Epigenetics is spreading its wings out to the painkiller world, at least in an animal model. Of course, it is well-known that just about everything has been linked to causing cancer in rats. The International Agency for Research on Cancer (IARC) has studied hundreds and hundreds of compounds and only one substance has been placed into group 4 (probably not carcinogenic) so if your name gets mentioned in a meeting, you are going to be found to cause cancer.

So don't worry just yet. Unless you are raising money for an environmental group or work at a law group, there is a huge gas between rats and humans. 

They tested the effects of two painkillers in pregnant rats - paracetamol and a prescription-only painkiller called indomethacin, which belongs to the same class of drugs as ibuprofen and aspirin. The animals were given the drugs over the course of several days - four days for indomethacin or nine days for paracetamol. The effects of the drugs were seen within one to four days of the start of treatment.  

Tests found that when a mother was given painkillers during pregnancy, her female offspring had fewer eggs, smaller ovaries and smaller litters of babies than those not exposed to the drugs. Exposed male offspring were also found to be affected at birth - showing smaller numbers of cells that give rise to sperm in later life. However, their reproductive function recovered to normal levels by the time they reached adulthood.

In addition to affecting a mother's immediate offspring, the study showed that painkillers taken in pregnancy also affected the subsequent generation of rats. The team found that the resulting females - the granddaughters of the mother given painkillers in pregnancy - also had reduced ovary size and altered reproductive function.

There are similarities in the reproductive systems of rats and humans but  the pace of fetal development in humans is slower than it is in rats, so for that and numerous other reasons it would be crazy to extrapolate these results to pregnant women, so the team recommends that pregnant women should stick with current guidelines - use painkillers if you need them, but as always at the lowest possible dose and for the shortest possible time.

That goes if you are not pregnant, or not a woman also.