August 20, 2018 • Brent Bauer, M.D., Mayo Clinic
Nourishing your body with a healthy diet is always important, but even more so when you're eating for two. Although your baby needs a steady stream of vitamins and minerals in the womb, your own nutrient needs increase significantly as your body performs the work of pregnancy.1 And making sure your body has the right amount of iron – a mineral essential to red blood cell production – is a must.
Without an iron boost in your diet, you could be at risk of anemia, which is the condition of not having enough healthy red blood cells to carry oxygen to your body's tissues.
Anemia makes you feel tired and weak at any stage of your life, but during pregnancy it can have many effects – and some of them might surprise you.
A low iron level, also called iron deficiency, is the cause of most cases of anemia during pregnancy.2,3
How iron delivers oxygen to you and your baby
Iron has an essential role in the formation of new red blood cells, which contain hemoglobin, the iron-rich protein that gives blood its red color. Hemoglobin enables red blood cells to carry oxygen from the lungs to the tissues throughout your body – and, when you're pregnant, to your developing baby. To keep up with your body’s oxygen demand during pregnancy, you need 15-30% more red blood cells than you had before you were pregnant.4
But to form these red blood cells the body's need for iron increases dramatically.4
Some women have enough iron reserves built up to meet their own needs, as well as their baby's, if they stick with a healthy diet. But many women don't. As your pregnancy progresses and your body uses up more stored iron, you could be at risk for low iron. In fact, 1 in 5 women in the U.S. develops an iron deficiency by the end of pregnancy – and worldwide, 40% of pregnant women have anemia.2
Personal factors can predict your iron supply
Just being pregnant increases your risk of iron deficiency. But your risk is especially high if your iron stores are already low or depleted for other reasons, such as:
Getting pregnant during adolescence
Getting pregnant soon after a previous pregnancy
Being pregnant with multiple fetuses
Vomiting because of morning sickness
Having a history of heavy periods
Having a history of anemia
Eating a diet that is low in iron (especially being vegetarian or vegan)
Having bariatric (weight loss) surgery, such as gastric bypass, gastric banding, or sleeve gastrectomy
Whether or not you have known risk factors for anemia, your health-care professional likely will order a blood test to screen for this condition at your first prenatal visit. The results of this test will show how well your body has processed and stored iron historically, and how carefully you may need to be watched for changes as your pregnancy progresses.
The dangers of deficient iron during pregnancy
Mild anemia isn't likely to cause any health issues for you or your baby. But more severe anemia can be dangerous for both of you. 1-3,5-7
Severe anemia will put your baby at risk of: 1-3,5-7
Being born too early (premature birth)
Being born at a low birth weight
Developing anemia in infancy
As for the mother, severe anemia will put you at risk of:
Making it more difficult to fight infections
Losing too much blood during delivery
Having restless legs syndrome during pregnancy8
Developing postpartum depression
Signs and symptoms of anemia
Based solely on how you feel, it can be hard to recognize mild anemia during pregnancy. Many signs and symptoms are sneaky, because they seem like normal pregnancy changes. But if mildly low iron becomes severely low, then anemia’s signs and symptoms are more obvious:1-3
Fatigue and weakness
Pale or yellowish skin
Rapid or irregular heartbeat
Chest pain
Feeling lightheaded or dizzy
Cold hands and feet
Headache
Shortness of breath
Trouble concentrating
Dietary choices that increase your iron intake
Getting enough iron before you are pregnant helps prevent anemia during pregnancy. That is one of the reasons why health-care professionals recommend taking a prenatal vitamin before a woman conceives – ideally, on a daily basis during her reproductive years.9,10
In addition, make sure your regular diet includes plenty of iron-rich foods. Animal protein, including lean meats, poultry, and fish, provide a type of dietary iron called heme – the type of iron your body absorbs and utilizes most easily.
