Iron deficiency in pregnancy

A pregnant woman sitting down, taking tablets with a glass of water

The risk of developing anemia due to a lack of iron is greater in pregnant women. People who have anemia are advised to take iron supplements. In pregnant women who have normal iron levels, taking iron supplements as a precautionary measure probably doesn’t have any health benefits. They can get enough iron in their diet.

Iron is a mineral that is found in many proteins that the body needs in order to stay healthy. Most of the iron in our bodies is found inside hemoglobin (the pigment in red blood cells). Hemoglobin transports oxygen to all of the tissues and organs in our body. If there isn’t enough iron in the blood, the amount of hemoglobin in the blood decreases too. This can reduce the oxygen supply to cells and organs.

The body can store small amounts of iron. If you don’t get enough iron, your body will use these reserves to make hemoglobin. If your iron reserves are empty, you may already have symptoms like tiredness or headaches despite still having normal hemoglobin levels.

Anemia (a lack of healthy red blood cells) can develop over time. If it's caused by low iron levels, it's called iron-deficiency anemia. Because pregnant women need more iron, they are more likely to develop iron-deficiency anemia.

What are the consequences of iron deficiency in pregnancy?

Iron-deficiency anemia can make you feel tired or exhausted. Severe anemia can lead to complications in pregnancy. For instance, it can weaken the and increase the risk of infections. It also increases the risk of the baby weighing too little at birth (low birth weight). Mild anemia usually doesn’t affect the child, though.

Severe anemia is rare in healthy pregnant women who eat a balanced diet. In women who don't (or can’t) eat a balanced diet, though, anemia can become a serious health problem.

According to German health authorities, pregnant or breastfeeding women need 20 to 30 milligrams (mg) of iron per day. It can be particularly difficult for vegetarians to get that amount of iron in their diet alone.

How is anemia diagnosed?

Pregnant women regularly have blood tests as part of their standard check-ups. That way, iron-deficiency anemia can be detected early on and treated using iron supplements.

At the start and towards the end of pregnancy, hemoglobin levels above 11 grams per deciliter are considered to be normal. Between the fourth and sixth months of pregnancy, a small drop to 10.5 grams per deciliter is also considered to be normal. If the hemoglobin levels drop below that, the iron levels in the blood are measured too. This can help to determine whether the low hemoglobin levels are caused by a lack of iron.

Ferritin levels are also measured: That tells you how full your body’s iron reserves are.

Which foods have iron in them?

We normally get iron in the food we eat. Meat is especially rich in iron that can be absorbed well by the bowel. Liver is particularly high in iron.

It is harder for the body to absorb iron from plant-based foods. But some plants are good sources of iron too. These include cereals, for instance in the form of whole-grain breakfast cereals, and legumes such as lentils and beans. Green leafy vegetables like lamb’s lettuce and spinach contain some iron, too.

Illustration: Iron-rich foods

Iron can be taken as a dietary supplement as well. These are available without a prescription in the form of tablets and liquid drops.

When does it make sense to take iron supplements?

Iron supplements are usually already recommended for pregnant women whose iron reserves are going down, in order to prevent anemia. They are also a good idea if a more severe iron deficiency or iron-deficiency anemia is diagnosed. Then the doctor will usually prescribe a higher dose of iron supplements. You take them daily or every couple of days, depending on how severe the iron deficiency is. The supplements can reduce symptoms of the deficiency, such as tiredness.

Iron can also be given as an infusion (a drip). But that is only recommended if the body doesn't absorb enough iron through the bowel. Iron infusions are only an option from the fourth month of pregnancy.

Do women with normal iron levels benefit from taking iron supplements?

Pregnant women with normal blood iron levels sometimes take iron supplements to prevent anemia. But iron supplements are only a good idea if your doctor has diagnosed anemia or a significant iron deficiency. Too much iron can be harmful as well. When it comes to iron intake, finding the right balance is key. If you have a mild iron deficiency, getting more iron in your diet is often enough.

Side effects and dose

When taken in higher doses, iron supplements can cause gastro-intestinal symptoms such as constipation, nausea, vomiting and diarrhea. When taken on an empty stomach, they can damage the lining of the stomach. Infusions can cause short-term side effects such as a headache, back pain, itching or hot flashes.

Some experts recommend only taking iron supplements once or twice a week rather than every day – but at a higher dose (such as 120 mg). Research has found that iron supplements can even prevent anemia when taken only once a week. The idea is that taking iron supplements less often will enable women to take them for longer, and lower the likelihood of side effects. But it’s not clear whether that is really the case.

Keep iron supplements out of children’s reach

Like all other medications, iron tablets should be kept out of reach of children. Even if iron is “only” a natural mineral, an accidental overdose can be life-threatening for children. You should then call the emergency services (112 in Germany and many other countries, 911 in the U.S.), followed by a poison control center. People living in Germany can reach these centers here.

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Bundesinstitut für Risikobewertung (BfR). Höchstmengenvorschläge für Eisen in Lebensmitteln inklusive Nahrungsergänzungsmitteln. 2021.

Deutsche Gesellschaft für Hämatologie und Medizinische Onkologie (DGHO). Eisenmangel und Eisenmangelanämie (Leitlinie). 2022.

Gesellschaft für Pädiatrische Onkologie und Hämatologie (GPOH). Eisenmangelanämie (S1-Leitlinie). AWMF-Registernr.: 025-021. 2021.

Houston BL, Hurrie D, Graham J et al. Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials. BMJ Open 2018; 8(4): e019240.

Peña-Rosas JP, De-Regil LM, Garcia-Casal MN et al. Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev 2015; (7): CD004736.

Peña-Rosas JP, De-Regil LM, Gomez Malave H et al. Intermittent oral iron supplementation during pregnancy. Cochrane Database Syst Rev 2015; (10): CD009997.

Qassim A, Grivell RM, Henry A et al. Intravenous or oral iron for treating iron deficiency anaemia during pregnancy: systematic review and meta-analysis. Med J Aust 2019; 211(8): 367-373.

Rogozinska E, Daru J, Nicolaides M et al. Iron preparations for women of reproductive age with iron deficiency anaemia in pregnancy (FRIDA): a systematic review and network meta-analysis. Lancet Haematol 2021; 8(7): e503-e512.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on September 18, 2023

Next planned update: 2026

Publisher:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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