Vitamins and minerals during pregnancy

Although all vitamins and minerals contribute to the proper functioning of the human body, some are essential for pregnant women: folic acid, iron, calcium, vitamin D, fibre, iodine, choline, and omega-3 fatty acids. They play a major role in all stages of growth of the embryo and the fetus.

Why take vitamin and mineral supplements?

Pregnant women are advised to take a daily prenatal vitamin and mineral supplement. Sometimes, a woman’s diet doesn’t provide enough of certain nutrients that play a crucial role in pregnancy. A multivitamin helps fill any nutritional gaps that a woman may have during her 9 months of pregnancy.

It should contain 0.4–1 mg of folic acid and 16–20 mg of iron. Quantities may vary depending on your doctor’s recommendations.

The Society of Obstetricians and Gynaecologists of Canada states that, in addition to prenatal multivitamins, a pregnant woman may need to take calcium, vitamin D, or iron supplements depending on her diet and state of health. Discuss this option with your doctor.

Folic acid (vitamin B9)

This vitamin is important, especially in early pregnancy. In the first few days following conception, it plays a vital role in the formation of the baby’s spinal cord and brain.

If you wait until you’re pregnant to take a multivitamin, a crucial stage of development will have already passed. That’s why doctors advise women who are planning to get pregnant to take a multivitamin containing folic acid two to three months before conceiving. It’s recommended that all women who can become pregnant, whether they intend to or not, should take a folic acid supplement every day.

Throughout pregnancy, folic acid is involved in the formation of the brain and nervous system, new tissues, and blood cells. Folic acid deficiency can cause growth retardation, birth defects, and neural tube defects (for example, spina bifida). Severe physical or mental disabilities may occur as a result.

Pregnant women’s daily folic acid requirements range from 0.4 mg to 1 mg. Women who have a family or personal history of neural tube defects need an even higher dose.

In Canada and the United States, folic acid is added to white flour, and is usually added to corn flour and pasta. However, pasta made in Italy isn’t fortified with folic acid, so be sure to check the list of ingredients.

Iron

Iron is found in red blood cells. It allows these cells to capture oxygen from the lungs and transport it throughout the body and to the fetus through the placenta. Pregnant women need more iron because their blood volume increases. Plus, they need to provide iron to their unborn baby. A baby’s iron stores at birth last for the first 6 months of life at most.

Adequate iron intake reduces the risk of preterm birth, low birth weight, and infant mortality.

Iron deficiency may cause anemia. It can also cause fatigue and more rapid shortness of breath on exertion. Iron deficiency can be detected by a blood test. Vegetarian women and those who have close or multiple pregnancies are at greater risk of iron deficiency.

Other sources of iron

Certain vegetables such as greens (e.g., kale, spinach, asparagus, snow peas), beets, and unpeeled potatoes contain some iron. However, iron from plant foods (e.g., vegetables, legumes, fortified breakfast cereal, and nuts) and eggs isn’t absorbed as well as iron from meat and fish. That’s why vegetarians must consume twice as much iron to meet their needs.

How to promote iron absorption

When you eat plant foods that contain iron, serve them with a fruit or vegetable that’s rich in vitamin C (e.g., bell peppers, tomatoes, turnips, cauliflower, broccoli, sweet potatoes, Brussels sprouts, grapefruit, clementines, tangerines, strawberries, raspberries, kiwi, melons, mangoes). This will help your body absorb the iron.

Furthermore, avoid drinking tea or coffee during a meal or in the hour before or after a meal, as these beverages contain substances that interfere with the absorption of iron and calcium.

Calcium

Pregnant women need to increase their calcium intake by 30 percent so their baby gets the necessary amount. Calcium helps build bones and teeth. If your diet isn’t rich enough in calcium, your body will deplete its own stores for the sake of the baby. Calcium also helps maintain good blood pressure during pregnancy.

If you don’t eat many calcium-rich foods, you may need to take supplements. Taking 1 g of calcium per day helps reduce the risk of preeclampsia (high blood pressure during pregnancy) in women with inadequate calcium intake. In Canada, approximately 41 percent of women aged 19 to 50 aren’t getting enough calcium in their diet. Consider seeking advice from a nutritionist.

