Anaemia in pregnancy: iron, B12 and folate

Anaemia occurs when there are too few red blood cells, or too little haemoglobin in them, to carry oxygen effectively. In pregnancy blood volume expands, which dilutes the red cells a little. A modest fall in haemoglobin is expected, so pregnancy has its own thresholds for what counts as anaemia, and your midwife or GP will explain your result.

Tommy's describes the condition as preventable and treatable. It matters because severe anaemia can leave you exhausted, more likely to need extra care at delivery and less able to cope with bleeding.

Tommy's lists tiredness, shortness of breath, palpitations and paler skin, which may look grey or yellowish-white on darker skin tones. The NHS adds headaches, ringing in the ears and unusual cravings for non-food items such as ice or soil, known as pica.

Many of these overlap with ordinary pregnancy tiredness, so the blood test result matters more than the symptoms. Tell your midwife if you are very breathless on mild effort, have a racing heart or feel faint.

Iron deficiency is the most frequent cause. Tommy's names inadequate dietary iron, difficulty absorbing it, heavy bleeding and the greater demands of pregnancy. Risk is higher with a vegetarian or vegan diet, previous anaemia, a multiple pregnancy, young maternal age, three or more previous pregnancies and a conception within a year of the last birth.

Vitamin B12 and folate deficiency cause a different form of anaemia with larger red cells. The NHS notes that in the UK the commonest cause is pernicious anaemia, and that complications can include problems in pregnancy and birth defects. Inherited conditions such as sickle cell disease and thalassaemia are further causes and are covered separately.

Tommy's says blood tests are done at the booking appointment and again at 28 weeks, a point at which the demand for iron is high and there is still time to correct it before birth. The test is a full blood count, and if it is low, ferritin and other measures may be added to find the cause.

B12 and folate are not routinely screened for, but Tommy's advises testing if there are symptoms such as extreme tiredness, a sore tongue, mouth ulcers, pins and needles, muscle weakness, vision problems or mood change.

The first-line treatment is iron by mouth, as tablets or liquid. The NHS says iron tablets generally need to be taken for around six months in iron deficiency anaemia outside pregnancy, and the pregnancy team will advise on duration. Side effects include constipation, stomach discomfort and dark stools, and taking tablets with food may help.

Tommy's says iron is best absorbed on an empty stomach with orange juice, and that tea and coffee reduce absorption. If tablets are not tolerated or do not work, intravenous iron or, rarely, a blood transfusion can be offered. For B12 and folate deficiency, the NHS describes B12 injections and folic acid tablets, with duration depending on the cause.

Food alone rarely corrects established anaemia, but it helps prevent it.

• Iron sources include red meat, fish, poultry, eggs, beans, leafy greens, dried fruit, nuts and fortified cereals.

• Vitamin C-rich foods or juice alongside meals improve absorption.

• Avoid tea and coffee with meals because they interfere with iron uptake.

• Vegans should take a B12 supplement, and folate comes from broccoli, asparagus, chickpeas and brown rice.

• Do not take cod liver oil or vitamin A supplements in pregnancy, as the NHS advises.

If haemoglobin is low close to term, the maternity team may recommend delivering in a consultant-led unit and plan for the possibility of heavier blood loss. Correcting iron before labour is a safer option than trying to treat anaemia during an emergency.

Supplements often continue after birth, and Tommy's confirms that prescribed iron is compatible with breastfeeding. A repeat blood count at the postnatal stage checks that levels are recovering.