Until recently, the main supplements recommended for pregnancy were folic acid and iron. Increased blood volume and the developing placenta place large demands on iron stores, and maternal folic acid (ideally taken before conception) helps prevent spina bifida and other neural tube defects.

These days though, there are any number of specialist multivitamin and mineral preparations designed for pregnancy and breastfeeding, as well as conception. But is there any evidence that they're beneficial?

Micronutrient requirements of pregnant women

The National Health and Medical Research Council (NHMRC) lists recommended daily intakes of various nutrients for pregnant and breastfeeding women based on the latest available evidence. The key nutrients for pregnant women are as follows:

Iron

Pregnancy increases the need for iron in the diet. Apart from increased vascular blood mass for the mother and placenta, the developing foetus draws iron from the mother for use in the first five or six months after birth too. Although studies show that absorption of iron can increase substantially during pregnancy, the recommended daily intake (RDI) is set at 27mg, and vegetarians, vegans and women carrying more than one baby are at risk of iron deficiency. But too much iron also presents its own problems.

Folic acid

The RDI for women is 600 micrograms (mcg) for one month before conception and for three months after. In 2009, Food Standards mandated that bread be fortified with folic acid, and two slices contain about 80mcg. This will help, but a supplement is still recommended, as are natural sources such as green vegetables and wholegrains. The general recommendation is that in addition to eating folate-rich foods, women planning a pregnancy or in their first trimester should take a daily supplement containing at least 400mcg (preferably 500mcg) of folic acid.

Iodine

Iodine is necessary for the normal growth and mental development of a baby, and the RDI for pregnant women is 220mcg and 270mcg for breastfeeding women. After milk producers switched from using iodine-based to chlorine-based cleaners to clean dairy equipment, and more people ditched iodised table salt for gourmet salt – or none at all – iodine deficiency became an issue, with pregnant woman in parts of Australia suffering mild to moderate deficiency in the early 2000s.

Since 2009, bread manufacturers have been required to use iodised salt in all bread except organic bread. This is expected to increase average iodine levels by about 54mcg per day. However, on its own this won't ensure pregnant or lactating women are getting enough iodine, and a 150mcg supplement is recommended. The NHMRC recommends you avoid kelp and kelp-derived iodine due to mercury poisoning risks.

Vitamin D

Vitamin D helps the body absorb and use calcium. The most recent recommendations are that an adequate intake (AI) for all adults up to the age of 70, including pregnant and lactating women, is 15mcg (or 600 international units) of dietary vitamin D per day. While we can get our vitamin D from the sun, deficiency is an emerging health issue in Australia. Studies of the general population show that although few people are moderately or severely deficient in vitamin D, a significant number (23–49%) have a mild deficiency.

The main risks for deficiency are having dark skin and covering up for religious or cultural reasons. People living in colder southern parts of Australia are also susceptible to deficiency. Obesity is another risk factor, and a Queensland study found 14% of pregnant women were obese.

Most people will get enough vitamin D by spending 10 minutes in the morning or late afternoon sun with face, arms and hands exposed; this should be a bit longer in winter though (15 minutes generally, or 30 minutes in Tasmania).

The level of vitamin D in pregnancy supplements may be less than the recommended adequate intake of 600 IU. So if you're at increased risk of deficiency, consult your doctor for advice.

Calcium

A developing foetus needs calcium for healthy bones, teeth, muscles, nerves and their heart. Normal levels of recommended calcium intake will suffice, although pregnant teenagers will need extra. For most people, calcium needs can be met through the diet. Women who avoid dairy products or have a vitamin D deficiency may need a supplement.

Vitamin B12

Vitamin B12 is needed for neurodevelopment. It's only found in animal products (meat, eggs and dairy) and some types of algae, so vegans may need vitamin B12 daily supplementation of 250-500mcg.

Omega 3 fatty acids

Many supplements contain fish oil, which provides omega-3 fatty acids essential for the baby's neural development. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists currently don't recommend it in the first trimester, due to a lack of evidence supporting its use and a lack of safety data. But they told us that this position is likely to change soon, with more evidence of its safety now available.

Supplements for morning sickness

Morning sickness affects between 50-80% of women in early pregnancy. Advice for treating it includes eating dry foods, having small, frequent snacks, and avoiding food or situations that cause nausea.

