"It's thought of as one of the safest painkillers to take during pregnancy, but a new study has warned of the dangers of taking paracetamol when pregnant," the Daily Mirror reports.
This new research used data from a long-running UK-based study that recruited pregnant women in 1991 and 1992 and has followed their children ever since.
When the women were 32 weeks pregnant, they were asked how often they took paracetamol in the previous 3 months.
Researchers then looked at how this could be linked with behaviour issues in the women's children. They looked at a very wide range (135 in total) of measures used to identify behaviour and thinking problems.
They found that paracetamol use during pregnancy was linked to an increased "score" for 12 of these measures, mostly around hyperactivity or attention.
But the study does not prove paracetamol use in pregnancy causes behavioural problems in children. Although the authors considered various health, lifestyle and environmental factors, others could be having an influence on the links.
The study assessed a wide range of behavioural measures, which unavoidably increases the possibility of finding some links by chance. It's also not possible to link this with any dose or frequency of paracetamol.
If you're pregnant and feel you need to take painkillers, paracetamol is usually safe to take. But if you find you're needing to take paracetamol regularly, speak to your doctor or midwife.
Find out more about taking paracetamol in pregnancy.
Where did the story come from?
The study was carried out by researchers from the University of Bristol and was funded by the UK Medical Research Council and the Wellcome Trust.
The UK media took the findings of the study at face value without recognising the limitations. It is not helpful to report that "Women who take paracetamol while pregnant risk having children with behaviour problems". An established risk has not been confirmed by this study.
What kind of research was this?
The cohort, also known as the "Children of the 90s", has followed around 14,000 parents and their children in the Bristol area collecting health and lifestyle information.
Cohorts can look at links between potential exposures and later health outcomes, but they cannot prove that one has caused the other. Many things may have influenced whether or not the mother took paracetamol in pregnancy, and whether the child had behaviour problems.
What did the research involve?
The ALSPAC cohort included 14,150 pregnant women who completed questionnaires at around 32 weeks of pregnancy. This included a question asking how often they had taken paracetamol within the last 3 months. Response options were every day, most days, sometimes or not at all.
The children involved in ALSPAC have been given various cognition (thinking) and behaviour tests, including:
- temperament tests at 6, 24 and 38 months
- behavioural tests at 2 years, and then at 6, 9 and 11 years
- tests of anxiety, compulsions, activity and attention problems at 7 years
- feeding patterns at 7 years
- IQ tests at 8 and 15 years
- memory tests at 8, 10 and 17 years
In this study researchers wanted to test the theory that taking paracetamol between 18 and 32 weeks of pregnancy increases the risk of behavioural problems, particularly hyperactivity and conduct disorders. They then looked at any links with cognitive tests.
In total the researchers looked at 135 cognitive or behavioural measurements and their relationship with paracetamol.
The analyses took account of potential confounding factors that may be linked with use of paracetamol during pregnancy:
- the mother's medical history (including migraine and back pain)
- the mother's general pregnancy health (such as whether she had a cold or flu, or mothers reported 'poor health')
- lifestyle factors such as diet and alcohol use
- number of previous children
- individual social factors, such as living in low-income housing
What were the basic results?
Only 0.9% of mothers reported taking paracetamol on most days and 0.2% every day. The vast majority reported taking it only sometimes.
After adjusting for confounders, the researchers found that 12 out of 135 cognitive or behavioural measurements were significantly linked with paracetamol intake in pregnancy.
These 12 measures were all related to hyperactivity or attention and included:
- being less adaptable at 6 months
- having poorer persistence scores at 24 months; this is a measurement of how willing a child is to persist in a task or activity they initially find difficult or frustrating
- having higher scores on the maternally-reported hyperactive behaviour scales at 42 and 47 months
- conduct problems at 42 to 47 months
- having poorer scores on teacher-reported attention at age 7 to 8 years
There were few cognitive or behavioural links seen after 7 to 8 years.
How did the researchers interpret the results?
The researchers conclude: "If paracetamol use in mid‐to‐late pregnancy has an adverse effect on child neurocognitive outcome, it appears to mainly relate to the pre‐school period. It is important that these results be tested using other datasets or methodologies before assuming that they are causal."
The Avon cohort is a valuable data source that has allowed researchers to assess various links between parent and child health.
However, as the researchers of this latest study rightly caution, this study cannot prove cause and effect.
Various health, lifestyle and environmental factors may influence the likelihood of the mother taking paracetamol during pregnancy, and of the child having behavioural or attention problems.
The researchers have made careful attempts to identify and adjust for various maternal factors that were related but there may be other factors that were not taken into account.
Other limitations include:
- The study assessed links between paracetamol and 135 different cognitive and behavioural outcomes. The more variables that are looked at, the more likely it is to find links by chance
- Only 1% of this cohort took paracetamol on most days or every day. The vast majority took it "sometimes". If there is a true link between paracetamol use and child behavioural problems, it's not possible to link this with any frequency or dose of paracetamol
- The study found links with 12 hyperactive or attention test scores at various ages, but there's no way of knowing whether the score differences would make a difference to an individual child's everyday home or school life
- These measures were all taken from children around 20 to 30 years ago in the 90s. Though you might expect the findings to be just as representative of pregnant women and their children today, we cannot be sure this is the case
There is currently no clear evidence that paracetamol will harm your baby, and it is understood to be safe to take during pregnancy or while breastfeeding. But as with any medicine, taken during pregnancy, use paracetamol at the lowest effective dose for the shortest possible time. Find out more about taking paracetamol in pregnancy.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Daily Mirror, 16 September 2019
Mail Online, 16 September 2019
The Times (subscription required), 16 September 2019
Links to the science
Paediatric and Perinatal Epidemiology. Published online 15 September 2019