Some women with very healthy and varied diets may already get enough essential nutrients through their diet.
But many women take prenatal supplements to ensure they are getting a full range of vitamins and minerals to support themselves and the developing fetus properly.
This article discusses the most important prenatal vitamins and why they are necessary.
What are prenatal vitamins?
Prenatal vitamins are often available in one multivitamin supplement.
Prenatal vitamins are nutritional supplements that usually contain a concentrated mix of minerals and vitamins that a woman’s body needs more of during pregnancy.
Ideally, a woman will take prenatal vitamins while trying to become pregnant, and while she is breastfeeding.
Some women take the individual prenatal nutrients as separate supplements, but it is often easier to take them in one multivitamin supplement.
Taking specific prenatal vitamins may reduce the risk of complications, for both the mother and the developing fetus as well as help a mother go full term.
Neural tubes are embryonic structures that eventually form the spine and brain of the fetus. Neural tube defects can cause serious spine and brain conditions, including spina bifida, a condition where parts of the backbone do not close properly.
Folic acid also helps a pregnant woman’s body make red blood cells, potentially reducing the risk of anemia. Anemia may cause pregnancy complications, such as:
- low birth weight
- premature birth
- infant anemia
Other vitamins and nutrients
Aside from folic acid, several other key nutrients can benefit pregnant and breastfeeding women and developing fetuses. These include:
Iron: Pregnant women need about twice the usual recommended amount of the mineral iron. Iron is another crucial component in red blood cells. Pregnant women who do not get enough iron may develop iron-deficiency anemia.
Zinc: Supports the immune system and helps the body make proteins, divide cells, and synthesize DNA for new cells.
Vitamin B-12: Helps the body make healthy red blood cells and neurons, which are the specialized cells found in the spinal cord and brain. B-12 also helps these cells to function properly.
Calcium and vitamin D: Work together to help develop fetal bones and teeth. Vitamin D is also crucial for healthy eye and skin development. Calcium may reduce the risk of preeclampsia, a leading cause of illness and death in pregnant women, and newborns.
Vitamin A: Helps cells grow and differentiate, contributing to the healthy development of vision and many vital organs.
Iodine: A trace element essential for the development of the central nervous system, brain, and skeletal system. Severe iodine deficiencies in pregnant women may slow fetal growth or cause neurodevelopmental defects, stillbirth, or miscarriage.
Best prenatal vitamins to take
There are many different prenatal vitamins to choose from, including those available at a pharmacy or online. A doctor may sometimes prescribe prenatal vitamins to women with particular health considerations.
Deciding which prenatal supplements to buy comes down to what they contain. Different women will need different doses of some vitamins and minerals, depending on factors such as diet, age, and activity levels.
Typically, a good prenatal vitamin for most women over 19 years of age should contain:
- Folic acid: At least 400 micrograms (mcg) before pregnancy, 600 mcg during pregnancy, and 500 mcg when breastfeeding.
- Vitamin B-12: 2.6–2.8 mcg.
- Iron: 27 milligrams (mg) in pregnancy and 9–10 mg when breastfeeding.
- Calcium: 1,000–1,300 mg.
- Vitamin D: 600 international units (IU).
- Zinc: 11 mg during pregnancy and 12 mg during breastfeeding.
- Vitamin A: 750–770 mcg for pregnancy and 1,200–1,300 mcg for breastfeeding.
- Vitamin B-6: 1.9–2.0 mg.
- Iodine: 220 mcg during pregnancy and 290 mcg during lactation.
Prenatal vitamins often contain omega-3 because some pregnant women do not get enough from their diet.
Several other nutrients are also common constituents of prenatal multivitamins, but nutritionists know less about their benefits or how and when to take them.
One example of this is omega-3 fatty acids, compounds that help give structure to cell membranes, especially those in the brain and retina.
According to the National Institutes of Health (NIH), the daily intake need by pregnant women is 1.4 grams (g) and 1.3 g per day for breastfeeding women, compared to 1.1 g per day for other women 14 years of age and older.
But a 2015 systemic review that examined nearly 150 studies looking at the impact of omega-3 supplementation on maternal and fetal health found only a small increase in gestation time and birth weight.
