Almost all pregnant women take some sort of complementary and alternative medicine (CAM) supplements; surveys show that about 90% of pregnant women are using them. CAM includes vitamin and mineral supplements, and it’s recommended all pregnant women take folic acid and iodine supplements, so this high level of use isn’t surprising - although about 10% appear not to take these important nutrients, which is a concern.
Roughly half of pregnant Australian women take CAM supplements, according to a recent large survey; over a third take herbal medicines, with flower essences, aromatherapy oils, and homeopathic products also being used.
However, the widespread perception that these products are 'natural', and therefore safe, is misguided. Some herbs are capable of causing adverse pregnancy outcomes (such as miscarriage, or preterm labour) and birth defects – see Herbal medicines in pregnancy for more on this.
In this article, we look at supplements that are recommended for or commonly used during pregnancy. We also wanted to find out what advice pregnant women are given in pharmacies and health food shops where pregnancy supplements are frequently purchased.
Vitamins and minerals important for pregnancy
While a healthy diet is generally sufficient to ensure pregnant women get adequate vitamins and minerals for themselves and the developing foetus, there are two supplements recommended for all pregnant women: folic acid and iodine.
The recommended intake of folic acid for pregnant women is 600mcg per day, with a supplement of at least 400mcg recommended one month before conception and three months after to help prevent neural tube defects. All pregnancy multivitamin supplements contain at least this.
Iodine deficiency is quite common, but iodine is critical for a baby's brain development. Because most foods are low in this important element, we need to get iodine from fortified foods and/or supplements. Iodised salt is one option, although many people have cut down on added salt, or switched to (non-iodised) gourmet salt. While it’s now used in bread manufacturing, this isn’t enough to ensure pregnant and lactating women are getting enough iodine. A 150mcg supplement is recommended.
While some sources claim fish oil is critical for the development of the brain and eyes of the baby, others are more cautious and say there’s no conclusive evidence that this is the case. There is, however, growing evidence that fish oil supplements may help prevent very early labour. At present, the Royal Australian and New Zealand College of Obstetricians and Gynaecologists doesn’t include fish oil in its recommendations.
Other vitamins and minerals for which supplements may be necessary in some cases include calcium (for people who limit or avoid dairy products), vitamin B12 (for vegans and possibly some vegetarians), iron (for women with low haemoglobin levels) and vitamin D (women who avoid sun, or are dark-skinned or obese, may be deficient).
Advice from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists is that vitamin and mineral supplements (with the exception of iodine and folic acid) are generally only recommended in specific situations where a deficiency has been identified or is likely.
Handle with care
For some important vitamins, more isn’t better.
Vitamin A comes in two forms: pre-formed vitamin A (found in meat, especially liver) and beta-carotene (from plants). It can be toxic at high levels, and pregnant women should keep their intake of pre-formed vitamin A below 10,000 IU or 3000mcg. Pregnancy vitamin supplements usually contain the safer beta-carotene form of vitamin A, if they contain it at all. But other (non-pregnancy) multivitamins may contain only pre-formed vitamin A (typically retinyl palmitate) or a mixture of beta-carotene and pre-formed vitamin A, so check the label.
High-dose vitamin B6 may be recommended to help relieve nausea and vomiting of pregnancy, and some morning sickness preparations have doses of up to 75mg per day. While the recommended daily intake is only 1.9mg, the upper level of recommended intake for pregnant women is 50mg, so some morning sickness preparations are above this upper level.
Furthermore, some pregnancy multivitamins contain 50mg – so if you’re taking a pregnancy multi as well as vitamin B6 in a morning sickness product, doubling up on potentially harmful high doses is a possibility. More than 100mg per day in the first trimester may be linked to birth defects involving the baby's arms, legs, and nerve development.
While herbal medicines are often perceived to be natural and safe, there’s little information about the safety and effectiveness of such products in pregnancy, and many women taking them don’t tell their doctor.
But 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 stretchmarks 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 taking caution with, the following herbal medicines:
- Aloe vera While OK as a topical gel, 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 Limited safety information.
- Fenugreek While OK to use in normal quantities in cooking, 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 1 to 2g 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 events.
- 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 labour, although there’s little evidence to support this, nor is there much information about its safety. Avoid in early pregnancy.
- Spirulina Little is known about its safety during pregnancy, so it’s best to avoid it or seek advice from your doctor.
- St John's Wort may reduce birthweight, and interferes with certain medicines. Talk to your doctor before taking it while pregnant.
- Valerian There’s a lack of safety information about taking it in pregnancy. Talk to your doctor first.