OTTAWA (AFP) - Pregnant women are at a greater risk than the rest of the population of suffering serious complications from swine flu, Canadian health authorities warned.

"Thankfully, the majority of A(H1N1) illness in Canada is mild, but we are seeing that some people, including pregnant women, are more susceptible to serious illness and complications," said Health Minister Leona Aglukkaq.

Pregnant women who contract the flu virus strain run the risk of premature births and miscarriage, according to Chief Public Health Officer David Butler-Jones.

Research suggests that pregnant women are not more susceptible to the A(H1N1) virus, but are at a greater risk of complications if they do get infected, Butler-Jones told reporters.

He recommended that pregnant women take several precautions, ranging from following ordinary hygiene practices to "avoiding large crowds."

Three pregnant women were among a group of six people who have been admitted to intensive care after contracting swine flu in one Canadian province, said Danielle Grondin, an assistant deputy minister at the Public Health Agency of Canada. She declined to name the province.

Canadian health authorities said they had published guidelines for pregnant women infected with swine flu, as well as a factsheet with information for expectant mothers.

Canada has a reserve of antiviral vaccinations, including 55 million doses of Tamiflu and Relenza, which authorities said were effective treatments and safe for use by pregnant women.

A study is also underway to examine why some patients have developed more severe versions of the A(H1N1) virus than others.

More than 9,700 people in Canada have contracted the A(H1N1) virus, the Public Health Agency said.

So far, 894 cases have been severe enough to merit hospitalization, and 39 people have died from swine flu, it added.