When the time comes for six-week-old twins Gavin and Gabriel Hansen to be put to bed, their mother bundles them together in a single blanket. They sleep better that way, she says, because that's what they learned in the womb. But it was that same closeness that almost killed them both before they saw daylight.

"I never realized how worried I could get," Hansen said. "It was devastating. We were so hopeful about the twins."

Hansen's pregnancy started off smoothly, if not without a little surprise. At eight weeks, she got the news that there were two lives incubating inside of her.

"It was exciting," she said.

But the thrill wouldn't last long. At 15 weeks, doctors told Hansen that signs of TTTS were showing up in the twins. The problem occurs in about 15 percent of pregnancies involving identical twins. When accidental connections form between vessels that provide nutrients to each of the babies, they cause blood to divert from one to the other. Left untreated, the condition threatens the lives of both babies and can be fatal about 90 percent of the time -- something doctors continually reminded Hansen.

"It was just a lot to take in," she said. "Every time we went [to the doctor], it got a little bit grimmer."

Hansen's husband, Christopher, said he felt the same despondency during appointments.

"It got to the point where they'd say, 'When you come back, there's a good chance one of them won't be alive,' " he said.

That's when the Hansens met with Dr. Michael Ball and Dr. Michael Belfort of St. Mark's Hospital's maternal-fetal medicine team in Salt Lake City. The doctors explained a rare new procedure that would use a laser to ablate, or shut down, the connections between the babies. The physicians are two of only a handful of specialists in the country who can perform the operation. To date, they've performed 17 such surgeries across the country, 10 of them in Utah.

"Her babies were at real risk," Belfort said. He said he only recommended the surgery because the syndrome was advancing rapidly and the Hansens' situation was dire. The risks -- like tearing the membrane between the twins -- are only justifiable in severe cases, and even if the surgery is performed perfectly there's a 10 or 15 percent chance there will still be complications, Belfort said.

"Sometimes you can do everything correctly, but once you disconnect the two babies the pressures are just too much for one or both of their hearts," he said. "It's much more technically demanding and has a much higher risk. You're essentially trying to paint a ceiling through the front door."

Because the problem was developing so quickly, the doctors told Hansen she had 24 hours to decide. Gabriel was taking on too much fluid and had some in his lungs. Gavin wasn't getting enough; he was anemic, and his bladder and kidneys didn't even show up on ultrasounds anymore.

Faced with the almost certain loss of her boys if she did nothing, Hansen made the choice and was on an operating table within 48 hours.

"That was kind of a shock, to have to make our decision so quickly," she said. "It seemed like I had just barely been pregnant."

The procedure is done by making a 3-millimeter incision in the mother's abdomen and inserting a fetoscope with a camera into the uterus. Once the camera finds the connections -- which are often hard to discern among the healthy veins and arteries, Belfort said -- a laser shuts them down one by one.

Hansen's procedure took about two hours. It went about as well as it possibly could have, and when it was done the benefits were immediate, Belfort said.

"There was a remarkable turnaround after the surgery," he said. "It was better than we expected."

The kids started to grow normally after that, Gabriel remaining the bigger of the two. Even when things began looking better, the doctors reminded the parents they weren't completely out of the woods.

"The doctors still just let us know that there were plenty of things that could happen," Christopher Hansen said.

Janis Hansen was put on bed rest for the duration of the pregnancy -- a crawling four months, including Christmas, with not much to do but sit and worry about the health of the kids. As a nurse by trade, thoughts of what could go wrong were amplified in her mind as time passed.

"It's the curse of the nurse," she said. "January was the longest month."

Finally, the babies were ready to come out. As a consequence of the laser surgery, Hansen's uterus had stretched and only a strategically placed stitch was holding the boys in. But at 34 weeks, they could wait no longer. Christopher and Janis Hansen rushed to Timpanogos Regional Hospital, where a team of 18 doctors, nurses and other attendants helped deliver the babies by Caesarean section. Gavin came out first. He was followed by his now younger brother, Gabriel, two minutes later.

Janice Hansen recalled the feeling when she first heard Gavin cry, vindicating the months of suffering and worry she had endured.

"You just don't know until they're born," she said. "For so many months, we worried about them."

Christopher Hansen said he went immediately to the babies, making sure they were OK.

"The first thing I was doing was counting fingers and toes," he said. "They were all there."

Because of the premature timing of the births, the twins spent about five weeks at the hospital while doctors watched over their development for further problems. Dr. Dale Gerstmann, the twins' physician while they were in Timpanogos Regional Hospital, said although he dealt with the typical concerns that all premature babies bring, like underdeveloped respiratory systems and oral muscles for feeding, he never had reason to fear for the twins' lives. He attributes a big part of that to the in-utero surgery.

"The best thing I can say is that it was totally usual," he said. "We didn't have to give any special attention to specific problems."

Now that the boys are home, Hansen says she's dealing with the late nights and constant crying and feeding she didn't see while they were in the hospital -- but she doesn't mind. She's just happy to be a mom. And as for whether she thinks Gavin will hold a grudge against his younger brother for stealing all his nutrients -- well, that probably won't be an issue, she said.

"I think it's just a quality that he has," she said. "He's very giving."