Paracetamol 'linked to childhood wheezing'
A study of 9,000 pregnant mothers found that just one percent took paracetamol most days or daily.
But those who took it this often in late pregnancy were twice as likely to have children who suffered wheezing at the age of three-and-a-half.
The authors of the study, published in the journal Thorax, said animal research had suggested that very high levels of paracetamol can damage airway linings.
But whether this could occur in a baby's developing lung in the womb is unknown.
They state that if painkillers are required, expectant mothers should still take paracetamol rather than aspirin, but they should not use it every day.
The research was based on interviews with pregnant mothers who were taking part in the Avon Longitudinal Study of Parents and Children.
The study team, led by Dr Seif Shaheen of King's College in London, interviewed the women about their use of paracetamol and aspirin when they were 18-20 weeks pregnant and again at 32 weeks.
Six months after giving birth and then every year, the mothers were asked about symptoms of wheezing and eczema in their children.
The research found that taking paracetamol every day or most days between 20 and 32 weeks of pregnancy was linked with a doubling in the risk of wheezing in the children when they were three-and-a-half years' old, compared with those whose mothers never took the drug during pregnancy.
The link was stronger still among children whose symptoms appeared before they were six months' old.
There was no evidence that less frequent use or heavy use of paracetamol before 20 weeks of pregnancy increased the risk of wheeze for children.
Nor was there anything to suggest that frequent use of paracetamol during pregnancy was linked to subsequent eczema in the children.
The researchers found that heavy use of aspirin was associated with a higher risk of wheeze but only in children under six months' old.
Aspirin use in late pregnancy is already discouraged because of the risk that a blood vessel in the foetus could close prematurely.
The study authors suggest it would also be prudent for women to avoid frequent use of aspirin during early pregnancy.
Overall they conclude: "We recommend that paracetamol should remain the analgesic of choice in pregnancy if used infrequently."
They pointed out that the link between paracetamol use in late pregnancy and wheezing during childhood could only account for 1% of the cases of wheezing seen among young children in the general population.
Dr John Harvey, chairman of the communications committee of the British Thoracic Society, said: "This is one of the first studies to show a link between paracetamol use in late pregnancy and wheezing in early childhood.
"Further research is needed in this area - particularly into dosage and frequency of paracetamol use - and should be fast-tracked.
"Paracetamol however remains the safest analgesic for pregnant women and only a very small percentage of pregnant women in this study took paracetamol daily or on most days during late pregnancy.
"Nevertheless we would recommend caution to pregnant women taking paracetamol and advise them to consult their GP if they are worried."
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