Expecting mothers who take iron supplements may reduce their risks of delivering a low-birth weight baby according to a review of 92 studies. The researchers from Harvard University also found that these pregnant women were less vulnerable to iron-deficiency anaemia.

Low-birth weight babies are born weighing less than 2.5kg and because their tiny body is very fragile, they may be more predisposed to complications.

Study findings

Published in the British Medical Journal (BMJ), this research involved over two million pregnant women living in low, medium or high income countries.

After carefully analysing the studies, here’s what the scientists noted:

  • For every 10mg increase in daily iron intake, the mothers’ risk of anaemia dropped by 12% while their risk of giving birth to a small baby was reduced by 3%.
  • Women diagnosed with iron-deficiency anaemia within the first three or six months of gestation (the 1st or 2nd trimesters) were at greater risks of having a low-birth weight baby.
  • Taking iron supplements did not appear to influence the likelihood that the mother would deliver prematurely.
  • Compared to women who took low doses of iron, those who took larger amounts were less vulnerable to anaemia. These women were also less likely to give birth to a small baby. However, the researchers noted no extra benefit above 66mg of daily iron intake.

Do YOU need iron supplements?

Before you start popping pills; wait: You can have too much of a good thing when it comes to iron. Researchers found that non-anaemic women who took iron supplements could increase their risks of high blood pressure — a condition which would have adverse health consequences for both mother and baby.

In the UK, pregnant women are not routinely prescribed iron supplements unless their iron levels are low. So, if you are worried that you may be iron deficient or prone to iron deficiency, talk to your GP about the need for more sensitive tests like serum ferritin or total iron binding capacity (TIBC).

Planning to conceive? Do you have keep your iron status in check?

Catching and correcting iron deficiency before you try for a baby is the best way to avoid complications down the road. That’s because once baby is on her/his way, your blood volume will increase and so will your iron needs — correcting the deficiency then would be less easy.

What if you can’t cope with the supplements?

Unfortunately, many women ditch their iron pills because of digestive disorders like constipation, diarrhoea and nausea. If that’s your case, discuss with your GP about taking half the dose and gradually increasing to the full dose. If that’s not an option, ask whether you can cut your pill in two and take one half twice a day.

Pills do not substitute a healthy diet

Try to include an iron-rich food at every meal and avoid consuming tea or coffee 2 hours before and after your meal. If you’re a vegetarian or a vegan, boost your body’s iron absorption by taking a vitamin C rich food with your meal.


    Haider et al (2013) Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis. BMJ. 346:f3443.

    Ziaei et al (2007) A randomised placebo-controlled trial to determine the effect of iron supplementation on pregnancy outcome in pregnant women with haemoglobin > or = 13.2 g/dl. BJOG 114(6):684-8.