The risk of miscarriage may be higher among women who take certain anti-inflammatory drugs in early pregnancy, a new study suggests.

The nonsteroidal anti-inflammatory drugs or NSAIDs in the study included ibuprofen such as Advil, naproxen, diclofenac, and celecoxib (Celebrex), some of the most common medications used during pregnancy, according to earlier research. 

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Ultrasound was used to confirm the pregnancies in the painkiller study. (Joshua Lott/Reuters)

To look at the risks, Anick Bérard of the University of Montreal and her colleagues analyzed data from drug and hospital databases in Quebec, including a registry of all pregnancies in the province since 1997.

"The use of nonAspirin NSAIDs during early pregnancy is associated with statistically significant (2.4-fold increase) of having a spontaneous abortion," the researchers concluded in Tuesday's issue of the Canadian Medical Association Journal.

"Given that the use of nonAspirin 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, nonAspirin NSAIDs should be used with caution during pregnancy."

Normally, the risk of clinically detected miscarriage is about 15 per cent. The doubling of risk associated with use of NSAIDs raises the risk up to 30 per cent, Bérard said.

More women who had miscarriage had other illnesses in the year before pregnancy than those who did not, the investigators said.

Those in the miscarriage group were also slightly older, and more tended to live in an urban area and receive social assistance.

The data in the study covered 36 per cent of pregnant women in the province, which the study's authors said could affect how the findings may be generalized to the wider population.

But a recent paper from Sweden found that when women were interviewed, many who were prescribed medications in pregnancy never took the drugs, said Dr. Gideon Koren, director of the Motherisk program at Toronto's Hospital for Sick Children.

Scares women

"The problem is that type of study does not prove anything, but they scare the hell out of women and health professionals," said Koren.

There are pregnant women with conditions such as arthritis, lupus or chronic pain who need the medications, said Koren, noting the findings do not change Motherisk's advice.

The study's authors only looked at prescribed NSAIDs. The NSAID ibuprofen is also available over-the-counter in Quebec. Since all women were equally likely to buy the drug over-the-counter, Bérard said that the omission likely would have resulted in an underestimation of risk. 

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NSAIDs should be used with caution during pregnancy, Anick Berard says. (Canadian Press)

Another problem with studying miscarriage is that it can happen before a woman knows she is pregnant, which makes this type of research complicated, said Koren, who counsels women and health care professionals about using drugs in pregnancy.

For women using NSAIDS to relieve acute pain such as headache, alternative therapies like acetaminophen may be used during the first trimester, Bérard suggested.

The researchers looked at miscarriages or spontaneous abortions that occurred up to 20 weeks into pregnancy.

Christa Hassell of Toronto is due on Wednesday. Hassell said she heard of the advice to avoid NSAIDs in pregnancy.

"Mostly I would just try to deal with headache or cold or whatever without any medication," Hassell said.

The study was funded by Quebec's health ministry and the province's medication use research body.

With files from CBC's Kelly Crowe and Melanie Glanz