Women who take non-steroidal anti-inflammatory drugs (NSAIDs) during early pregnancy more than double their risk of miscarriage, finds research in the Canadian Medical Association Journal.
The increased risk was irrespective of type or dose of drug, finds the research, which excluded aspirin.
NSAIDs are among the most commonly used drugs during pregnancy, and concerns have been voiced about their potential impact before.
Canadian and French researchers assessed a total of 4705 cases of miscarriage up to the 20th week of pregnancy; 352 (7.5%) of the women had taken NSAIDs which did not contain aspirin. This group were compared with 47 050 women who did not miscarry, 1213 (2.6%) of whom had taken this type of NSAIDs.
The data came from the Quebec Pregnancy Registry, which provides information on filled prescriptions, physician visits and diagnoses, and hospital admissions during pregnancy.
The women ranged in age from 15 to 45 years on the first day of their pregnancy and were insured for their medications for at least one year prior to and during pregnancy.
Exposure was defined as having filled at least one prescription for any type of non-aspirin NSAID during the first 20 weeks of pregnancy or in the two weeks before the start of the pregnancy. Naproxen was the most commonly used non-aspirin NSAID, followed by ibuprofen.
The risk of miscarriage was 2.4 higher among those women who had taken NSAIDs that did not contain aspirin in early pregnancy than among those who had not taken these drugs.
The highest risk was associated with diclofenac alone and the lowest risk was in users of rofecoxib alone. But dose did not seem to affect overall risk.
"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," writes lead author Dr Anick Bérard, from the University of Montreal and the Director of the Research Unit on Medications and Pregnancy at CHU Ste-Justine.
Previous research has shown that non aspirin NSAIDs during early pregnancy are associated with a heightened risk of major congenital malformations, prompting the authors to conclude: “non aspirin NSAIDs should be used with caution during pregnancy."
But Dr Virginia Beckett, spokesperson for the Royal College of Obstetricians and Gynaecologists said that although the study added to the evidence on miscarriage, it did not assess the influence of other factors which may increase a woman’s chance of having a miscarriage, such as smoking and weight gain.
“It is safe to take paracetamol during pregnancy,” she said, adding: “if a woman takes an NSAID the risk of miscarriage is still very low.”