Painkillers such as ibuprofen double the risk of miscarriage in pregnant women, a study claims.
Scientists warn that tens of thousands of expectant mothers are taking the pills unaware of the dangers.
Women who took ibuprofen or similar painkillers just before they conceived until the 20th week of pregnancy were 2.4 times more at risk, Daily Mail reported Wednesday quoting the study.
Although there are clear warnings on the drugs' packets stating they should not be used in pregnancy, one in six expectant mothers still take them, the study claims.
The study involved a group of painkillers known as Non-Steroidal Anti Inflammatory Drugs or NSAIDs, which include over-the-counter ibuprofen and naproxen.
Aspirin is also in this category although it wasn't included in the study, while paracetamol is deemed safe.
Researchers believe taking any number of the drugs can lead to the embryo not being properly implanted in the womb, meaning a woman is far more likely to suffer miscarriage - also known as a spontaneous abortion.
Older women and those who smoke, drink heavily or are obese are at far higher risk.
The study published in the Canadian Medical Association Journal involved 47,050 women aged 15 to 45.
"We consistently saw that the risk of having a spontaneous abortion was associated with gestational use of diclofenac, naproxen, celecoxib, ibuprofen and rofecoxib alone or in combination," the Mail quoted researcher Anick Berard of the University of Montreal, as saying.