Vitamin B6 and ginger are often recommended to help relieve nausea and vomiting. A large review of studies found that these may help relieve the nausea, but not necessarily the vomiting associated with morning sickness, but the evidence was limited and inconsistent, with some studies finding no effect. Furthermore, too much B6 or ginger can be unsafe.

Other herbal supplements commonly used by women for morning sickness relief include peppermint, chamomile, and raspberry leaf, with acupressure and homeopathy among other alternative therapies used, but there isn't any reliable evidence available that they're effective.

Be careful taking products containing ginger for travel sickness, as the packaging may not include dosing instructions for pregnancy or a warning about excessive intake in pregnancy. In some cases, if the maximum dose on the package is followed, it would exceed the presumed safe level of 100 milligrams of ginger per day in pregnancy.

Too much of a good thing?

Taking some vitamins in excess can cause problems though, so keep an eye on your intake and be careful not to overdo it. These include:

Vitamin A

Vitamin A is available as retinol or from conversion of beta carotene in brightly coloured fruits and vegetables. The retinol form is found in liver, full-fat dairy products and margarines. The particularly high levels in liver can be toxic, and pregnant women are advised to avoid liver and paté for this reason. Vitamin pills tend to contain the beta carotene form of vitamin A. Avoid those containing retinol.

Vitamin B6

Vitamin B6 may help relieve nausea associated with morning sickness. Many supplements contain 50mg of vitamin B6, which is much greater than the RDI of 1.9mg/day, but is at the upper level of recommended intake for pregnant women. A typical balanced diet will give you a few milligrams in addition to this, but it's extremely unlikely you'd get anywhere near the safe maximum of 100mg per day without additional supplements. More than 100mg per day in the first trimester may be linked to birth defects involving the baby's arms, legs and nerve development.

Iron

The RDI for iron is 27mg for pregnant women. The upper intake for iron from all sources is 45mg per day, and most supplements have less than this. At higher levels, there is a risk of gastrointestinal upset and constipation, though this can be minimised by taking the pill with food and drinking plenty of water throughout the day. In cases of iron-deficiency anaemia, it's essential to have a doctor supervise the intake of iron, as too much iron can lead to an excessive increase in red blood cells (called haemoconcentration), which thickens blood and slows its flow, causing, paradoxically, the same problems in foetuses as too little iron: premature birth and low birth weight. Iron supplements are also hazardous for the 1 in 300 people with haemochromatosis, a condition that may not be diagnosed in women during their child-bearing years.

Do you need a special supplement?

Clinical trials have shown the benefit of taking vitamins and mineral supplements designed for pregnancy, but almost all have been conducted in low- or middle-income countries where malnutrition is common. The main benefits reported are reduced risk of neural tube defects and maternal anaemia. Where there's a risk of malnutrition, supplements have been shown to reduce the risk of low-birth-weight babies.

If your diet is generally healthy, with plenty of fruit, vegetables, nuts, pulses and dairy products (or calcium-fortified alternatives), you're unlikely to benefit from a pregnancy supplement. There are lots of nutritional benefits from food that can't be obtained from a vitamin pill – and no pill will undo the negatives of a diet of pies, chips and chocolate.

The reality, however, is that many women – pregnant or not – don't have a diet that's entirely healthy, and some women struggle to eat well if they suffer severe morning sickness, in which case the extra nutrients in pregnancy supplements may be useful.

RANZCOG states that "although, in the general population, a healthy balanced diet should largely obviate the need for vitamin and mineral supplementation, pregnancy and lactation create extra nutritional demands that, for some individuals, may make supplementation advisable."

The college recommends supplements in the following situations, in consultation with your doctor:

  • Iodine and folic acid supplementation for all pregnant women.
  • Additional folic acid (5mg per day) for women with a multiple pregnancy, taking anti-convulsants, people with diabetes and those who have a tendency toward blood clotting or a family history of neural tube defects.
  • Vitamin B12 for vegetarians and vegans.
  • Iron for vegetarians and vegans, and women with a multiple pregnancy.
  • Calcium for people who avoid dairy (e.g. lactose-intolerant or vegan).
  • Vitamin D may be necessary for people at risk of deficiency.

