How important is it to take a multi-vitamin throughout pregnancy?

Eating a healthy, varied diet in pregnancy will satisfy most of the vitamins and minerals you need. There are some vitamins and minerals that are especially important. It is recommended to get vitamins and minerals from the food you eat, but when you are pregnant you will need to take some supplements as well to make sure you get everything you need. It's recommended that you take:
10 micrograms of Vitamin D each day throughout your pregnancy and if you breastfeed
400 micrograms of folic acid each day – you should take this from before you are pregnant until you are 12 weeks pregnant .Do not take vitamin A supplements, or any supplements containing vitamin A (retinol), as too much could harm your baby.

You can get supplements from pharmacies and supermarkets, or your GP may be able to prescribe them for you. If you want to get your folic acid or vitamin D from a multivitamin tablet, make sure that the tablet does not contain vitamin A (or retinol).

Folic acid is important for pregnancy as it can help prevent birth defects known as neural tube defects, such as spina bifida. You should take a 400 microgram folic acid tablet every day while you are trying to get pregnant and until you are 12 weeks pregnant. If you didn't take folic acid before you conceived, you should start as soon as you find out that you are pregnant. You should also eat foods that contain folate (the natural form of folic acid), such as green leafy vegetables and brown rice. Some breakfast cereals, breads and margarines have folic acid added to them. Some women have an increased risk of having a pregnancy affected by a neural tube defect, and are advised to take a higher dose of 5 milligrams (5mg) of folic acid each day until they are 12 weeks pregnant. Women have an increased risk if they:
or their partner have a neural tube defect
have had a previous pregnancy affected by a neural tube defect
or their partner have a family history of neural tube defects
have diabetes
In addition, women who are taking anti-epileptic medication should consult their GP for advice, as they may also need to take a higher dose of folic acid.
If any of the above applies to you, talk to your GP as they can prescribe a higher dose of folic acid. Your GP or midwife may also recommend additional screening tests during your pregnancy.

Vitamin D regulates the amount of calcium and phosphate in the body, these are needed to keep bones and teeth healthy. You need to take vitamin D during your pregnancy to provide your baby with enough vitamin D for the first few months of its life. You should take a supplement of 10 micrograms of vitamin D each day when you are pregnant and if you breastfeed. In children, not having enough vitamin D can cause their bones to soften and can lead to rickets (a disease that affects bone development in children). Vitamin D can be found naturally in oily fish (such as salmon, mackerel and sardines), eggs and meat. Some manufacturers add it to some breakfast cereals, soya products, some dairy products, powdered milk, and fat spreads such as margarine. The best source of vitamin D is summer sunlight on your skin. The amount of time you need in the sun to make enough vitamin D is different for every person, and depends on things such as skin type, the time of day and the time of year. However, you don't need to sunbathe: the amount of sun you need to make enough vitamin D is less than the amount that causes tanning or burning. If you have dark skin or always cover your skin, you may be at particular risk of vitamin D deficiency. Talk to your midwife or doctor if this applies to you.

If you are short of iron, you’ll probably get very tired and may suffer from anaemia. Lean meat, green leafy vegetables, dried fruit, and nuts contain iron. If you'd like to eat peanuts or foods that contain peanuts (such as peanut butter) during pregnancy, you can do so as part of a healthy balanced diet unless you're allergic to them or your health professional advises you not to. Many breakfast cereals have iron added. If the iron level in your blood becomes low, your GP or midwife will advise you to take iron supplements.

I often recommend women see a naturopath in pregnancy so that an appropriate pregnancy supplement can be recommended.  This is particularly so in cases as you have a described where you are feeling sick.  Naturopathic supplements may be more digestible and more easily absorbed.

You actually don't need a ‘perfect’ diet to grow and feed a baby, but obviously it is better to eat a diet close to the dietary guidelines.

In actual fact, there is only one nutrient that is really essential to have as a supplement during pregnancy and breastfeeding, that the mother cannot get enough of from the diet in Australia, no matter how good it is, and that is iodine.

Iodine is very important for your baby's brain development. The NHMRC have a statement available at http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/new45_statement.pdf that explains the need for an iodine supplement. Women should take a supplement containing 150 ug/day. This is available in any pregnancy and breastfeeding multivitamin and also in a separate supplement containing only folate and iodine, for those who don't want a full multivitamin.

The only supplements that are routinely recommended in pregnancy are folate and iodine. As it can be difficult to get the amounts needed for pregnancy from food alone the NRMRC recommend that all pregnant women take them in supplement form in addition to eating foods rich in these nutrients.

If you have low levels of vitamin D then you will need a supplement to boost your intake and if you don’t eat fish then taking a fish oil or vegetarian DHA supplement will help to ensure you have enough of these important fats while you are pregnant.  Some women will also need an iron supplement if they are unable to maintain adequate iron levels from diet alone.
 
While studies have shown that taking multivitamin and mineral supplement containing folate can reduce the risk of birth defects, folate alone reduces the risk so if you eat a healthy well-balanced diet just supplementing with folate and iodine is likely to be sufficient.  If you do supplement, it is important that you don’t take large amount of any vitamins or minerals that may be unsafe in pregnancy (for example, Vitamin A).  The best option is a specially formulated pregnancy multivitamin and mineral preparation which contains a balanced amount of the vitamins and minerals needed in pregnancy including those above, without anything you shouldn’t be taking.  These supplements vary in their content so it is best to check with your doctor, midwife or dietitian about which is the best option for you.

In addition to the answers above, you might also be interested to take a look at the reccomended dietay guidelines of eating during pregnancy by the NHMRC (National Health Medical Research Council).

https://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/n55h_healthy_eating_during_pregnancy.pdf

https://www.nhmrc.gov.au/guidelines/publications/n55 (scoll down and select handout  on ‘healthy eating during pregnancy’)