Pregnant women cautioned on use of paracetamol after study finds it changed the brains of male mice

Pregnant women have been cautioned against the use of paracetamol after new research showed that male mice exposed to the drug in the womb were less likely to mate with females.

The study results have left scientists divided over the continued use of paracetamol which is one of the few medicines recommended for use in controlling pain and fever in pregnant women.

The research found that male mice babies had a smaller number of neurons in brain areas connected to sexual behaviour when their mothers were fed paracetamol while pregnant.

These male mice pups were also found to be less aggressive than those born to mothers who were not exposed to paracetamol.

The male mice exposed to paracetamol in utero also had changed urinary marking patterns when they became adults and reduced ejaculations when mating with females.

These findings add to the growing body of evidence suggesting the need to limit the widespread exposure and use of APAP (paracetamol) by pregnant women, the Danish researchers say.

Earlier studies carried out by the same researchers found that prenatal exposure to paracetamol could result in developmental changes in the reproductive organs in rodents and humans.

It could lead to female infertility among adult rodents and malformations in newborn males.

Dr Rachel Hill the head of the Behavioural Neuroscience laboratory at Monash Medical Center says the perceived safety of paracetamol use in pregnancy is based on findings about absence of birth defects and maternal and neonatal well being.

The medication’s long term effects on reproductive behaviour have never been assessed before, she said.

The prenatal brain is particularly vulnerable as during this period several critical regions of the brain are forming and connecting to other regions, she says.

Therefore, factors that would generally not impact an adult brain could have severe effects on the developing prenatal brain.

Dr Hill says the zika virus is a good example of how an external factor has no effect on the adult brain but devastating effects on the foetal brain.

The research would suggest that Australian pregnant women should take caution when taking regular pain relief medication and consider the long-term impact these medications may be having on their developing child, she said.

The research is published in the journal Reproduction.