Pregnant women were warned today not to take iron supplements unless they are anaemic.
The advice comes after a study found that women who took iron supplements in pregnancy were more likely to suffer from high blood pressure and deliver smaller babies.
The Food Standards Agency (FSA) already advises that pregnant women get iron from their diet rather than supplements.
In the past, iron has been recommended in pregnancy to help promote growth of the placenta and baby.
Research published today in BJOG: An International Journal of Obstetrics and Gynaecology found that iron supplements also increase the risk of copper and zinc deficiency in women.
The Iranian study followed 727 women who did not have anaemia, of whom 370 were given a 150mg ferrous sulphate (iron preparation) tablet every day throughout pregnancy while 357 were given a dummy pill.
The women were examined during pregnancy and for six weeks after delivery.
Researchers, from Tarbiat Modarres University in Tehran, found that women taking the tablets were more likely to develop high blood pressure and more likely to have a baby that was small for its gestational age (SGA).
Professor Saedeh Ziaei, who led the study, said: ‘The SGA birth rate and the number of women with hypertension disorder were higher in the women who received iron supplementation in comparison to the control group.
‘Because routine iron supplementation is common and our trial suggests that administering it may have some disadvantages in non-anaemic women, the rationale needs to be examined.’
Diet and nutrition
Professor Philip Steer, BJOG editor-in-chief, said: ‘Anaemia in women is often associated with low birth weight and pre-term births but that does not mean that women should be popping iron pills, or any vitamin pills indiscriminately, to prevent poor pregnancy outcomes.
‘Women who are not suffering from anaemia should ensure they receive proper advice on diet and nutrition from their doctors and midwives.
‘This study shows that iron supplements may have a harmful effect on women who do not need them in the first place.’
According to the FSA, pregnant women should ensure they eat plenty of iron-rich foods to avoid becoming deficient.
Foods rich in vitamin C – such as fruit or vegetables or a glass of fruit juice – should be taken with an iron-rich meal to help the body absorb it.
Good sources of iron include red meat, pulses, bread, dried apricots, dark green vegetables and fortified breakfast cereals.
Women are told to avoid eating iron-rich liver while pregnant.
If a woman’s iron levels become too low, her doctor or midwife may recommend a supplement.
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