Iron deficiency anaemia in pregnancy

This is a condition caused by a lack of red blood cells or haemoglobin. In the UK, the most common reason for developing anaemia is not having enough iron. 

Haemoglobin is a protein found in red blood cells. It picks up oxygen from your lungs and carries it around the body. A key ingredient used to make haemoglobin is iron. If there isn’t enough iron stored in your body, then the amount of haemoglobin drops. When haemoglobin reaches a low level, less oxygen can be carried in your blood. This can cause symptoms such as:

• Tiredness
• Breathlessness
• Heart palpitations (fast heartbeat)
• Weakness    
• Headache 
• Dizziness 
• Chest pain 
• Irritability 

There are several reasons why you might not have enough iron in your body: 

• There might not be enough iron in your diet. 
• Your gut may not absorb enough iron from your food (even if you have an iron-rich diet). 
• Your use of iron might be so high that you can’t get enough from your diet. Your baby needs a lot of extra iron when it’s growing in the womb. It gets the iron from you, which means that your own stores can become lower. 
• You may lose iron through bleeding, such as by having heavy periods before pregnancy, or because you have another medical condition. 

It is possible to have more than one of these causes, especially during pregnancy. Over 2 in 10 people in Europe are anaemic during pregnancy. A small proportion of cases of anaemia are due to other reasons, such as vitamin B12 or folate deficiency, or other medical conditions. We should be able to find out if it is due to this before giving you iron medication.

The main risk factors for developing anaemia in pregnancy are: 

• Already having low iron stores before becoming pregnant
• Having a pre-existing blood condition, such as sickle cell disease and thalassaemia
• Having an inflammatory bowel disorder which affects the gut’s ability to absorb iron from food. Examples of these include inflammatory bowel disease, coeliac disease, and previous surgery to the gut
• Having a higher demand for iron, such as having twins or triplets
• Being under 20 years old when you become pregnant
• Giving birth to your previous child less than 1 year ago
• Having anaemia in a previous pregnancy
• Having poor dietary habits
• If you follow a vegetarian or vegan diet

You may also be at risk of becoming anaemic after giving birth. This is often due to losing blood during or shortly after giving birth.

Anaemia can be detected by a simple blood test. As anaemia is so common in pregnancy, your community midwife will offer to check your haemoglobin levels. You will be screened for anaemia at your first booking visit, at 28 weeks and some people are also screened at 34 to 36 weeks of pregnancy.

If you are at increased risk of anaemia you may be screened more frequently.

If you are anaemic and or on treatment we would recommend repeating the blood tests after 2 to 3 weeks of having treatment, at 34 to 36 weeks of pregnancy and when in labour.

Anaemia during pregnancy is associated with many problems for you and your baby.  

Iron deficiency anaemia can affect your:

• muscle function
• ability to exercise (such as climbing the stairs) 
• bowel (gut) function

In pregnancy, iron deficiency also increases the risk of having: 

• a baby with a low birth weight 
• a premature birth

After giving birth, iron deficiency anaemia can:

• cause tiredness 
• reduce your milk production
• increase the risk of postnatal depression
• mean your our baby may have low iron stores at birth too
• increase the risk of you needing a blood transfusion during or after delivery. Giving birth often involves bleeding and sometimes this can be heavy bleeding. If you have iron deficiency anaemia it will increase your likelihood of needing a blood transfusion.

If you are less than 36 weeks pregnant, you will usually be offered a course of iron tablets. 2 to 4 weeks after you started taking iron medication you will be offered a repeat blood test to recheck your haemoglobin level. 

If the iron tablets work for you, your haemoglobin levels in your blood test should increase. If you had symptoms, you should start to feel better. This treatment will be explained in more detail in the iron tablets section. 

Sometimes iron tablets don’t work effectively enough, even when you take them every day and follow all the instructions. If this happens your GP will ask for some additional blood tests. These will include: 

• B12 and folate – these are important nutrients also used to make red blood cells. Low vitamin B12 or folate can also make you anaemic, even without iron deficiency. However, this is less common than iron deficiency anaemia.
• Ferritin – this is a protein in the blood which acts as an iron storage system. If your ferritin level is low, this means you don’t have enough iron. 

