnant
• Melatonin while pregnant
• Chamomile tea during pregnancy
• How to breastfeed

When to Call Your Provider

Call your provider if:

• You had a past pregnancy with a neural tube defect: the CDC says to talk with your doctor first if you are planning another pregnancy. Ask about a higher amount of folic acid and when to start it.
• You cannot keep vitamins, food or fluids down: the CDC lists severe nausea and vomiting, such as not keeping fluids down, as an urgent warning sign.
• You have been told you have anemia: Cleveland Clinic says your provider may recommend an additional iron supplement. Do not add iron on your own.
• You want to take any supplement beyond your prenatal: such as extra iron, vitamin A, DHA or herbal products. The FDA advises asking a health care professional first.

Seek medical care immediately for any CDC Hear Her urgent maternal warning sign, which applies during pregnancy and in the year after delivery: a headache that will not go away or gets worse; dizziness or fainting; vision changes; a fever of 100.4 degrees F (38 degrees C) or higher; extreme swelling of the hands or face; thoughts of harming yourself or your baby; trouble breathing; chest pain or a fast or irregular heartbeat; severe nausea and vomiting; severe belly pain that does not go away; your baby’s movement stopping or slowing; vaginal bleeding or fluid leaking during pregnancy; heavy bleeding or clots after pregnancy; severe swelling, redness or pain in a leg or arm; or overwhelming tiredness. If it feels like an emergency, such as chest pain, trouble breathing or fainting, call 911 or go to the nearest emergency room. Our preeclampsia guide explains why some of these signs matter.

This article is general education, not medical advice. Your own provider’s instructions come first.

Frequently Asked Questions

Related Betteroo Guides

• 16 weeks pregnant