WEST FARGO (AP) - When their youngest children were born, Trevor and Kelley Lehfeldt could slip wedding rings on the tiny babies' ankles and arms.

Their quadruplets arrived Jan. 16, 2005, nearly four months too early. The largest, Jonah, weighed 1 pound 11 ounces; the smallest, Lilley, weighed under 1 pound 7 ounces.

At the time, doctors told Kelley and Trevor that their children had a one-in-five chance of surviving.

Lance, Keaton and Lilley beat those odds. Today they are 2-year-olds who live in West Fargo with their parents and older siblings. Their brother, Jonah, died in May 2006.

Like many babies born too early and too small, all the Lehfeldt quads have faced significant challenges in their young lives.

Their mother estimates that among the four children, they've had more than 30 surgeries at various hospitals across the Midwest to address everything from bleeding in the brain to vision difficulties to heart conditions. Medical bills, much covered by insurance, have crept into the millions.

"I wouldn't give them back, but I wish they didn't have problems," Kelley said, cuddling Lilley close to her.

Advances in medical care have greatly improved the outlook for babies born too early and too small. Sometimes called "micro preemies," the babies arrive after less than 26 weeks in the womb and weigh less than 2 pounds. Full-term births occur as early as 37 weeks.

Micro preemies have the necessary organs for life. But until the lung's air sacs develop, which usually happens at about 24 weeks, it's difficult for technology to keep a baby alive, said Dr. Scott Mutchler, director of the Neonatal Intensive Care Unit at Innovis Health in Fargo.

It's more common for multiples to arrive early, but sometimes there's no known reason for a premature delivery, Mutchler said. When the tiny babies are born, they face months in the NICU. Even when they leave, their challenges may linger.

Mutchler estimates that 30 percent of babies who weigh less than 2 pounds at birth will have long-term difficulties, including asthma, digestive issues or problems with mobility. The NICU doctor calls himself an optimist.

"I like to think a large number of them will turn out OK," he said.

The Lehfeldt quadruplets, conceived with the help of fertility drugs, were born at 24½ weeks. Their footprints were the size of decorative stamps that might border a baby announcement.

"I had been feeling funny all day," Kelley Lehfeldt said.

Keaton, Lance and Lilley spent 103 days in MeritCare's NICU. They came home April 28, 2005.

Jonah remained in the hospital until he was more than a year old. In January 2006, he joined his siblings at home but still breathed through a tube in his neck.

In May, that tube fell out. His parents and paramedics revived him, but not before the baby suffered severe brain damage.

"It was the hardest, but easiest, decision to pull out his trach," said his dad, Trevor. "We knew there was no brain activity."

For the other Lehfeldt quads, their short lives have been a roller coaster of setbacks and promising milestones.

Trevor and Kelley were given the worst-case scenario when their quadruplets were born. Doctors told them their children could be deaf or blind, face learning disabilities or be in a wheelchair.

Today Lance and Keaton walk and talk. Their parents no longer lug oxygen tanks and monitors when they leave the house.

"It's nothing short of amazing," says their mother.

Still, all three children have struggled with some of the challenges the earliest preemies can face, said their MeritCare pediatrician, Dr. Christopher Tiongson. As a result, it's been hard for them to match their peers developmentally.

"It's hard to catch up when you're fighting so hard to hang even," he said.

And caring for the children is an exhausting and overwhelming responsibility.

Trevor and Kelley are both employed by the U.S. Postal Service. They work different shifts so one of them can be home at all times. As a result, they seldom see each other.

Each week 10 or more therapists and others work with Lance, Keaton and Lilley. The rotation is so common that Kelley and Trevor hardly notice when people come and go.

"They're extended family now," Trevor explained.

The family also has received support from others, including members of the Red River Valley Mothers of Multiples group, who provided meals and advice for the family.

Lilley doesn't fully sit up, talk or crawl yet. A shunt drains fluid off her brain. She's undergone four eye surgeries. Her parents hope someday a contact lens will help her see a distance of 5 feet with her left eye.

Meanwhile, her brothers try to keep up with their older sister, Tanna, who is 5 and loves to mother them. Lance is still susceptible to colds and respiratory infections, his mom said. She also worries about his heart, which had a hole in it until surgeons repaired it about a year ago.

The Lehfeldts don't know whether Keaton will have normal vision.

Still, their pediatrician says the children are making progress.

"You never know what things a preemie will dodge and what they will have to climb over," Tiongson said. "At this point, we're looking for them to settle in and not go from crisis to crisis, but to build on a period of better health."