Limiting the number of embryos used to get pregnant with in vitro fertilization (IVF) could reduce the number of newborn deaths, prevent cases of severe eye and brain damage, and cut the time babies spend in hospital, a Canadian study said.

In the case of Canada, this would prevent up to 40 newborn deaths in the country every year, and cut the time babies spend in intensive care units by 42,000 days annually, researchers led by Keith Barrington, at the University of Montreal, said.

The results reflect the potential reduction in the number of premature twins and triplets, who are at greater risk of health complications, than would occur under a policy of using just one embryo for each attempt to get pregnant with IVF, they said in the Journal of Pediatrics.

"If you by chance have a premature baby and are unlucky enough to have that child suffer with complications, that's one thing," Barrington told Reuters Health.

"But to actually have a procedure that increases the chance of that happening is something that should be changed."

During IVF, eggs are fertilized by sperm outside the body and then transferred to the womb. Transferring more than one embryo is thought to increase a woman's odds of getting pregnant, but it also increases her chance of multiple births.

Both Canada and the United States currently allow multiple embryos to be transferred in each IVF cycle.

In 2005, 29 per cent of IVF pregnancies in Canada were twins and about one per cent were triplets, the report said, which leads to a greater risk of premature birth.

Without fertility treatments, the rate of twins is about one per cent, while triplets occur in just one of every 8,100 births, according to the advocacy organization Multiple Births Canada.

The study said that if IVF were limited to one embryo for each attempt to become pregnant, there would be just three pairs of twins for every 100 deliveries, and no triplets. This drop in multiple births would greatly reduce the rate of premature births and the complications that often result.

"A mandatory policy of single embryo transfer would be of substantial benefit to the health of Canadian babies while still benefiting infertile couples," the researchers wrote.

In one year at their hospital in Montreal, for example, 75 babies — all either a twin or a triplet conceived with IVF — were admitted to the intensive care unit between 2005 and 2007.

Twenty were born extremely prematurely, six of them died and five had severe bleeding in the brain.

The researchers estimated that if the mothers of these babies had had just one embryo transferred, there would have been just eight babies admitted to the intensive care unit.

Barrington told Reuters Health that multi-embryo IVF is too risky to continue unrestricted, and that being selective about who receives multiple embryos might be one compromise, since chances of getting pregnant for women over 35 who transfer just one embryo are greatly reduced.

Other experts agreed that a rigid one-embryo policy might not be the way to go.

"In my opinion, reproductive endocrinologists have to determine who's the best candidate, instead of mandating it," said Kurt Barnhart, a physician at the University of Pennsylvania's Penn Fertility Care in Philadelphia.

"If you mandate it, there are some people who won't get pregnant at all."