London: Taking painkillers such as ibuprofen during pregnancy may double a woman's risk of miscarriage, a new study has warned.

There are clear warnings on such drugs' packets that they should not be taken during pregnancy, but still one in every six expectant mothers take them unaware of the dangers, found the Canadian study.

Researchers at the University of Montreal who looked at a group of painkillers known as Non-Steroidal Anti Inflammatory Drugs or NSAIDS found that women who took them just before they conceived until the 20th week of pregnancy were 2.4 times more at the risk of miscarriage.

The NSAIDS drugs also included over-the-counter ibuprofen and naproxen. Aspirin is also in this category but it was not included in the study, while paracetamol is deemed safe, the Daily Telegraph reported.

For their study, published in the Canadian Medical Association Journal, the researchers surveyed more than 47,000 women aged 15 to 45 years.

They were asked whether they had taken the painkillers at any time in the first 20 weeks of their pregnancy -- or two weeks before they became pregnant.

Despite the warnings some 17 per cent, or nearly one in six, had taken the drugs, the researchers found.

Study author Dr Anick Berard said: "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.

"Women who were exposed to any type and dosage of non-aspirin NSAID during early pregnancy were more likely to have a spontaneous abortion."

The 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.

Around one in eight pregnancies end in miscarriage and the majority happen in the first 12 weeks. Often there is no obvious cause but older women and those who smoke, drink heavily or are obese are at far higher risk.

However, many experts pointed out the risks of a woman suffering a miscarriage due to painkillers were very small.

They also said the study did not take into account other possible causes such as smoking and obesity.

Dr Virginia Beckett, spokesman for the Royal College of Obstetricians and Gynaecologists, said: "It is important that any woman before conception and during pregnancy plans their pregnancy and reduces their risk of any complications through maintaining a healthy lifestyle.

"It is safe to take paracetamol during pregnancy," Dr Beckett added.