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Heavy Paracetamol Use In Pregnancy Linked To Childhood Wheezing

28 October 2002

Women who frequently use paracetamol in late pregnancy may increase the risk of wheezing in their offspring, new research suggests.

Women who frequently use paracetamol in late pregnancy may increase the risk of wheezing in their offspring, new research suggests.

Over 9,000 mothers and their children, who were taking part in the Avon Longitudinal Study of Parents and Children (ALSPAC), were studied by researchers from King’s College, London and Bristol University. This study, popularly known as the Children of the 90s, has monitored the health and development of more than 14,000 families since 1991. The mothers gave the information by completing questionnaires.

The researchers found that children whose mothers had taken paracetamol on most days or every day during the second half of pregnancy were twice as likely to wheeze through early childhood as children whose mothers never took paracetamol.

Neither less frequent use, nor use in early pregnancy, was associated with wheezing, nor was any relation seen between paracetamol use in pregnancy and eczema in the children.

The researchers suggest that heavy exposure of the fetus to paracetamol may damage the airways of the developing lung, leading to wheezing after birth. However, lead author Dr. Seif Shaheen of King’s College, London, whose work on paracetamol use was funded by the Department of Health, cautions that it is not possible from these data to say conclusively that heavy paracetamol use in pregnancy causes wheezing in the offspring.

Dr Shaheen adds that they are not able to say at this stage whether heavy paracetamol use in pregnancy might be associated with asthma in the children when they are older.

“Even if the link with wheezing is causal,” says Dr Shaheen, “only about 1% of all wheezing in children in the ALSPAC population could be explained by paracetamol use, because very few of the mothers took paracetamol on most days or every day.”

Dr Shaheen went on to emphasise that paracetamol should remain the painkiller of choice for pregnant women, as long as they do not take it for more than a few days each week. He says, “These findings add to growing evidence that a baby or child’s risk of wheezing is partly determined by their environment in the womb.”

  • Dr. Seif Shaheen will be speaking on his findings at a press briefing, organized to coincide with the special presentation day taking place on Monday 28th October at the Royal Society for the world-renowned Children of the 90s study. The briefing will be at 10am at 6-9 Carlton House Terrace, London SW1.
  • The presentation day brings together the researchers working on the ALSPAC study with many of the top names in the scientific world, to showcase the latest findings and ongoing work of this vast epidemiological undertaking, much of which is funded by the Wellcome Trust and the Medical Research Council.
  • On the agenda will be news of a further £1.2 million funding from the Wellcome Trust that will allow the project to look into the reasons why obesity is so prevalent in today’s children.
  • Health Minister, Lord Philip Hunt, whose department gave grants for Dr Shaheen’s work on paracetamol use, said of the study: “These fascinating findings show that long-term studies like Children of the 90s and the forthcoming UK Biobank, yield valuable results that have a beneficial impact on the health of the nation.
    Taken together, these studies will inform us how genes, environment and lifestyle interact in health and disease, and will ultimately lead to new preventative measures to avoid illness, and lead to tailored medications.”

Shaheen SO, Newson RB, Sherriff A, Henderson AJ, Heron JE, Burney PGJ, Golding J for the ALSPAC Study Team. "Paracetamol use in pregnancy and wheezing in early childhood." Thorax 57; 958-963 doi:10.1136/thorax.57.11.958


1. Please acknowledge Children of the 90s in any reporting.

2. The Wellcome Trust is an independent research funding charity, established under the will of Sir Henry Wellcome in 1936. It is funded from a private endowment which is managed with long-term stability and growth in mind. The Trust's mission is to foster and promote research with the aim of improving human and animal health.

3. The Wellcome Trust and the Medical Research Council are major funders of the Children of the 90s study, and together with the Department of Health they also fund the UK Biobank study. More information on the UK Biobank is available at:

4. The Medical Research Council (MRC) is a national organisation funded by the UK tax-payer. Its business is medical research aimed at improving human health; everyone stands to benefit from the outputs. The research it supports and the scientists it trains meet the needs of the health services, the pharmaceutical and other health-related industries and the academic world. MRC has funded work which has led to some of the most significant discoveries and achievements in medicine in the UK. About half of the MRC’s expenditure of over £412 million is invested in its 50 Institutes, Units and Centres, where it employs its own research staff. The remaining half goes in the form of grant support and training awards to individuals and teams in universities and medical schools. Web site at:

Dr Shaheen Has Prepared Some Answers For Use By The Media In Anticipation Of Frequently Asked Questions:

Paracetamol use in pregnancy and wheezing in early childhood: questions and answers

Were we looking for a possible link?

Yes. We have previously found evidence for a possible link between frequent paracetamol use and asthma.

What were the key findings?

We have found that frequent paracetamol use (most days/daily) in late pregnancy (>20 weeks), but not in early pregnancy, was associated with an increased risk of wheezing in the offspring in infancy and early childhood (up to three and a half years old).

Less frequent use of paracetamol in late pregnancy was not associated with an increase in wheezing in the child.

There was no relation between paracetamol use in pregnancy and eczema in the child.

Frequent use of aspirin in pregnancy was associated with an increased risk of wheezing in infancy (<6 months) only.

What is our interpretation of the findings?

1) Frequent use of paracetamol in late pregnancy may cause wheezing in the offspring, but we cannot be certain that the link is causal in this sort of study – it might be explained by some other factor that we have not taken account of which is associated with paracetamol use by the mother and also with wheezing in the child.

2) If it is a causal link, then we speculate that heavy exposure of the fetal lung to the metabolites of paracetamol (and to aspirin) may cause wheezing after birth by interfering with normal development of the airways, but this is speculative and the exact mechanisms are not known.

Could paracetamol use in pregnancy be an important cause of wheezing in children?

No. We only found a link with frequent use and very few women took paracetamol this often (only 1%). Hence, even if the link is causal, we estimate that paracetamol use in pregnancy could only account for about 1% of wheezing in early childhood in the population.

Can we say whether frequent paracetamol use in pregnancy is linked to asthma and is further research being done?

At present we do not know, but we are investigating the possibility in the same cohort of children who are now of school age.

Should pregnant women stop using paracetamol in pregnancy?

In general medication should be avoided as much as possible in pregnancy. However where a product is considered necessary, Paracetamol should remain the preferred analgesic. However, it would be prudent for pregnant women not to take it too frequently in late pregnancy if possible. We would recommend that they do not take it for more than 1-2 days per week, and do not exceed recommended doses.

Should mothers stop giving paracetamol to infants and young children?

No. We were not able to reliably investigate whether frequent use in infancy was associated with subsequent wheeze or eczema. Paracetamol should be regarded as safe in young children in recommended doses and under no circumstances should they be given aspirin instead, because of a rare but potentially fatal complication called Reye’s syndrome. However, it must be remembered that paracetamol is a powerful drug and should be used in moderation.

Other advice to mothers:

Avoid frequent aspirin use throughout pregnancy (aspirin is usually discouraged in late pregnancy anyway).

Do not switch from paracetamol to aspirin or non-steroidal antiinflammatory drugs such as Ibuprofen if you have asthma, because of potential sensitivity reactions with these analgesics.



ALSPAC The Avon Longitudinal Study of Parents and Children (also known as Children of the 90s) is a unique ongoing research project based in the University of Bristol. It enrolled 14,000 mothers during pregnancy in 1991-2 and has followed most of the children and parents in minute detail ever since.


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