So, while it might not hurt for a prenatal vitamin to include omega-3s, it may not be as necessary as once thought.
Omega-3 fatty acids are commonly in prenatal vitamins because some pregnant women may struggle to get enough in their diet.
Fish and seafood are common sources of omega-3s, but many species contain high levels of mercury that research has associated with birth abnormalities.
Prenatal vitamins with fish or seafood content should only come from species typically low in mercury, such as:
Seafood species to avoid when pregnant or breastfeeding include:
- king mackerel
- orange roughy
- white tuna
If a person has concerns about omega-3 fatty acids from fish or seafood, they can consider plant-based foods and supplements instead.
Vitamins E and C
The NIH also recommend 15–19 mg of vitamin E a day for anyone pregnant or breastfeeding.
Research once suggested taking vitamin E and C together during pregnancy might reduce oxidative stress and its associated complications, such as:
- pre-labor rupture of membranes (PROM)
- intrauterine growth restriction
However, the World Health Organization (WHO) currently say that a joint vitamin C and E supplement likely has little impact on women or developing fetuses, and may increase the risk of PROM.
When to start taking them
Ideally, women should start taking prenatal vitamins a few months before becoming pregnant and continue while breastfeeding.
For example, women may want to start taking 400–800 mcg of folic acid daily for at least three months before becoming pregnant and throughout their pregnancy, to reduce the risk of neural tube defects.
Many women start taking prenatal vitamins after they find out they are pregnant.
Women with underlying health conditions should speak with their doctor or pharmacist before taking prenatal vitamins to avoid possible complications or interactions.
Nutrients in prenatal vitamins can cause side effects, mostly mild to moderate digestive discomfort such as:
But women usually only experience more serious or severe side effects when they take too many prenatal vitamins or very high doses of specific vitamins.
One notable example to be aware of concerns vitamin A. This is because taking more than 10,000 IU or 3,000 mcg of vitamin A can cause birth abnormalities, as well as bone loss and liver damage.
Women who experience side effects of prenatal vitamins or symptoms they cannot explain should usually stop taking the vitamins, and talk with a doctor or pharmacist. Women who experience severe side effects should seek emergency medical attention.
Any pregnant woman on existing medication should talk to their doctor before taking a prenatal supplement.
Specific considerations, such as which prenatal vitamin to take, when to take it, and how to take it depends largely on individual factors.
Many multivitamin supplements contain the correct amounts of prenatal vitamins, though usually not those for pregnant or breastfeeding women.
Vegetarian and vegan women may need prenatal vitamins with higher doses of nutrients that can be difficult to get from plant sources alone, such as:
- vitamin B-12
- B-2 (riboflavin)
- vitamin D
Vegetarian and vegan women may also want a prenatal vitamin that comes in tablet form or capsules with plant-based coatings rather than coatings containing gelatin.
Pregnant women taking any regular medications or supplements should talk with a doctor before choosing a vitamin supplement.
Several prescriptions, over-the-counter, and herbal supplements can negatively interact with prenatal vitamin ingredients, including:
- blood thinners
- St. John’s wart
- breathing medications (theophylline)
- proton-pump inhibitors
A woman can take prenatal vitamins any time of the day, but it is usually best to avoid taking them too close to bedtime. Women with morning sickness can also take vitamins later in the day.
Some prenatal nutrients are best absorbed in smaller doses, especially calcium, so many prenatal vitamins are best taken once or twice daily.
Spreading out vitamin doses, and taking them with food and water, may reduce the risk of minor side effects. Women who continue to have minor side effects from prenatal vitamins after these considerations can try different brands or formulas.
Certain vitamin and mineral supplements may reduce the risks of serious birth abnormalities and maternal complications.
Important nutrients for women to take before conceiving, and during pregnancy or breastfeeding, include:
- folic acid
- vitamin B-12
- vitamin B-6
- vitamin D
- vitamin A
A good prenatal multivitamin contains the above nutrients in doses recommended by health authorities. Choose supplements free of fillers, toxins, binders, and heavy metals.
A doctor or pharmacist can help women to find a prenatal vitamin that addresses their health concerns and dietary considerations while avoiding possible interactions or complications.