Iron is an essential mineral necessary for transport of oxygen, as well as the production of hemoglobin and enzymes involved in many body functions. Physiologic iron requirements are 3 times greater in pregnant than in menstruating women.26 The increased need for iron in pregnancy is related to the growing placenta and fetus, and the expansion of blood volume by 50% increases demands for iron from 1.0 mg/dL at conception to 5.0 mg/dL by the second and third trimesters.27,28 The US Centers for Disease Control and Prevention defines anemia in pregnancy as hemoglobin concentration <11.0 g/dL in the first and third trimesters and <10.5 g/dL in the second trimester. An estimated 38% of pregnant women worldwide are anemic; in the United States, nearly 18% of pregnant women are anemic.28,29
In addition to the risk for anemia due to increased demand in pregnancy, the most common cause of iron deficiency is malnutrition, notably in those living in poverty or those consuming vegan or iron-poor diets. Other contributors include gastrointestinal absorption deficiencies and chronic blood loss.30
Iron supply in food comes in 2 forms: heme and nonheme. Heme iron is highly bioavailable (15%-35%) and is found primarily in animal foods, including chicken liver, oysters, clams, beef liver, beef, tuna, eggs, shrimp, and lamb.26 Nonheme iron is found in nonanimal food and in iron-fortified foods, and has low bioavailability (2%-20%). Nonheme iron foods include bran, instant oatmeal, beans, molasses, spinach, brown rice, and peanut butter.
Symptoms of iron deficiency are often attributed to symptoms of pregnancy; however, iron deficiency may be the source of some of these symptoms, including fatigue, tachycardia, lightheaded and dizzy feelings, shortness of breath, and restless legs.31 In pregnancy, symptoms of anemia are also associated with preterm labor, low birthweight, and newborn and maternal mortality.30
Recommendation: Adequate but not too much is the goal with iron; the upper limit of iron intake is 45 mg/d.32 Women of childbearing age benefit from supplementation of 18 mg/d of iron, with adjustments based on dietary habits and menstrual losses. Pregnant women may require 30 to 40 mg to meet metabolic iron requirements.33 Although iron obtained via dietary intake is not likely to meet the demand of pregnant women, a diet that is iron abundant and highly bioavailable is recommended. Ascorbic acid may support the absorption of iron; foods that inhibit iron absorption include milk, coffee, and black tea. Iron supplementation at bedtime or between meals may also enhance its absorption.34
Because primary care providers lay the foundation of health for future pregnancies, their guidance in preparing women for healthy pregnancies is essential. A large part of this includes understanding the potential effects of micronutrients on pregnancy outcomes. Women of childbearing age may benefit from some supplementation. Discussion with women regarding their plans for pregnancy, diet, and lifestyle will help practitioners determine how to best direct patients in their decision to supplement with micronutrients.
Jodi Westfall, FNP-C, DCNP, PMH-NP-C, is an integrative medicine and nutrition specialist, and Jennifer Rode, PhD, ANP-C, is an associate professor in the Department of Nursing at Miami University in Hamilton, Ohio.
- Wu G, Imhoff-Kunsch B, Girard AW. Biological mechanisms for nutritional regulation of maternal and fetal development. Paediatr Perinatal Epidemiol. 2012;26(suppl 1):4-26.
- Finer LB, Zolna MR. Shifts in intended and unintended pregnancies in the United States, 2001–2008. Am J Public Health. 2014;104:(suppl 1):S43-S48.
- Dunlop AL, Jack B, Frey K. National recommendations for preconception care: the essential role of the family physician. J Am Board Fam Med. 2007;20(1):81-84.
- Cetin I, Berti C, Calabrese S. Role of micronutrients in the periconception period. Hum Reprod Update. 2010; 16(1):80-95.
- Pietrzik K, Bailey L, Shane B. Folic acid and l-5-methyltetrahydrofolate: comparison of clinical pharmacokinetics and pharmacodynamics. Clin Pharmacokinet. 2010;49(8):535-548.
- Nazki FH, Sameer AS, Ganaie BA. Folate: metabolism, genes, polymorphisms and the associated diseases. Gene. 2014;533(1):11-20.
- Yan L, Zhao L, Long Y, et al. Association of the maternal MTHFR C677T polymorphism with susceptibility to neural tube defects in offsprings: evidence from 25 care-control studies. PLoS One. 2012;7(10):e41689.
- Zhang T, Lou J, Zhong R, et al. Genetic variants in the folate pathway and the risk of neural tube defects: a meta-analysis of the published literature. PLoS One. 2013;8(4):e595570.
- Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline. Dietary Reference Intakes for Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
- Lamers Y, Prinz-Langenohol R, Moser R, Pietrzik K. Supplementation with [6S]-5-methyltetrahydrofolate or folic acid equally reduces plasma homocysteine concentrations in health women. Am J Clin Nutr. 2004;79(3):473-478.
- Caron P. Neurocognitive outcomes of children secondary to mild iodine deficiency in pregnancy women. Ann Endocrinol (Paris). 2015;76(3):248-252.
- Román GC, Ghassabian A, Bongers-Schokking JJ, et al. Association of gestational maternal hypothyroxinemia and increased autism risk. Ann Neurol. 2013;74(5):733-742.
- World Health Organization. Assessment of Iodine Deficiency Disorders and Monitoring Their Elimination. A Guide for Programme Managers. 3rd ed. Geneva, Switzerland: World Health Organization; 2007.
- Caldwell KL, Pan Y, Mortensen ME, Makhmudov A, Merrill L, Move J. Iodine status in pregnant women in the National Children’s Study and in US women (15-44 years), National Health and Nutrition Examination Survey 2005-2010. Thyroid. 2013;23(8):927-937.
- Institute of Medicine. Sodium Intake in Populations. Assessment of Evidence. Washington, DC: The National Academies Press; 2013.
- Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. Washington, DC: The National Academies Press; 1997.
- James MF. Magnesium in obstetrics. Best Pract Res Clin Obstet Gynaecol. 2009;24(3):327-337.
- Jahnen-Dechent W, Ketteler M. Magnesium basics. Clin Kidney J. 2012;5(suppl 1):i3-i14.
- Rosanoff A, Weaver CM, Rude RK. Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutr Rev. 2012;70(3):153-164.
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Res. 2001;14(4):257-262.
- Lappe JM. The role of vitamin D in human health: a paradigm shift. J Evid Based Integr Med. 2011;16(1):58-72.
- Forrest KY, Stuhldreher WL. Prevalence and correlated of vitamin D deficiency in US adults. Nutr Res. 2011;31(1):48-54.
- Kennel KA, Drake MT, Hurley DL. Vitamin D deficiency in adults: when to test and how to treat. Mayo Clin Proc. 2010;85(8):752-758.
- Aghajafari F, Nagulesapillai T, Ronksley PE, Trough SC, O’Beirne M, Rabi DM. Association between serum maternal 25-hydroxyvitamin D level and pregnancy and neonatal outcomes: systemic review and meta-analysis of observational studies. BMJ. 2013;346:f1169.
- Hollis BJ, Johnson D, Hulsey TC, Ebeling M, Wagner CL. Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness. J Bone Miner Res. 2011;26(10):2341-2357.
- Abbaspour N, Hurrell R, Kelishadi R. Review on iron and its importance for human health. J Res Med Sci. 2014;19(2):164-174.
- Aranda N, Ribot B, Garcia E, Viteri FE, Arija V. Pre-pregnancy iron reserves, iron supplementation during pregnancy, and birth weight. Early Hum Dev. 2011;87(12):791-797.
- Mei Z, Cogswell ME, Looker AC, et al. Assessment of iron status in US pregnant women from the National Health and Nutrition Examination Survey (NHANES), 1999-2006. Am J Clin Nutr. 2011;93(6):1312-1320.
- Stevens GA, Finucane MM, De-Regil LM, et al; Nutrition Impact Model Study Group (Anaemia). Global, regional and national trends in haemoglobin concentration and prevalence of total and severe anaemia in children and pregnant and non-pregnant women for 1995-2011: a systematic analysis of population-representative data. Lancet Glob Health. 2013;1(1):e16-e25.
- Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;373(5):485-486.
- Miller JL. Iron deficiency anemia: a common and curable disease. Cold Spring Harb Perspect Med. 2013;3(7). pii: a011866. doi: 10.1101/cshperspect.a011866
- Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: The National Academies Press; 2001.
- Milman N. Oral iron prophylaxis in pregnancy: not too little and not too much! J Pregnancy. 2012;2112:514345.
- Milman N. Iron prophylaxis in pregnancy – general or individual and in which dose? Ann Hematol. 2006;85(12):821-828.
- American College of Obstetricians and Gynecologists. Vitamin D: screening and supplementation during pregnancy. Committee Opinion. 2011; No. 495(118):197-198.
- National Institutes of Health Office of Dietary Supplements. Iron. Available at: https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/. Accessed October 1, 2018.
- Centers for Disease Control and Prevention. Recommendations to prevent and control iron deficiency in the United States. MMWR Recomm Rep. 1998;47:1-29.