While there is evidence to support routine supplementation with folic acid and iodine in pregnancy, other vitamin and mineral supplements are not of benefit unless there is an identified deficiency. The evidence on complementary therapies in pregnancy is limited.
10.4.1 Folic acidFolic acid supplementation prevents first and second time occurrence of neural tube defects (De-Regil et al 2010). In Australia, the rates of abnormalities such as encephalocele, anencephaly and spina bifida have fallen with promotion of folic acid supplements and voluntary fortification (Bower et al 2009). However, no such falls have been seen for Aboriginal babies (Bower et al 2009) and the prevalence of neural tube defects among Aboriginal and Torres Strait Islander babies is almost double that in the non-Indigenous
population (Bower et al 2004). Levels of knowledge about folic acid supplementation appear to be lower among Aboriginal and Torres Strait Islander women (55% vs 67.5% of the mostly non-Indigenous women surveyed), particularly among adolescent women (38%) (Bower et al 2004). Restricted food choices and higher costs in rural and remote areas may also contribute to lower levels of folate intake and higher prevalence of neural tube defects (Bower et al 2004).
Women taking medicines that are folate antagonists (eg carbamazepine, lamotrigine) should be encouraged to take high-dose folate supplements preconception and during the first trimester (beyondblue 2011).
Recommendation Grade A26. Inform women that dietary supplementation with folic acid, from 12 weeks before conception and throughout the first 12 weeks of pregnancy, reduces the risk of having a baby with a neural tube defect and recommend a dose of 500 micrograms per day.
Practice pointgg. Specific attention needs to be given to promoting folic acid supplementation to Aboriginal and Torres Strait Islander women of childbearing age and providing information to individual women at the first antenatal visit.
10.4.2 Other vitaminsStudies into the effects of supplementation during pregnancy of vitamin C (Rumbold & Crowther 2005), combined vitamins C and E (Xu et al 2010) and vitamin A (Kirkwood et al 2010; van den Broek et al 2010) have found no benefit. However, supplementation has been associated with:
- preterm birth (vitamin C) (Rumbold & Crowther 2005);
- perinatal death and preterm rupture of the membranes (vitamins C and E) (Xu et al 2010); and
- congenital malformation (vitamin A)(Oakley & Erickson 1995; Rothman et al 1995; Dolk et al 1999).
- There is insufficient evidence about the effects of other combinations of vitamins on pregnancy outcomes (Rumbold et al 2011).
Recommendation - Grade B27. Advise women that taking vitamins A, C or E supplements is not of benefit in pregnancy and may cause harm.
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10.4.3 Iodine1Increased thyroid activity during pregnancy increases iodine requirements. If iodine intake is inadequate before pregnancy, maternal stores may run low and be inadequate to support the unborn baby in later stages of pregnancy (Smyth 2006). Iodine deficiency is of particular concern during pregnancy because abnormal function of the mother’s thyroid has a negative impact on the nervous system of the unborn baby, and increases the risk of infant mortality (Zimmerman 2009). Adverse effects on early brain and
nervous system development are generally irreversible and can have serious implications for mental capacity in later life (WHO 2005–09).
There are limited studies specific to the iodine status of pregnant women in Australia, but those available prior to fortification suggest it was inadequate (APHDPC 2007). With the introduction of mandatory iodine fortification of bread, most of the Australian population will get enough iodine (Food Standards Australia New Zealand 2008) and women of child-bearing age should enter pregnancy with adequate iodine intake. However, the extra iodine available through fortified bread is not enough to meet the additional needs of pregnancy and during breastfeeding (Burgess et al 2007).
Consensus-based recommendationxiv Advise women who are pregnant to take an iodine supplement of 150 micrograms each day. Women with pre-existing thyroid conditions should seek advice from their medical practitioner before taking a supplement.
10.4.4 Iron supplementationThere is a lack of evidence that, in otherwise healthy women, the benefits of treatments for mild irondeficiency anaemia in pregnancy will outweigh the adverse effects associated with them (Reveiz et al 2007). There is a potential dose response relationship between dose of iron and reported adverse events (Reveiz et al 2007).
Women can be advised to consume iron-rich foods and that vitamin C (eg in fruit juice) aids absorption while tea and, to a lesser degree, coffee reduce the amount of iron available for absorption (NHMRC 2005).
Recommendation - Grade B28. Do not routinely offer iron supplementation to women during pregnancy.
10.4.5 Practice summary — advising women about nutritional supplementsWhen — At antenatal visits
Who — Midwife; GP; obstetrician; Aboriginal and Torres Strait Islander health worker; multicultural health worker; pharmacist
- Discuss use of nutritional supplements with women — Explain that some supplements (folic acid, iodine) are recommended for all women during pregnancy, while others (vitamins A, C and E and iron) are not of benefit and may be harmful and that iron should only be supplemented if a deficiency is identified.
