Early next year, Barbara Ann Carroll is going to try her very best to get pregnant.

Having already endured three fruitless attempts at in vitro fertilization, the 44-year-old postmaster from Sainte-Adèle, Que., is hoping that eggs donated by the daughter of a friend will help her fulfill her dream of being a mother.

Ms. Carroll was already in a hurry to conceive because of her age, but now she has another reason to make haste. The majority Liberal government last week tabled a bill that would make it illegal for women over the age of 42 to undergo IVF.

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Quebec's proposed age limit is just one part of a dramatic curtailment of the province's publicly funded assisted procreation program, but the change is reigniting the debate about a classic motherhood issue: How old is too old to give birth?

"They just don't want to spend money for that. I understand that. But let me pay for it. Don't punish me," Ms. Carroll said, her voice cracking. "The only ones that can understand this are the ones that live it."

The province would fine doctors as much as $50,000 if they perform the procedure on patients older than the threshold or direct those patients to co-operative IVF clinics outside the province.

Supporters of an age limit say society has an interest in discouraging older women from trying to pursue motherhood because they and their babies are likelier to have medical complications for which the public health-care system is ultimately responsible.

"There is a clinical risk," Gaétan Barrette, Quebec's Health Minister, said in an interview with The Globe and Mail. "When you are a government and you pass bills, you have to consider patient safety. We are there to minimize the risks to the patient."

Fertility doctors and advocates say the government has no business forbidding women over 42 from having IVF in Quebec if they want to pay for it themselves, especially if they use a younger donor's eggs, a practice on which the proposed legislation is silent. It is not known yet when the bill will pass or take effect.

While some countries refuse to pay for IVF for older women, few, if any, ban it after a particular age.

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"In Quebec, I can understand the government saying, 'We don't want to pay for treatment if you're over 42 and you're using your own eggs.' I get that," said Neal Mahutte, a Montreal fertility doctor and president of the Canadian Fertility and Andrology Society. "But to say we won't allow you to do fertility treatment doesn't make sense to me."

For the past four years, Quebec has had one of the most generous assisted procreation programs in the world.

In 2010, after a public campaign by megastar Céline Dion and TV personality Julie Snyder, both of whom conceived their children through IVF, Jean Charest's Liberal government allowed virtually unlimited coverage for IVF. (Ms. Snyder is the long-time partner of Pierre Karl Péladeau, the former media baron running for the leadership of the Parti Québécois.)

The goal was to help infertile couples conceive and reduce the number of twins and triplets by requiring doctors to implant just one embryo in most cases.

Quebec's multiple birth rate among women who had assisted reproduction declined from 38.5 per cent in 2009-10 to 17.2 per cent in 2012-13, according to a June report from Robert Salois, the province's Health and Welfare Commissioner.

But the savings did not make up for Quebeckers' enthusiastic uptake of IVF, the cost of which ballooned from $16.4-million in 2010-2011 to $80.8-million in 2012-2013, the report found. The bill tabled last Friday would replace public insurance coverage with a limited tax credit.

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The science is clear that a woman's fertility and her odds of conceiving through IVF decline as she ages.

The live birth rate for Canadian women pursuing IVF with their own eggs is 16.3 per cent at age 40. It falls to 11.8 per cent at 41, 7.6 per cent at 42 and 4 per cent at 43, according to data from the Canadian Assisted Reproductive Technology Register (CARTR), which includes information provided voluntarily by nearly all the country's fertility centres.

The story is different if the eggs come from a younger donor, which is legal in Canada if the donor is paid no more than her expenses.

The live birth rate for Canadian women over 40 using donated eggs is between 33 and 38 per cent, and does not fluctuate much with the carrying woman's age.

Shauna Lussier, 44, gave birth six months ago to healthy twins, Brynlea and Coltan, using a donor's eggs. The Winnipeg government employee and her husband, Dominic Lussier, travelled to the Czech Republic for the $8,000 procedure after a miscarriage and unsuccessful fertility treatments in Canada.

Ms. Lussier does not feel limited by her age. She is healthy, secure in her career and better prepared emotionally to raise her twins than she might have been at a younger age, although she had not intended to start her family in her 40s.

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She was saddened to hear of Quebec's plan to ban IVF for women like her.

"When you want to have a family and you have the disease of infertility, it would be like saying to a 65-year-old cancer patient, 'You're too old to have the treatment,'" she said. "I can't imagine how heartbreaking that would be, to have their government not support them to have a family."

The Canadian Fertility and Andrology Society, which represents the country's fertility doctors, does not have an age limit in its guidelines for IVF.

In March of last year, the American Society for Reproductive Medicine's ethics committee updated its guidelines for egg donation, saying that healthy women up to the age of 54 could be candidates for the procedure.

Just because some older women can be candidates for IVF does not mean they should be, said Françoise Baylis, who holds the Canada Research Chair in Bioethics and Philosophy at Dalhousie University in Halifax.

"I think in this case what makes it complicated is that the state, arguably, could be bearing the consequences of some of these decisions," she said. "We do know that with older women, in terms of pregnancies, there are increased complications for that pregnancy."

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Compared with women aged 20-34, women over the age of 40 have a 50-per-cent higher risk for developing gestational hypertension, pre-eclampsia and placental abruption; they have an 80-per-cent higher risk of delivering by cesarean section, according to Canadian Institute for Health Information figures provided at the request of The Globe.

In 2012-13, over-40 mothers cost the Canadian health-care system 11-per-cent more than the 20-34 group, CIHI said.

Gloria Poirier, the executive director of the Infertility Awareness Association of Canada, pointed out that Quebec would still bear those costs if older women skirt the law, undergo IVF outside the province, and return to give birth.

"I think [the age limit] is going to encourage cross-border and international medical tourism," she said. "In order to improve their chances of success, they're going to have multiple embryos [transferred] which, when it does work, often results in multiple births. So then they come back to Canada and they have twins or triplets and that is not a good thing."