When Jen found out she was pregnant less than a year after giving birth to twins, she thought the universe was playing a joke on her.

That's because she believed she'd had her tubes tied nearly 11 months earlier when she delivered her baby girls via C-section at Mount Sinai Hospital in Toronto.

"So when I took the pregnancy test and discovered that it was positive, I was honestly just in a state of shock and disbelief for quite a while," she told As It Happens host Carol Off. "I thought that I defied some insane odds."

Then she says she found out the tubal ligation procedure she'd asked for never actually happened — and nobody at Mount Sinai informed her.

So she and her husband Jim have filed an $800,000 wrongful pregnancy lawsuit against the hospital and their two obstetricians, arguing they should be liable for the cost of raising their daughter.

As It Happens is withholding the couple's last name to protect the privacy of their children.

Mount Sinai declined to comment while the matter is before the courts. The couple's allegations have not been proven.

'Children bring joy. They also bring stress'

Jen and Jim already had a six-year-old daughter at home when they welcomed their twin girls into the world in July 2011.

They decided three kids was enough, she says, and Jen opted to have a tubal ligation at the same time as her C-section.

She says she spoke with her doctors at length about the procedure, signed all the necessary consent forms, and booked the procedure.

But when she called her doctor in June 2012 with the news that she was pregnant again, she says he couldn't find any evidence of the procedure on her chart.

Jen and Jim, a Toronto couple suing Mount Sinai Hospital for wrongful pregnancy, have four daughters. (Submitted)

Jen was 39 at the time, with three young children at home, and she didn't want to be pregnant again.

"After several weeks of kind of wrestling, struggling with the decision, I booked a procedure to have an abortion," she said.

But when the time came, she says she just couldn't go through with it.

The couple's fourth daughter was born in February 2013.

"We love her very much," Jen said. "There is joy. Children bring joy. They also bring stress. They bring a lot of expenses."

Hospital denies wrongdoing

The lawsuit, filed in the Ontario Superior Court of Justice, argues "the defendants were negligent in failing to schedule and/or perform the tubal ligation, in failing to realize the tubal ligation was not performed and in failing to advise [Jen] that the tubal ligation had not been performed."

"At the core of a wrongful pregnancy lawsuit like Jim and Jen's is the right of a woman, together with her partner, to make reproductive choices," Tanya Pagliaroli, the couple's lawyer, said in an emailed statement.

"When, as a result of medical error, that right has been infringed, the parents should be fully compensated for all of the costs that flow from that error."

But the hospital disagrees. In a statement of defence obtained by CTV News, Mount Sinai said it "denies that there was any breach of duty want of care or negligence on its part."

In the meantime, Jen and Jim's children don't know anything about the accidental pregnancy or the lawsuit.

"When she is old enough — when they are all old enough — to understand reproductive options and choices, then we will have a conversation around how she came to be in this world," Jen said.

"I'm fairly confident she'll understand."

Written by Sheena Goodyear. Interview with Jen produced by Sarah Jackson.