Women who take any amount of ibuprofen in early pregnancy could more than double the risk of miscarriage, new research suggests.
A class of painkillers known as non-steroidal anti-inflammatory drugs (NSAIDs) increases the risk of miscarriage in the first 20 weeks of pregnancy, experts said. Previous studies have shown inconsistent results when examining the effect of NSAIDs on pregnancy.
The new study, published in the 'Canadian Medical Association Journal', examined a number of commonly-used NSAIDs including ibuprofen, naproxen and diclofenac.
The research found that women who took any type, and any dose, of NSAID had a 2.4 times higher risk of miscarriage than those who did not use any.
Overall, 4,705 cases of miscarriage were analysed, of which 352 (7.5pc) involved women taking NSAIDs.
Women in the entire sample were aged 15 to 45, and they were compared with women of a similar age who did not suffer a miscarriage (of which 2.6pc had been exposed to NSAIDs).
The highest risk was for diclofenac when used alone, while the lowest was for rofecoxib, which was withdrawn in 2004 over safety concerns.
Dr Anick Berard, from the University of Montreal, who worked on the study, said: "The use of non-aspirin NSAIDs during early pregnancy is associated with statistically significant risk (2.4-fold increase) of having a spontaneous abortion.
"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, suggesting a class effect."
The authors concluded: "Women who were exposed to any type and dosage of non-aspirin NSAID during early pregnancy were more likely to have a spontaneous abortion.
"Given that the use of non-aspirin NSAIDs during early pregnancy has been shown to increase the risk of major congenital malformations and that our results suggest a class effect on the risk of clinically detected spontaneous abortion, non-aspirin NSAIDs should be used with caution during pregnancy."
Janet Fyle, professional policy adviser at the Royal College of Midwives, said: "We need to advise women, as midwives often do, to avoid buying over- the-counter medication for pain relief.
"If a pregnant woman does need to take any analgesia, then paracetamol would be appropriate.
"This would be after assessment by the midwife/or GP as to the nature of the pain.
"The most important advice to pregnant women is to report any pain to the midwife and avoid buying over-the-counter medication, as it may be contraindicated in pregnancy."
Dr Virginia Beckett, spokesperson for the Royal College of Obstetricians and Gynaecologists, said: "This study adds to the research base surrounding miscarriage, however it does not look at other factors which may increase a woman's chance of having a miscarriage such as smoking and weight gain.
"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, however, if a woman takes an NSAID the risk of miscarriage is still very low."