NEW YORK - Pregnant women considering a Caesarean section, with no clear medical reason for it, should know that the procedure is not without risk, Canadian doctors caution in a report published this week.

On the contrary, Dr. Shiliang Liu from the Public Health Agency of Canada, Ottawa, and colleagues have evidence that the rate of severe complications, such as major bleeding, infection and blood clots, is three-fold higher overall in women having a planned Caesarean section compared with women who planned a natural birth.

The researchers used a Canadian database to look at the outcomes of 46,766 women who underwent what doctors deemed to be a low-risk Caesarean delivery and nearly 2.3 million women who underwent planned vaginal delivery between April 1991 and March 2005.

Because the database didn't show if c-sections were performed solely because the mother requested it, the researchers explain, "we used Caesarean delivery for breech presentation as a surrogate for planned elective low-risk Caesarean delivery."

Liu's team found that the rate of severe complications in the planned Caesarean group was 27.3 cases per 1,000 deliveries, compared with 9.0 per 1,000 deliveries in the planned vaginal delivery group.

"Although the absolute difference is small," the risks should be considered by women thinking of asking for a Caesarean delivery, the investigators conclude in their article in the Canadian Medical Association Journal.

The study, writes Dr. B. Anthony Armson of the University of Toronto in a commentary, "provides additional support to a growing body of evidence suggesting that primary elective Caesarean birth may place both the mother and newborn at greater risk for adverse outcomes than planned vaginal birth."