Baby boxes — a convent practice that dates to medieval times — are seeing a revival around the world, including in Canada where Alberta became the second province on Monday to offer the safe haven for unwanted infants.

Alberta's Covenant Health, a Catholic-run health-care provider, opened baby boxes in two Edmonton hospitals: Grey Nuns Community Hospital and Misericordia Community Hospital.

The Alberta service comes three years after Vancouver's St. Paul's Hospital brought the 12th century idea to Canada in May 2010.

Three months after opening its so-called angel cradle, a two-day old baby was left in the bassinet at St. Paul's, accompanied by a paper listing the date of birth, ethnicity and family history. No other child has been left there since.

Here are frequently asked questions about the concept of baby boxes, their use around the world and how they work.

How does the 'angel cradle' system work?

Baby boxes are known by many names around the world, including baby hatches, foundling wheels or newborn safe havens. All three Canadian hospitals using the system refer to their baby boxes as angel cradles.

Around the world, baby boxes are often located along the exterior of a hospital or church so a mother can anonymously leave a baby in it.

The three Canadian angel cradles operate in a similar way. A three-foot-tall door that opens at waist level is located in an inconspicuous area near the emergency department.

In Edmonton, the half-sized door opens to reveal a bassinet outfitted with a blanket and a teddy bear. An alarm goes off 60 seconds after the door opens, alerting a nurse in the triage area to a potential delivery.

Using a "digital peephole" — a camera that looks into the bassinet — the nurse ensures that someone's left an infant and not something else. The peephole also allows the nurse to make sure the mother is no longer present, ensuring the hospital won't infringe upon the promise of anonymity by opening the door while the mother is still standing there.

Once the area is clear, the nurse opens up an internal door to access the bassinet and brings the baby into the hospital where it undergoes a medical check. The child is then handed over to Alberta's Human Services ministry for adoption.

Where did the idea come from?

Until the early 20th century, convents used foundlings wheels, a wooden cylinder built into the wall where mothers could lay their babies inside, then rotate the wheel to bring the child inside the structure. Mothers would then ring a bell to alert the nuns to the child's presence.

High-tech hospital baby hatches like this one in Rome, which features a heated crib, are replacing the foundling wheels once used by convents in the city. (Tony Gentile/Reuters)

It is believed that Europe's first baby hatch opened in Rome in 1198 under Pope Innocent III, who was frustrated by the number of abandoned newborns found floating in the Tiber River. Most closed in the 19th century with the introduction of modern health-care services.

In Canada, all three baby boxes are operated by Catholic organizations. The two Edmonton hospitals that opened baby boxes on Monday are run by Covenant Health, which describes itself as Canada's largest Catholic health-care organization.

St. Paul's Hospital, home to the inaugural Canadian baby box, is run by Providence Health Care.

Why allow baby boxes?

Proponents of the baby box say that the anonymous drop-off can prevent infanticide or dangerous abandonment of babies.

At the opening of the B.C. angel cradle in 2010, Dr. Geoff Cundiff, head of the department of obstetrics and gynecology, said that nearly once a month a woman giving birth in the hospital left her child at the facility. He worried about the infants who were left in dumpsters or worse.

Baby boxes enjoyed a revival in Europe in the 1990s after a rise in the number of newborns who were abandoned or found dead.

There are currently no studies that prove that the creation of baby hatches has reduced the rate of infanticide or infant abandonment.

Opponents argue that the anonymous dropoff locations violate a child's right to know their biological parents' identities and could put the infant in medical jeopardy since doctors won't know the infant's medical history.

In 2012, the UN Committee on the Rights of the Child called for a ban of the practice of using baby hatches in Europe. The committee said it violates Article 7 of the UN Convention on the Rights of the Child, which says children must be able to identify their parent.

A member of the committee told BBC that baby boxes are a throwback to the past that send a "mistaken message" to pregnant women that they are right to abandon their babies.

In unveiling its new angel cradles, Alberta's Convenant Health countered the UN concerns about baby boxes.

"We recognize that unsafe abandonment still occurs in our society, and this preventative measure at least gives a child a chance to know its history and be reunited if later the parent(s) come forward," Gordon Self, Covenant Health's vice-president of mission, ethics and spirituality, said in a press release.

How prevalent are baby boxes?

Today, the concept is used around the world.

Baby boxes enjoyed a revival in Europe in the 1990s. (iStockphoto)

Germany resuscitated the idea in Europe in 2000 with the establishment of what it calls babyklappes. More than 90 baby-box locations now exist.

Studies suggest that more than 200 baby boxes have been installed across Europe in the past decade alone. More than 400 children have been abandoned in the hatches since 2000.

Other European countries offering baby hatches include Switzerland, Poland, Czech Republic, Hungary, Italy, Austria, Latvia, Belgium, the Netherlands and the Vatican City. The United States, Pakistan, the Philippines, India and South Africa also have baby boxes.

In Japan, a baby hatch called Stork's Cradle was set up in 2007 at Jikei Hospital in Kumamoto City. Eighty-one children were placed in its care over the next five years.

Isn't it illegal to abandon a child?

Under Canada's Criminal Code, anyone who unlawfully abandons a child under the age of 10 so that its life is likely endangered or its health is put into jeopardy can be charged with child abandonment.

After the creation of B.C.'s Safe Cradle program, Vancouver Police said they wouldn't charge mothers who left infants at the hospital baby box because it wouldn't be considered unsafe abandonment. However, charges would apply if the baby showed signs of mistreatment.

Fifty U.S. states have created newborn safe haven or so-called Baby Moses laws to legally protect parents who abandon their children at sanctioned safe havens.

The state laws differ in what is considered a safe haven. Some states include 911 responders as well as fire and police departments in the sanctioned safe haven list, and almost all include hospitals. The laws often specify that the children must be infants born anywhere from within the first 72 hours to up to 30 days.

There are few statistics about child abandonment. In the U.S., the last time nationwide figures were collected on the topic, according to a 2005 University of Vermont study, was in 1998, when about 17,400 infants were reportedly illegally abandoned by being left in dangerous locations or in hospitals.

No known cross-country statistics are kept in Canada.

Saskatchewan's Ministry of Social Services said there have been five cases of infant abandonment in the past five years. Provincial officials in Manitoba said it's rare, with just one case of child abandonment every few years.

New Brunswick and Nova Scotia officials said they haven't had a reported case of child abandonment in the past five years.

The Ontario ministry of children and youth services said it doesn't track such cases.

A spokesperson for B.C.'s ministry of children and family development said infant abandonment is "extremely rare."