Pregnant women and women planning to become pregnant have been warned that taking certain painkillers could increase the risk of miscarriage by as much as 80 per cent.
However, obstetricians here are urging women not to be alarmed by the findings, published in today's British Medical Journal. The study indicates a link between miscarriage and non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen.
The study was carried out in a survey of 1,055 pregnant women in California. The researchers at the Kaiser Permanente Medical Care Program in Oakland found "the use of NSAIDs during pregnancy increased the risk of miscarriage by 80 per cent".
"The risk of miscarriage was much higher when NSAIDs were taken around conception or were used for more than a week," the authors say.
The overall risk of miscarriage is about 10 to 15 per cent during the first 12 weeks of pregnancy. This drops to about two per cent after 12 weeks and 0.5 per cent after the 16th week.
The findings appear to back up a 2001 study, carried out in Denmark, which also found links between NSAIDs and miscarriage.
A specialist in foetal medicine here, however, was yesterday urging women not to be alarmed by the findings. Dr Stephen Carroll, consultant obstetrician gynaecologist at the National Maternity Hospital, said he would "be cautious of the findings".
"Many of the women in this study may have been at high risk of miscarriage anyway," he said.
The Royal College of Obstetricians and Gynaecologists in London advised women "not to be unduly alarmed". Dr Carroll said aspirin was often prescribed to pregnant women who were known to be at risk of miscarriage because of its blood-thinning properties. Studies of women who have suffered recurrent miscarriages have found placental thrombosis and "sticky" blood to be a factor in some cases.
Dr Carroll agreed with the study that woman should be cautious about taking pain-killers in the first 12 weeks of pregnancy.
"The majority of us \ who use aspirin would normally prescribe it only after 12 weeks." He said there were weaknesses with the study, however. "One of the problems with the study is that many of the women in it were at high risk anyway. The authors say they controlled for that but they don't produce any hard data on this, so this weakens the findings."
He also said the fact that the study had not actually set out to study the links between NSAIDs and miscarriage "weakened" the findings. The primary interest of this study was prenatal exposure to magnetic fields. The authors say the findings "need confirmation in studies designed specifically to examine the apparent association".
Paracetamol remains safe to take during pregnancy.
