Pregnant mothers who take paracetamol even at recommended doses might be harming the masculinity of their unborn son. And the common over the counter painkillers could reduce fertility in daughters too, a new study warned.
The study was published in the scientific journal Reproduction.Prof. David Mabjerg Kristensen, from the University of Copenhagen, said: “We have demonstrated that a reduced level of testosterone means that male characteristics do not develop as they should.”
While the new study focused on the effect of paracetamol on masculine characteristics, paracetamol during pregnancy also has the potential to influence the subsequent lives of female mice.
A study by the same researchers last year showed female mice had fewer eggs in their ovaries if their mothers had had paracetamol during pregnancy.This led to the mice becoming infertile more quickly.
But even if paracetamol is harmful, that does not mean it should never be taken, even when pregnant and women should consult their GP if concerned.Mabjerg Kristensen said: “I personally think that people should think carefully before taking medicine. These days it has become so common to take paracetamol that we forget it is a medicine. And all medicine has side effects.
“If you are ill, you should naturally take the medicine you need. After all, having a sick mother is more harmful for the foetus.”Mabjerg Kristensen noted previous studies found paracetamol can inhibit the development of the male sex hormone testosterone in male foetuses, increasing the risk of malformation of the testicles in infants.
But a reduced level of testosterone at the fetal stage is also significant for the behaviours of adult males.
The dosage administered to the mice was very close to the recommended dosage for pregnant women. And he said because the trials are restricted to mice, the results cannot be transferred directly to humans.
However, because of their certainty about the harmful effects of paracetamol meant it would be improper to undertake the same trials on humans.Testosterone is the primary male sex hormone that helps develop the male body and male programming of the brain.
The masculine behaviours in mice observed by the researchers involved aggressiveness to other male mice, ability to copulate and the need for territorial marking.The mice reacted significantly more passively than normal for all three parameters – they did not attack other males, were unable to copulate and behaved more like female mice when it come to urinary territorial marking.
After observing the changed behavioural patterns, Professor Anders Hay-Schmidt investigated the specific effects of a lack of testosterone on the brain.He said: “The area of the brain that controls sex drive – the sexual dimorphic nucleus – had half as many neurons in the mice that had received paracetamol as the control mice.“The inhibition of testosterone also led to a halving of the activity in an area of the brain that is significant for male characteristics.”