Paracetamol in pregnancy may harm baby


The over-the-counter pain-killer paracetamol is commonly used in pregnancy and considered safe by doctors, but results of a new study into its potential effects on the unborn baby are concerning.

Conducted by scientists at the Department of Pharmacy, University of Oslo, the study concluded that babies exposed in the womb to long-term paracetamol use by their mothers showed developmental problems as young children.

The study collected data from 48 631 Norwegian three-year-olds whose mothers reported taking paracetamol during pregnancy.

In the children who had been exposed to long-term paracetamol use (longer than 28 days) in utero, the researchers found significant evidence of developmental deficiencies.

The specific developmental problems observed were: poorer than normal gross motor development (gross motor skills are those used to move the whole body and the limbs, and include walking and balance); externalising behaviour (behaviour that involves aggression towards others); internalising behaviour (behaviour that involves harm to the self, such as occurs in depression, or being bullied); and higher than normal activity levels.

Even when the paracetamol use in pregnancy was short-term (1-27 days), the researchers observed poorer gross motor skills in children of these mothers; however the effects were smaller than with long-term use.

Recommended use in pregnancy

At this stage, there have not been any changes to recommendations regarding the use of paracetamol in pregnancy, says Information Pharmacist Briony Chisholm of the Medicines Information Centre, University of Cape Town.

She adds: "Certainly our advice to all pregnant women is to use as little medication as possible, for as short a duration as possible, once a risk/benefit assessment has been made with her clinician."

Other paracetamol concerns

Paracetamol is also known as acetaminophen, and is found in many brands of painkillers worldwide, such as Panado in South Africa and Tylenol in the United States, as well as products to relieve cold and flu. It is also used in combination with other drugs in prescription painkillers.

It is considered an effective mild painkiller, and safe when taken at recommended doses (for adults, 1000 mg single dose; maximum 4000 mg per day).

However, paracetamol overdose is among the commonest causes of drug overdose and is potentially fatal; it is a leading cause of acute liver failure.

Most drugs, both prescription and non-prescription, carry a risk of overdose. In the case of paracetamol, incidence of overdose is particularly high not only because the drug is so popular and ubiquitous but because the margin between the maximum safe dose (4000g) and one at which liver damage is likely (around 7500g, or even less) is small. The risk is even higher when paracetamol is combined with alcohol. 

A note on toxicity in animals

Paracetamol is also toxic to several animals. it is deadly for cats, who cannot metabolise it at all, and it should only be given to dogs, if at all, under strict veterinary supervision (as should any painkillers or other medication).

It is also highly toxic to snakes, and has been used as a  chemical control programme for the invasive brown tree snake in Guam: helicopters drop bait in the form of dead mice laced with Tylenol.

Allen AL (2003). "The diagnosis of acetaminophen toxicosis in a cat".
The Canadian Veterinary Journal.Brandlistuen, R. et al. (2013) Prenatal paracetamol exposure and child neurodevelopment: a sibling-controlled cohort study. International Journal of Epidemiology
Ferner, R. et al. (2011) "Management of paracetamol poisoning". British Medical Journal. BMJ 2011;342:d2218

Johnston J et al (2002). "Risk assessment of an acetaminophen baiting program for chemical control of brown tree snakes on Guam: evaluation of baits, snake residues, and potential primary and secondary hazards". Environmental Science and Technology.
Brandlistuen, R et al. (2013) "Prenatal paracetamol exposure and child neurodevelopment: a sibling-controlled cohort study". International Journal of Epidemiology.

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