HALIFAX - Doctors are closely monitoring a rare set of quadruplets born a week ago, saying two of the babies are suffering from serious lung complications that are threatening their survival.

Dr. Michael Vincer, who helped in the delivery on Jan. 24 at the IWK Health Centre, said the two identical boys are the weakest of the four, with at least one suffering from a significant premature breathing condition.

"He has very major respiratory failure at the moment," Vincer, a neonatologist, told reporters as the babies' parents looked on. "He's still critically ill and we have our concerns about survival."

All but one of the boys - Ben and Alexander - and the two identical girls - Morah and Julia - required breathing tubes when they were born at 29 weeks gestation, all weighing around three pounds each.

Only Julia has had her tube removed, is breathing on her own and has taken small amounts of food. The two boys remain hooked up to special high-frequency ventilators because of their respiratory problems.

Their parents said they are eager to get their babies home to Greenwood, N.S., but understand that it will likely be months before any of them are able to leave.

Christa MacKinnon, 29, said she had held only one of the babies for the first time Wednesday night, adding that there are so many tubes and lines of tape feeding into them that they're difficult to see.

"It was amazing," she said, sitting in a wheelchair and holding her husband Joe's hand. "I'm looking forward to being able to hold the others as well."

The parents said they have been gearing up for the return of the babies to their small three-bedroom home, which has undergone a series of renovations to accommodate the four additions.

Joe MacKinnon, a 36-year-old captain at 404 Maritime Patrol and Training Squadron at 14 Wing Greenwood, said he has been converting the living room into a bedroom and estimating how much it might cost to care for the quadruplets.

He said after adding up the expenses for diapers, food, formula and clothes based on what they spent on their two-year-old son Matthew, he came up with a cost of $28,000 a year.

He said they've organized a fundraising campaign to help out with the future expenses, but he's focusing more on the babies' health and ensuring they thrive.

"I look forward to the times ahead," he said. "But I'm very much a realist right now in that I take those small little victories they have as they get better in the incubators."

Christa said her mother has moved in to help with the care of the babies, who she said look so similar that she can't really tell them apart.

The babies, which were conceived through IVF, are a rare medical phenomenon because only two embryos were injected and both split to develop into identical twins. Chances of that happening are about one in 70 million.

"I've never heard of it before," said Vincer, who's seen three sets of quadruplets delivered at the hospital. "To have two implanted embryos both succeed and then both split that would have to be very, very uncommon."

He said the babies, who are being fed through feeding tubes and intravenous, will have to be monitored to see if they develop any of the chronic conditions that can afflict premature, small babies.

Doctors will screen for cerebral palsy, neurological problems, adequate growth, and language and cognitive delays.

The young mother said she realized it was possible she would have more than one baby, but admitted she was stunned to learn last August that she was having four.

"How can that be possible?" she said.

"It was just really overwhelming all at once to find out that not only were you pregnant ... but, 'Wow, now there's four.' So, it took a little time to let that settle."

Vincer said the caesarean delivery, which began at around 10 a.m. on Jan. 24, was like a highly organized stage play with the doctor co-ordinating a team of about 21 specialists in the operating room as the babies were delivered within three minutes.

"It was a bit like a relay, bringing one baby to the overhead warmer and another baby to an overhead warmer," he said.