A good prenatal vitamin covers most of what you and your baby need, but knowing exactly which nutrients matter (and how much) helps you choose the right one and fill any gaps. The core list includes folic acid, iron, calcium, vitamin D, DHA, iodine, and choline. Here’s what each one does and how much you need.
Folic Acid: Start Before You Conceive
Folic acid is the single most time-sensitive supplement in pregnancy. It helps prevent neural tube defects, which are serious problems with the brain and spinal cord that form in the earliest weeks, often before you even know you’re pregnant. That’s why the CDC recommends all women who could become pregnant take 400 mcg of folic acid every day, not just those actively trying.
ACOG sets the bar slightly higher at 600 mcg daily once you are pregnant. If you’ve had a previous pregnancy affected by a neural tube defect, the recommendation jumps to 4,000 mcg daily, which requires a separate prescription-strength supplement beyond your prenatal vitamin. Large randomized controlled trials in the 1990s established this protective effect, and folic acid supplementation has been standard prenatal guidance ever since.
Iron: Protecting Your Blood Supply
Your blood volume increases dramatically during pregnancy, and iron is what your body uses to make the hemoglobin that carries oxygen through that expanded blood supply. ACOG recommends 27 mg of iron per day during pregnancy. Many experts suggest starting a routine supplement of 30 mg of ferrous iron around week 12.
Iron deficiency during pregnancy isn’t just about feeling tired. In a large study of more than 54,000 pregnancies, anemia before 24 weeks of gestation was linked to higher rates of low birth weight, preterm birth, and infant death around delivery. Maintaining adequate iron also builds a buffer against the blood loss that occurs during delivery itself. If you’re diagnosed with iron deficiency anemia, treatment doses are significantly higher, typically 60 to 120 mg daily.
Iron is easier to absorb when paired with vitamin C, so taking your supplement with a glass of orange juice or alongside a meal that includes fruits or vegetables can help. Iron supplements commonly cause constipation or nausea. Taking them with food or switching to a slow-release formula often helps.
Vitamin D and Calcium: Building Bones
Your baby’s skeleton draws heavily on your calcium and vitamin D stores, especially in the third trimester. The recommended daily calcium intake is 1,000 mg for women ages 19 to 50 and 1,300 mg for those 14 to 18. Most prenatal vitamins contain only a fraction of that, so dairy products, fortified foods, or a separate calcium supplement may be needed to close the gap.
For vitamin D, the Institute of Medicine set the adequate intake during pregnancy at 600 IU per day. Most prenatal vitamins contain only about 400 IU per tablet. If blood work shows you’re deficient, most experts consider 1,000 to 2,000 IU daily safe during pregnancy, with an upper ceiling of 4,000 IU. Vitamin D helps your body absorb calcium efficiently, so the two nutrients work as a pair.
DHA Omega-3: Fuel for Brain and Eye Development
DHA, a type of omega-3 fatty acid, concentrates in the brain and retina and accumulates most rapidly during the third trimester. Retinal development wraps up by birth, while brain accumulation continues through the first two years of life. Clinical guidelines recommend pregnant women consume at least 200 to 300 mg of DHA daily on top of a baseline of 250 mg of combined DHA and EPA that’s recommended for all adults.
If your diet is low in fatty fish and you’re getting less than 150 mg of DHA per day, a guideline published in the American Journal of Obstetrics & Gynecology recommends 600 to 1,000 mg of DHA (or DHA plus EPA) daily starting no later than 20 weeks. Beyond brain development, omega-3 supplementation during pregnancy has been shown to reduce the risk of preterm birth by 11% and early preterm birth (before 34 weeks) by 42%. Many prenatal vitamins don’t include DHA, so check the label and add a standalone fish oil or algae-based DHA supplement if yours doesn’t.
Iodine: Supporting Thyroid and Brain Function
Iodine is easy to overlook, but it’s essential for thyroid hormone production, which in turn drives your baby’s brain development. The recommended intake during pregnancy is 220 to 290 mcg per day. ACOG lists 220 mcg as the daily target, and prenatal vitamins should contain at least 150 mcg.
