Several studies have shown it harms male reproduction while in the womb.
Now a review of three separate experiments on rats and mice, which have similar systems, suggest the same applies to females.
Dr David Kristensen, of Copenhagen University Hospital, said the finding is of “real concern” – particularly in the UK and other Western countries where the age at childbirth is “continuously being delayed”.
Official guidelines say paracetamol should be taken only if necessary in pregnancy – and for the shortest possible time.
Dr Kristensen said: “Although this may not be a severe impairment to fertility, it is still of real concern since data from three different labs all independently found that paracetamol may disrupt female reproductive development in this way, which indicates further investigation is needed to establish how this affects human fertility.”
The study published in Endocrine Connections said all three studies reported altered development in the reproductive systems of female offspring from mothers given paracetamol during pregnancy, which may impair fertility in adulthood.
The over-the-counter drug is the most widely used painkiller and is commonly taken by pregnant women worldwide, mainly for headaches and lowering temperature. It is deemed the only painkiller that is safe for mums-to-be.
Dr Kristensen said recent studies have linked it with disruptions in the development of the male reproductive system. But this was the first analysis of its kind to investigate its effects on female offspring.
It is well known that exposure to some chemicals during pregnancy can cause developmental effects that may not manifest until much later in life.
In rodents and humans, females are born with a finite number of eggs for reproduction in the future.
In the reviewed studies, which included research by the University of Edinburgh published two years ago, rats or mice that were given paracetamol during pregnancy produced female offspring with fewer eggs.
It meant in adulthood, they had fewer eggs available for fertilisation, reducing their chances of successful reproduction, particularly as they get older. The doses were equivalent to those a pregnant woman may take for pain relief.
Although there are parallels with rodent reproductive development, the findings published in Endocrine Connections have yet to be firmly established in humans.
It has been suggested paracetamol, as well as some other painkillers, may affect the development of ‘germ cells’ that mature into eggs and sperm within the womb.
The drugs may act on hormones called prostaglandins which are known to regulate ovulation, the menstrual cycle, and the induction of labour.
But Dr Kristensen said establishing a link between paracetamol taken by mothers during pregnancy and fertility problems much later in the adult life of the child will be difficult.
Experiments on babies in the womb would be impossible, which is why previous research has always been on rodents. Dr Kristensen recommends an interdisciplinary approach to address this.
He said: “By combining epidemiological data from human studies with more experimental research on models, such as rodents, it may be possible to firmly establish this link and determine how it happens, so that pregnant women in pain can be successfully treated, without risk to their unborn children.”
Added Dr Kristensen: “As scientists, we are not in the position to make any medical recommendations and we would urge pregnant women in pain to consult with their general practitioner, midwife or pharmacist for professional advice.”
Previous research by the same University of Edinburgh team whose work Dr Kristensen also found the drug lowered testosterone levels in male mice developing in the womb.
About 65 percent of pregnant women have taken paracetamol at some point in pregnancy, studies suggest. There is evidence that people consider it to be harmless.
But the painkiller has also been linked with increasing the risk of autism and ADHD (attention deficit hyperactivity disorder).
A study by Spanish researchers found boys whose mothers took it while expecting were 30 percent more likely to show signs of being on the autistic spectrum. It was also associated with higher rates of ADHD in both sexes.
The NHS advises pregnant women paracetamol is “usually safe” to take. But it recommends them to see their midwife or GP first.
But Dr Kristensen said: “Paracetamol is used worldwide by to treat pain and fever during pregnancy. It is therefore of concern that prenatal exposure has been linked to subsequent reduced fertility in experimental studies.”
He said exposure to paracetamol may compromise the “reproductive lifespan of women”.
Added Dr Kristensen: “Such an effect, even if small from prenatal paracetamol exposure, is problematic in the Western world where the age at childbirth is continuously being delayed.
“To follow up on these initial experimental studies, epidemiological studies are needed.”
The original article was published in the Independent.
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