If you are pregnant, or planning a pregnancy, you need to be careful about taking vitamins or any other type of supplements. Some can do more harm than good, so it's always best to check with your doctor before taking supplements.

What are vitamins and supplements?

Your body needs a variety of nutrients for good health: vitamins, minerals, protein, carbohydrates, fats and fibre.

Vitamins are organic compounds needed in small amounts that your body can't make for itself. Apart from vitamin D, which your skin makes from sunlight, most of the vitamins you need come from food.

Dietary supplements are complementary medicines which contain nutrients that may fill a deficiency (a gap) in your diet. Examples include multivitamins, single minerals, fish oil capsules and herbal supplements.

Essential vitamins and minerals in pregnancy

Good nutrition in pregnancy is vital for the healthy growth and development of your baby. You need to consume enough nutrients to meet your baby's needs, as well as your own.

When you're pregnant, you need more of some nutrients, including protein, folate, iodine, iron and some vitamins.

• folate (called 'folic acid' when in supplement form) helps prevent neural tube defects, such as spina bifida when taken at least 1 month before conception and throughout the first 3 months of pregnancy
• iodine is needed for brain and nervous system development
• iron helps prevent anaemia in the mother, as well as low birth weight in the baby

Vitamin B12 and vitamin D are also particularly important since they support the development of the baby's nervous system (B12) and skeleton (D). Adequate vitamin C intake also helps improve the adsorption of iron from your diet.

Do I need to take supplements?

It's recommended that all pregnant women in Australia take folic acid, iodine and vitamin D supplements.

Having a healthy diet is important and should provide you with the other nutrients you need. Check the Australian Dietary Guidelines for more advice. However, some pregnant women may need supplements of other nutrients besides folic acid, iodine and vitamin D.

If you have a known deficiency, your doctor might advise you to take a supplement. For example:

• if you are vegetarian or vegan and not getting enough vitamin B12
• if you don't get enough calcium, which is vital for bone health, from dairy or other calcium-rich foods
• if you are low in iron
• if you may be low in omega-3 fatty acids, e.g. if you eat very little seafood

If you're not sure whether you need a supplement, talk to your doctor.

Multivitamins in pregnancy

A multivitamin is a combination of different vitamins and minerals, usually taken as a tablet. Some multivitamins are designed especially for pregnant women (prenatal multivitamins). But they are not a substitute for a nutritious diet. It's important to eat healthily even if you're taking prenatal multivitamins.

If you're pregnant, avoid taking multivitamins that are not designed for pregnancy.

Take care with certain vitamins

Your body only needs a small amount of each nutrient, and higher amounts are not necessarily better. In fact, consuming more than you need can sometimes cause harm.

For example, high doses of vitamin A, vitamin C, or vitamin E can be dangerous. It's best not to take these vitamins as supplements in pregnancy.

It's also best to avoid foods that may be very high in vitamin A, including liver and liver products such as pâté.

Just as you need to check with your doctor before you take any medicines while pregnant, it's best to talk to your doctor before taking any supplements.

Other supplements in pregnancy

Other than folic acid, vitamin D and iodine and any supplement prescribed for you by your doctor, there is limited evidence to support the use of supplements during pregnancy.

Emerging research has shown that omega-3 supplements during pregnancy might help reduce the risk of premature birth, and that probiotics might help control blood glucose levels in pregnancy. But it's not clear whether the benefits of taking these supplements outweigh any possible harms. Until there is better evidence available, it's best to avoid them unless prescribed by your doctor — particularly in the first trimester of pregnancy.

Because nutritional supplements are classed as 'complementary medicines', they are not scrutinised or regulated as much as other medicines.

Resources and support

• Talk to your GP or midwife.
• Call 1300 MEDICINE on 1300 633 424 for advice about complementary medicines, Monday to Friday, 9am to 5pm AEST.
• Call Pregnancy, Birth and Baby on 1800 882 436 to speak with a maternal child health nurse (between 7am and midnight AEST).