Vitamin D

Vitamin D helps to increase the absorption of calcium and build bones. It’s also involved in cell growth and immune system function. Adequate vitamin D levels during pregnancy provide lifelong benefits to the mother and her child.

Although many foods contain or are fortified with vitamin D, we get most of ours from sunlight. That’s why people who live in northern countries, such as Canada, often have inadequate levels of vitamin D from October to April. Therefore, even if you eat foods that contain vitamin D, you may still be advised to take supplements. Prenatal multivitamins usually contain vitamin D.

Studies suggest that vitamin D supplementation may help pregnant women reduce their risk of preeclampsia, gestational diabetes, and low birth weight.

*It’s safe for pregnant women to eat canned light tuna. However, they should limit their consumption of fresh or frozen tuna and canned albacore tuna. For more information, see our fact sheet, Healthy eating during pregnancy.

Omega-3 fatty acids

There’s mounting evidence that omega-3 fatty acids are extremely beneficial during pregnancy. These good fats contribute to the development of the baby and the mother’s health. Omega-3 fatty acids play a role in the development of the baby’s brain and eyes. They have also been shown to lower the mother’s risk of depression throughout her pregnancy and after giving birth.

In general, people don’t get enough omega-3 fatty acids from their diet. For this reason, pregnant women are advised to eat at least two servings of fatty fish per week (200–350 g of cooked fish).

An analysis of 70 studies concluded that taking omega-3 supplements during pregnancy reduced the risk of preterm births (before 37 weeks) and very preterm births (before 34 weeks). Women with low-risk pregnancies, however, don’t stand to benefit from an omega-3 supplement. Taking one doesn’t have any drawbacks, but it’s best to simply eat fish; when omega-3 fatty acids are combined with other nutrients, they’re more beneficial.

Other sources of omega-3 fatty acids

While flaxseed, chia seeds, walnuts, and canola oil also contain omega-3 fatty acids, these plant-based foods don’t provide as much omega-3 as fatty fish because they’re not as easily absorbed by the body.

Fibre

Fibre reduces the risk of constipation, which is common during pregnancy and is often caused by hormonal changes and iron supplements.

Eating fibre-rich foods every day and drinking plenty of water is essential to prevent or treat constipation. Consuming foods that are naturally high in fibre (such as those listed below) is more effective than eating foods that are enriched with concentrated fibre (such as oat fibre or inulin).

Iodine

Iodine is a mineral that’s present in very small quantities in our body. It helps us produce thyroid hormones, which are essential for bone formation, muscle contractions, heartbeats, and nutrient absorption. Iodine also contributes to fetal brain growth, and a deficiency may lead to developmental disorders.

Table salt sold in Canada has been combined with iodine for over 100 years. However, people are advised to use less salt nowadays, which has caused the population’s iodine intake to decline. Commercially processed foods—which are very salty—don’t contain iodine. The best solution is to cook at home as much as possible and add small pinches of salt here and there.

Choline

Choline is an essential nutrient involved in fetal brain development. It is believed to help prevent neural tube defects. It also helps the placenta function properly.

As choline is rarely included in prenatal supplements, pregnant women are advised to eat choline-rich foods regularly.

Vitamin B12

Vitamin B12 is essential for the production of red blood cells and the proper functioning of the baby’s nervous system. It works in conjunction with folic acid to make DNA (genetic material).

Since the vitamin is found almost exclusively in foods of animal origin, vegetarian women or those who eat very little meat, fish, eggs, or dairy products should pay special attention to their intake. It’s essential that they take a multivitamin that contains B12.

Vitamin B12 deficiency could impair a child’s cognitive functions and cause anemia. It may also impact the mother, causing memory impairment and other permanent neurological problems.

Vitamins and minerals

Vitamin C, B vitamins, zinc, magnesium, and several other vitamins and minerals also contribute to a healthy pregnancy. There is less mention of them because pregnant women who have a varied diet can easily get the necessary amounts. The nutrients we’ve talked about in this fact sheet can be more difficult to get from diet alone.

Things to keep in mind

• Taking a folic acid supplement is strongly advised for at least three months before conception.
• Taking a prenatal multivitamin is advised throughout pregnancy.
• A varied diet is essential to provide the pregnant woman and her baby with all the nutrients they need.

Scientific review: Stéphanie Côté, M.Sc., nutritionist Research and copywriting:The Naître et grandir team Updated: October 2019