If you are more than 36 weeks pregnant, there may not be enough time for iron tablets to work before your baby is born. In this situation, you might need to be given iron directly into your bloodstream. This is called intravenous iron (IV iron) and is explained further in the IV iron section.

Diet 

A good balanced diet is needed to make sure you receive enough iron. 

The most easily absorbed iron comes from:

• red meat
• fish
• poultry – chicken, turkey etc.
• lentils
• fortified cereals
• leafy green vegetables such as spinach

Vitamin C can help your body to absorb iron from food. This is found in:

• orange juice
• fruits, especially orange, kiwi, strawberries, mango and tomatoes
• vegetables, especially broccoli, red cabbage, bell peppers, Brussel sprouts, cauliflower

Some foods can reduce your ability to absorb iron, so should be avoided around the time you eat iron rich foods and/or take your iron tablets. These include:

• tea
• coffee
• foods containing calcium such as milk and other dairy products and dairy alternatives, some seeds, pulses and vegetables, and many multivitamin tablets

For further information about iron-rich foods and foods to avoid please visit the NHS website and search for ‘iron’. 

Iron tablets 

Taking iron tablets are very effective at replacing the iron needed for haemoglobin levels to rise. Some iron tablets can also come with folic acid and vitamin C, which helps with the absorption of iron from the gut. The recommended tablets for treating iron deficiency anaemia are ferrous sulfate tablets. How well these iron tablets work is greatly affected by how they are taken. 

The best way to use them is to take a tablet with orange juice one hour before breakfast. If you don’t drink orange juice, then another drink containing vitamin C will also work. Your midwife or doctor will be able to advise you on alternative drinks. 

Your doctor or midwife will give you further guidance on how many iron tablets to take per day. You should take one tablet per day at most, and if it gives side effects then take one every other day. Taking more than one tablet per day is very unlikely to give you any extra benefit and may just make side effects worse. 

Side effects of iron tablets 

The most common side effects of taking iron tablets are some tummy pain, nausea, bloating, constipation and diarrhoea. If this stops you from being able to take the tablets, we can swap you onto a different type of iron tablet (ferrous fumarate) to see if the side effects reduce or to a lower dose at times.

After 2 to 4 weeks you will be offered another blood test to check if the iron tablets are working. If they are working, your haemoglobin level should rise. If your haemoglobin level is increasing steadily and at good speed you can simply keep taking the tablets. 

Once your haemoglobin is back to normal, you should keep taking the iron tablets for another 3 months. This helps to boost your body’s stores of iron, to prevent you from becoming anaemic again. 

If the iron tablets aren’t working, your GP will firstly check that you are taking them regularly and correctly. You may need more blood tests to rule out other causes of anaemia. 

Your doctor may refer you to hospital to have intravenous iron, if: 

• the tablets are not working
• you suffer from side effects which stop you from taking the tablets
• the tablets are not working quickly enough
• there is not enough time to make things better before your baby is due 

Information will be given to you if you are recommended to have an intravenous iron infusion.

Occasionally, treatments do not work and you will be offered a blood transfusion. Most pregnant women and birthing people with anaemia can be successfully treated with a change in diet and iron supplementation (with tablets or intravenously). However, if your haemoglobin levels become extremely low, or you are experiencing severe symptoms of anaemia, you may need a blood transfusion.  

Blood transfusions have some risks, particularly because the blood you receive is donated by another person. This is why we try to minimise the need for transfusion by supplementing iron with tablets or with IV infusion. 

However, blood transfusions are the only way to quickly correct severe anaemia. This could occur after a large bleed during delivery. If you need a blood transfusion, a doctor or midwife will explain this procedure further.

For more information, speak to your doctor (obstetrician, anaesthetist or GP) or midwife.

There are some useful online resourses:

• Iron deficiency anaemia on the NHS website
• Iron deficiency anaemia on Patient
• NHS Blood and Transplant (search anaemia)