Mothers who are anaemic in the first 100 days of pregnancy have a much higher chance of having a child with congenital heart disease, according to new research funded by the British Heart Foundation and published in the journal BJOG . As a result, researchers will now investigate whether taking iron supplements before and during pregnancy could help to prevent some heart defects at birth.
For the first time in the UK population, researchers have identified a link between congenital heart disease (heart conditions that develop in the womb, before a baby is born) and maternal anaemia in early pregnancy. The researchers estimate that maternal anaemia may account for around one in 20 congenital heart disease cases in the UK.
The study looked at data from 16,500 mothers and found that, if the mother was anaemic in the first 100 days of pregnancy, the likelihood of having a child with congenital heart disease was 47 per cent higher than the usual risk of around 1 in 100. This was after adjusting for other factors that can raise the risk of congenital heart disease, such as the mother's age.
It's estimated that nearly a quarter of pregnant women in the UK - and over a third of pregnant women globally - have anaemia. Severe anaemia in the later stages of pregnancy is known to cause problems such as low birth weight and premature delivery. But until now, little was known about the effect of anaemia in the early stages of pregnancy, while the fetal heart is developing.
In low- and middle-income countries, where anaemia during pregnancy is much more common, the researchers estimate that it may account for even more cases of congenital heart disease than in the UK.
Associate Professor Duncan Sparrow , British Heart Foundation Senior Research Fellow at the University of Oxford's Department of Physiology, Anatomy and Genetics , who led the research, said: 'We already know that the risk of congenital heart disease can be raised by a variety of factors, but these results develop our understanding of anaemia specifically and take it from lab studies to the clinic. Knowing that early maternal anaemia is so damaging could be a gamechanger worldwide.
'Because iron deficiency is the root cause of many cases of anaemia, widespread iron supplementation for women - both when trying for a baby and when pregnant - could help prevent congenital heart disease in many newborns before it has developed.'
Congenital heart disease is the most common kind of birth defect, diagnosed in at least one in every 150 births, an average of 13 babies a day in the UK. It is a major cause of death in infants.
The researchers previously found a link between anaemia during pregnancy and congenital heart disease in mice. To investigate this link in humans, they used anonymized data from a GP record database to see if the two conditions could also be linked in humans.
More than 2,700 mothers who had a child with congenital heart disease were identified. The researchers then found nearly 14,000 mothers at the same GP practices whose children did not have congenital heart disease, but whose pregnancies started at similar times.
Blood test results from the first 100 days of each pregnancy were used to determine whether the mothers had anaemia at the time. In the group of mothers who had a child with congenital heart disease, 4.4 per cent had anaemia. This was compared to 2.8 per cent of the mothers who did not have a child with congenital heart disease.
The researchers now want to confirm that anaemia specifically caused by iron deficiency is linked to congenital heart disease, as they found in their research in mice. If this is shown to be the case, the hope would be that researchers could trial iron supplements as a potential way of reducing cases of congenital heart disease in the future.
Dr Sonya Babu-Narayan, Clinical Director at the British Heart Foundation , said: 'If low iron turns out to be one of the culprits, then replenishing iron levels during early pregnancy when the baby's heart is forming could have significant benefit for a baby's lifelong heart health.
'Whilst observational studies like this can show us links, they cannot tell us about cause. Larger studies are needed to confirm the finding and determine which type of congenital heart disease may be linked to low iron. It is also important to note that the usual risk of having a child with a congenital heart disease is around 1 per cent, so even with the increase that this study suggests, the individual risk for people with no family history of congenital heart disease is still relatively small.'
The full paper, ' Maternal Anaemia and Congenital Heart Disease in Offspring: A Case-Control Study Using Linked Electronic Health Records in the United Kingdom ', can be read in BJOG .