10.4.6 ResourcesNHMRC (2010) NHMRC Public Statement: Iodine Supplementation for Pregnant and Breastfeeding Women. Canberra: National Health and Medical Research Council. For more information please visit National Health and Medical Research Council website.
FSANZ (undated) Thinking About Having a Baby? Important Things You Need to Know About What You Eat and Drink. Food Standards Australia and New Zealand. www.foodstandards.gov.au/_srcfiles/FSANZ%20Pregnancy_WEB.pdf (This website link was valid at the time of submission).
National Health and Medical Research Council (2013) Australian Dietry Guidelines. Canberra: National Health and Medical Research Council.
NHMRC (2005) Nutrient Reference Values for Australia and New Zealand. Canberra: National Health and Medical Research Council. For more information please visit National Health and Medical Research Council website.
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10.4.7. ReferencesAPHDPC (2007) The Prevalence and Severity of Iodine Deficiency in Australia. Australian Population Health Development Principal Committee. Report Commissioned by the Australian Health Ministers’ Advisory Committee.
beyondblue (2011) Clinical Practice Guidelines for Depression and Related Disorders — Anxiety, Bipolar Disorder and Puerperal Psychosis — in the Perinatal Period. A Guideline for Primary Care Health Professionals. Melbourne: beyondblue: the national depression initiative.
Bower C, D’Antoine H, Stanley FJ (2009) Neural tube defects in Australia: Trends in encephaloceles and other neural tube defects before and after promotion of folic acid supplementation and voluntary food fortification. Birth Defects Res A Clin Mol Teratol 85(4): 269–73.
Bower C, Eades S, Payne J et al (2004) Trends in neural tube defects in Western Australia in Indigenous and non-Indigenous populations. Paediatr Perinatal Epidemiol 18(4): 277–80.
Burgess JR, Seal JA, Stilwell GM et al (2007) A case for universal salt iodisation to correct iodine deficiency in pregnancy: another salutary lesson from Tasmania. Med J Aust 186: 574–76.
De-Regil LM, Fernández-Gaxiola AC, Dowswell T et al (2010) Effects and safety of periconceptional folate supplementation for preventing birth defects. Cochrane Database of Systematic Reviews DOI: 10.1002/14651858. CD007950.pub2.
Dolk HM, Nau H, Hummler H et al (1999) Dietary vitamin A and teratogenic risk: European Teratology Society discussion paper. Eur J Obstet Gynecol Reprod Biol 83: 31–6.
Food Standards Australia New Zealand (2008) Approval Report Proposal P1003 – Mandatory Iodine Fortification for Australia. Commonwealth of Australia. Available online at Food Standard Australia New Zealand website.
Kirkwood BR, Hurt L, Amenga-Etego S et al (2010) Effect of vitamin A supplementation in women of reproductive age on maternal survival in Ghana (ObaapaVitA): a cluster-randomised, placebo-controlled trial. Lancet 375(9726): 1640–49.
NHMRC (2005) Nutrient Reference Values for Australia and New Zealand. Canberra: National Health and Medical Research Council. Please visit National Health and Medical Research Council website.
Oakley GP Jr & Erickson JD (1995) Vitamin A and birth defects. Continuing caution is needed. New Engl J Med 333: 1414–15.
Reveiz L, Gyte GM, Cuervo LG (2007) Treatments for iron-deficiency anaemia in pregnancy. Cochrane Database of Systematic Reviews DOI: 10.1002/14651858.CD003094.pub2.
Rothman KJ, Moore LL, Singer MR et al (1995) Teratogenicity of high vitamin A intake. New Engl J Med 333: 1369–73.
Rumbold A & Crowther CA (2005) Vitamin C supplementation in pregnancy. Cochrane Database of Systematic Reviews DOI: 10.1002/14651858.CD004072.pub2.
Rumbold A, Middleton P, Pan N et al (2011) Vitamin supplementation for preventing miscarriage. Cochrane Database of Systematic Reviews DOI: 10.1002/14651858.CD004073.pub3.
Smyth PP (2006) Dietary iodine intakes in pregnancy. Irish Med J 99(4): 103.
van den Broek N, Dou L, Othman M et al (2010) Vitamin A supplementation during pregnancy for maternal and newborn outcomes. Cochrane Database of Systematic Reviews DOI: 10.1002/14651858.CD008666.pub2.
WHO (2005–09) Micronutrient Deficiencies. World health Organization Regional Office for the Western Pacific. For more information please visit World Health Organisation Western Pacific Region website.
Xu H, Perez-Cuevas R, Xiong X et al (2010) An international trial of antioxidants in the prevention of preeclampsia (INTAPP). Am J Obstet Gynecol 239.e231–39.e210.
Zimmermann MB (2009) Iodine deficiency in pregnancy and the effects of maternal iodine supplementation on the offspring: a review. Am J Clin Nutr 89: 668S–72S.
1 This section, including the consensus-based recommendation, is based on NHMRC (2010) NHMRC Public Statement: Iodine Supplementation for Pregnant and Breastfeeding Women. Canberra: National Health and Medical Research Council.