Women who take common painkillers or aspirin during pregnancy increase their risk of miscarriage by 80 percent, according to a study published in this week's British Medical Journal.

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Researchers in California interviewed 1,055 pregnant women immediately after their pregnancy was confirmed about their drug use since they became pregnant and their reproductive history.

They found that women who used nonsteroidal anti-inflammatory drugs -- such as ibuprofen and other painkillers -- during pregnancy had an 80 percent increased the risk of miscarriage. The risk was much higher when NSAIDs were taken around conception or were used for longer than a week.

Aspirin was also linked to an increased risk of miscarriage, but acetaminophen was not, regardless of timing and duration of use.

All three drugs work by suppressing the production of certain fatty acids that are needed for an embryo to implant in the womb. Because NSAIDs and aspirin act on the whole body, they could lead to abnormal implantation that leads to miscarriage, according to the study.

But acetaminophen acts only in the central nervous system, which may explain why it has no effect on risk of miscarriage, the researchers said.

They said that although the findings will need confirmation, women who are planning to be pregnant may consider avoiding the use of NSAIDs around conception.