Many plant-based foods are good sources of non-heme iron. Some of the best choices to meet your iron needs include:
Dried fruits, such as raisins and apricots
Dried beans
Peas
Dark green leafy vegetables
Eggs
Peanuts
Iron-fortified foods, such as certain cereals, breads, and pastas
To enhance your body's absorption of iron, drink orange or other citrus juices or eat foods rich in vitamin C at the same time you eat high-iron foods.1,7
When foods don't fulfill your iron needs
If blood tests early in your pregnancy are normal, then you might not need more iron than what's included in your diet and your daily prenatal vitamin. As a general rule, pregnant women need at least 27 milligrams (mg) of iron each day.2
If your blood tests show that you have low iron, then your health-care professional will likely recommend an iron supplement.
The amount of additional iron you need will depend on how much iron is in your prenatal vitamin, what your current iron level is, and what form of iron is prescribed. Some forms of iron are better absorbed than others.
Taking antacids or calcium supplements can interfere with iron absorption, so if you use these, then take them at a different time than your iron supplement.11 And space your daily dose of iron at least 1-2 hours apart from foods that can block iron absorption: cheese, yogurt, eggs, milk, spinach, tea or coffee, and whole-grain breads, cereals, and bran.12
If you have had gastric bypass or small bowel surgery or you are unable to tolerate taking iron orally, then you might need intravenous iron administration.1,6
Take caution: Too much iron can be risky
If prenatal blood tests show your iron level is normal, then you might think that an iron supplement could add an extra health benefit during pregnancy. After all, is there such a thing as doing too much to protect your health and the health of your baby? When it comes to iron, the answer is yes.
Some women with excess iron in their body experience gastrointestinal side effects, like nausea, diarrhea, and constipation.7
More worrisome, studies link excess iron during pregnancy with an increased risk for gestational diabetes.9,13 Talk with your health-care professional about the risks and benefits of iron supplementation for your individual situation.
Filling in any gaps
Pregnancy is a critical time for optimizing a woman's health and nutrition, important for both the mother and her baby. Overall nutritional and caloric needs are greatly increased by pregnancy and breastfeeding. Taking a prenatal supplement helps fill any key nutrient gaps for a woman who is pregnant or lactating - times when diet alone might not be enough. Learn more about the importance of a prenatal supplement.
References
Garner C. Nutrition in pregnancy. https://www.uptodate.com/contents/search. [Accessed March 28, 2018.]
Auerbach M, Landy H. Anemia and pregnancy. American Society of Hematology. http://www.hematology.org/Patients/Anemia/Pregnancy.aspx. [Accessed March 28, 2018.]
Anemia in pregnancy. https://www.uptodate.com/contents/search. [Accessed July 25, 2018.]
Anemia in pregnancy. Merck Manual Professional Version. https://www.merckmanuals.com/professional/gynecology-and-obstetrics/pregnancy-complicated-by-disease/anemia-in-pregnancy. [Accessed March 28, 2018.]
Iron deficiency anemia during pregnancy: Prevention tips. Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/anemia-during-pregnancy/art-20114455.[Accessed March 28, 2018.]
Percy L, Mansour D, Fraser I. Iron deficiency and iron deficiency anaemia in women. Best Pract Res Clin Obstet Gynaecol 2017;40:55-67.
Friedrisch J, Friedrisch B. Prophylactic iron supplementation in pregnancy: a controversial issue. Biochem Insights 2017;10:1.
Kryger M, Avidan A, Berry R. Women's Health: The Menstrual Cycle. Atlas of Clinical Sleep Medicine. 2nd ed. Philadelphia, Pa.: Saunders Elsevier; 2014.
Pregnancy and birth: Do all pregnant women need to take iron supplements? PubMed Health. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072758/. [Accessed March 28, 2018.]
Prenatal vitamins. Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/prenatal-vitamins/art-20046945. [Accessed March 28, 2018.]
Iron. NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/. [Accessed March 28, 2018.]
Iron supplements. Mayo Clinic. https://www.mayoclinic.org/drugs-supplements/iron-supplement-oral-route-parenteral-route/precautions/drg-20070148. [Accessed March 28, 2018.]
Rawal S, Hinkle S, Bao W, et al. A longitudinal study of iron status during pregnancy and the risk of gestational diabetes: findings from a prospective, multi-racial cohort. Diabetologia 2017;6:249-257.
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