The consequences of deficiency are serious. Low thyroid hormone during pregnancy increases the risk of miscarriage, preterm delivery, and poor fetal growth. Severe iodine deficiency can lead to hearing problems and significant learning disabilities in the child. Even mild deficiency may affect learning and behavior, though the evidence there is less conclusive. Iodized salt, dairy, and seafood are good dietary sources, but not all prenatal vitamins include iodine, so check the label.
Choline: The Overlooked Nutrient
Choline has gained attention in recent years as research reveals its importance for fetal brain development. The recommended intake is 450 mg per day in early pregnancy (up to 12 weeks), rising to 550 mg daily after that. For comparison, non-pregnant women need about 425 mg. Most prenatal vitamins contain little to no choline, which makes dietary sources like eggs, liver, and soybeans particularly important.
Research suggests children exposed to higher choline levels in the womb may show improved cognitive function, memory, and attention later in life. Choline supplementation is also being studied as a potential way to reduce the risk of developmental disorders. If your prenatal vitamin doesn’t include choline, a separate supplement or deliberate dietary focus can help you reach adequate levels. Two to three eggs per day, for example, provide roughly 300 mg.
Vitamin B6: Relief for Morning Sickness
If nausea is making your first trimester miserable, vitamin B6 has solid clinical evidence behind it. ACOG recommends 10 to 25 mg of vitamin B6 three or four times a day to treat pregnancy-related nausea. In randomized trials, 30 to 75 mg daily significantly reduced nausea compared to a placebo. When combined with an antihistamine called doxylamine, the combination reduced nausea and vomiting by 70% and lowered hospitalization rates.
Your prenatal vitamin already contains some B6 (typically around 2 mg), so any additional supplementation for nausea should be discussed with your provider, since higher therapeutic doses approach the tolerable upper limit.
What to Avoid
Preformed vitamin A is the most important supplement to watch. It comes from animal sources, fortified foods, and many multivitamins. A landmark study in the New England Journal of Medicine found that women who consumed more than 10,000 IU of supplemental preformed vitamin A per day had nearly five times the rate of certain birth defects compared to women taking 5,000 IU or less. The risk was concentrated in women who took high doses before the seventh week of pregnancy. Beta-carotene, the plant-based form of vitamin A found in carrots and sweet potatoes, does not carry this risk. Check your prenatal vitamin to confirm its vitamin A comes from beta-carotene rather than retinol, or that the retinol dose stays well under 10,000 IU.
Several herbal supplements are also contraindicated during pregnancy. Black cohosh, blue cohosh, pennyroyal, and rue can all stimulate uterine contractions. Aloe vera taken internally (whole leaf preparations, not topical gel) carries similar risks. Wormwood contains a potentially neurotoxic compound. As a general rule, avoid herbal supplements during pregnancy unless you’ve specifically confirmed their safety.
Choosing and Timing Your Prenatal Vitamin
A standard prenatal vitamin should cover folic acid, iron, iodine, vitamin D, calcium (at least partially), and B vitamins. You’ll likely need to add DHA and possibly choline separately, since most formulas fall short on both. Look at the label for specific amounts rather than assuming “prenatal” on the bottle means all your bases are covered.
Ideally, start your prenatal vitamin at least one month before trying to conceive, primarily so folic acid levels are adequate during the earliest weeks of fetal development when the neural tube forms. If your pregnancy was unplanned, start as soon as you find out. Iron supplementation becomes most important from the second trimester onward, when blood volume expansion accelerates. DHA matters most in the third trimester when fetal brain accumulation peaks, but starting earlier gives you a consistent baseline.
If your prenatal vitamin makes you nauseous, try taking it with food, switching to a different brand, or taking it at bedtime. Gummy prenatals are easier on the stomach but typically lack iron and may have lower amounts of other nutrients, so read the label carefully and supplement individually if needed.