Women who take iron on a daily basis during pregnancy may reduce their risk of having a low birth weight baby, a new study indicates.

Iron deficiency is currently the most widespread type of nutritional deficiency in the world. It is the most common cause of anaemia during pregnancy, affecting around 32 million women annually.

Anaemia is a condition caused by a lack of red blood cells. It means that the body's tissues and organs cannot get enough oxygen. Symptoms can include tiredness, dizziness, a pale complexion and palpitations. The condition is common during pregnancy because the demand for iron increases as the foetus needs its own supply too.

Previous studies have suggested a link between pregnancy anaemia and a risk of giving birth prematurely. However a link to other birth outcomes, such as the weight of the baby at birth, have so far been inconsistent, so UK and US scientists decided to investigate this further.

They analysed the results of over 90 studies relating to iron use and anaemia during pregnancy. Almost two million women were included in these studies.

Not surprisingly, the researchers found that iron use during pregnancy increased haemoglobin levels, significantly reducing the risk of anaemia. Haemoglobin is an iron-containing protein found in the body's red blood cells. It is responsible for carrying oxygen.

They also found that the use of iron did not appear to reduce the risk of giving birth prematurely.

The analysis did reveal that women with anaemia during the first or second trimester of their pregnancy had a significantly increased risk of having a baby with a low birth weight. However, this risk fell if they took iron during the pregnancy.

In fact, for every 10mg increase in iron per day - up to 66mg per day - the risk of developing anaemia fell by 12%, the baby's birth weight increased by 15g and the risk of having a low birth weight baby fell by 3%.

The World Health Organisation currently recommends that pregnant women take 60mg of iron per day.

"Our findings suggest that use of iron in women during pregnancy may be used as a preventive strategy to improve maternal haematological status and birth weight," the scientists said.

They called for future research in this area to focus on ‘feasible strategies of iron delivery'.

Details of these findings are published in the British Medical Journal.

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