"Pregnancy multivitamins won't cause any harm, and may confer some benefit for women who don't have a healthy diet," says Dr Louise Farrell, Chair of RANZCOG's Women's Health Committee. She points out that maternal micronutrient supplementation and foetal health is a developing science and under continual review.

Herbal medicines in pregnancy

Herbal medicines are often perceived to be natural and safe, but there's not much information about the safety and effectiveness of these products in pregnancy, and many women taking them don't tell their doctor.

There's very real cause for concern, with numerous studies linking herbal medicines with adverse effects in pregnancy. For example, a large study found that using almond oil to prevent stretch marks was linked with increased risk of premature birth, while chamomile and liquorice may be linked to threatened miscarriage and premature birth. Common Chinese herbal medicines, especially when taken in early pregnancy, have been linked with growth and developmental abnormalities in baby mice, and some have also been linked with human abnormalities.

The Royal Women's Hospital in Melbourne recommends avoiding, or exercising caution with, the following herbal medicines:

  • Aloe vera is OK as a topical gel, but aloe vera latex taken orally in powder or liquid form may cause low blood sugar, uterine contractions, or miscarriage. There's not enough information about safe doses in pregnancy, so it's probably best to avoid aloe vera juice and supplements.
  • Black cohosh may cause early labour, so avoid in early pregnancy.
  • Evening primrose oil has limited safety information.
  • Fenugreek is OK to use in normal quantities in cooking, but the larger quantities found in supplements may cause miscarriage or early labour.
  • Garlic as used in a cooking is fine, but avoid large doses in supplements, as they may cause bleeding, miscarriage or early labour.
  • Ginger is OK in cooking and in supplement doses of up to 100mg per day. Large doses can cause thinning of the blood and heartburn.
  • Ginseng should be avoided during pregnancy, especially early pregnancy, as it can cause serious adverse reactions.
  • Liquorice in large quantities, as in liquorice extract or liquorice root, can cause miscarriage and early labour. Black liquorice sold as confectionery may contain the extract, or may be flavoured with aniseed.
  • Raspberry leaf is said to help reduce the length of labour, although there's little evidence to support this and there isn't much information about its safety. Avoid in early pregnancy.
  • Spirulina has little information about its safety during pregnancy, so it's best to avoid it or seek advice from your doctor.
  • St John's Wort may reduce your baby's birth weight, and interferes with certain medicines. Talk to your doctor before taking it while pregnant.
  • Valerian has limited safety information about taking it in pregnancy. Talk to your doctor first.

Breastfeeding

After bub's arrived, you won't need extra nutrients such as iron, but you'll need more of some other nutrients, including vitamins A, all the B complex vitamins, C and E, and most especially iodine. A healthy diet and increased appetite should ensure adequate levels of most of these nutrients, although an iodine supplement may be necessary.

What about conception?

There are several micronutrient formulations available for women and men trying to conceive.

For women, a folic acid supplement is recommended for one month prior to conception to reduce risks of neural tube defects. There's no need for any other special supplement at this stage, although if your diet isn't as healthy and balanced as it should be, now's the time to start good habits to see you through pregnancy and family life.

For men, small studies with low numbers of live births suggest that antioxidants create healthier sperm, and men with low fertility have been found to have lower levels of antioxidants in semen than fertile men. Antioxidant supplements containing vitamins and minerals, such as vitamin E, vitamin C, carotenoids, ubiquinol, folate and zinc are promoted to men for increasing the chances of conception. There's some evidence they can help, but it's based on only a few studies and further work is needed to confirm the findings.

Humans produce their own antioxidants and also get some from plant foods, especially fruit and vegetables. Other contributors to poor sperm health include excessive exercise, alcohol, smoking, drugs, stress and environmental pollution, so this might be the time to spring clean your lifestyle!

CHOICE verdict

In short, if you have a healthy diet you'll need just iodine and folic acid supplements during pregnancy. Depending on your diet and other circumstances, a pregnancy multivitamin might be useful, but choose it based on your needs and on price.

We looked at the ingredients of various pregnancy and breastfeeding formulations. All contained the recommended intake of folic acid and iodine, which many regular multivitamins don't have. Many contained unnecessary vitamins and minerals too, or pointlessly low levels of nutrients, particularly calcium. If you're only after the iodine and folic acid, get a supplement that contains only these nutrients and save money.

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