Treatments for anaemia in pregnancy thought to be due to iron deficiency

When the blood has insufficient red cells, or the red cells carry insufficient haemoglobin to deliver adequate oxygen to the tissues, this is called anaemia. There is normally a reduction in the haemoglobin concentrations in the mother's blood during pregnancy, and this allows a better blood flow around the womb (uterus) and to the baby. This is sometime called physiological anaemia and needs no treatment. True anaemia, however, can be mild, moderate or severe and can cause weakness, tiredness and dizziness. Severe anaemia makes women at risk of cardiac failure and is very common in low-income countries Anaemia has many causes including a shortage or iron, folic acid or vitamin B12. These are all required for making red cells and are available in a good diet. Iron shortage, however, is the most common cause of anaemia during pregnancy. Iron treatment can be given by mouth (oral), by injection into the muscle (intramuscular) or injection into the vein (intravenous). Blood transfusion or giving something which stimulates the body to produce more red cells (erythropoietin) are also possible treatments.

In this review, we identified 23 trials involving 3198 pregnant women. Many of the trials were in low-income countries and many treatment variations were studied. Oral iron reduced the incidence of anaemia but is known to sometimes cause constipation and nausea. Although the intramuscular and intravenous routes produced better levels of red cells and iron stores than the oral route, no clinical outcomes (such as pre-eclampsia, preterm births, postpartum haemorrhage) were assessed and there were insufficient data on adverse effects. Intravenous treatment can cause venous thrombosis (blockages in the veins) and intramuscular treatment causes important pain and discolouration at the injection site. It was unclear if women and babies were healthier when women were given iron for mild or moderate anaemia during pregnancy. There were no studies on using blood transfusions.

Overall, there was insufficient evidence to say when or how anaemia in pregnancy needs to or should be treated.

Authors' conclusions: 

Despite the high incidence and burden of disease associated with this condition, there is a paucity of good quality trials assessing clinical maternal and neonatal effects of iron administration in women with anaemia. Daily oral iron treatment improves haematological indices but causes frequent gastrointestinal adverse effects. Parenteral (intramuscular and intravenous) iron enhances haematological response, compared with oral iron, but there are concerns about possible important adverse effects (for intravenous treatment venous thrombosis and allergic reactions and for intramuscular treatment important pain, discolouration and allergic reactions). Large, good quality trials, assessing clinical outcomes (including adverse effects) as well as the effects of treatment by severity of anaemia are required.

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Background: 

Iron deficiency, the most common cause of anaemia in pregnancy worldwide, can be mild, moderate or severe. Severe anaemia can have very serious consequences for mothers and babies, but there is controversy about whether treating mild or moderate anaemia provides more benefit than harm.

Objectives: 

To assess the effects of different treatments for anaemia in pregnancy attributed to iron deficiency (defined as haemoglobin less than 11 g/dL or other equivalent parameters) on maternal and neonatal morbidity and mortality.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (7 June 2011), CENTRAL (2011, Issue 5), PubMed (1966 to June 2011), the International Clinical Trials Registry Platform (ICTRP) (2 May 2011), Health Technology Assessment Program (HTA) (2 May 2011) and LATINREC (Colombia) (2 May 2011).

Selection criteria: 

Randomised controlled trials comparing treatments for anaemia in pregnancy attributed to iron deficiency.

Data collection and analysis: 

We identified 23 trials, involving 3.198 women. We assessed their risk of bias. Three further studies identified are awaiting classification.

Main results: 

Many of the trials were from low-income countries; they were generally small and frequently methodologically poor. They covered a very wide range of differing drugs, doses and routes of administration, making it difficult to pool data. Oral iron in pregnancy showed a reduction in the incidence of anaemia (risk ratio 0.38, 95% confidence interval 0.26 to 0.55, one trial, 125 women) and better haematological indices than placebo (two trials). It was not possible to assess the effects of treatment by severity of anaemia. A trend was found between dose and reported adverse effects. Most trials reported no clinically relevant outcomes nor adverse effects. Although the intramuscular and intravenous routes produced better haematological indices in women than the oral route, no clinical outcomes were assessed and there were insufficient data on adverse effects, for example, on venous thrombosis and severe allergic reactions. Daily low-dose iron supplements may be effective at treating anaemia in pregnancy with less gastrointestinal side effects compared with higher doses.

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