CHICAGO — One is a healthy first-grader, the other an honors college student majoring in psychology. Once the tiniest babies ever, both are thriving, despite long odds when they were born weighing less than a pound.

A report from the doctor who resuscitated them at a suburban Chicago hospital is both a success story and a cautionary tale. These two are the exceptions, and their remarkable health years later should not raise false hope: Most babies this small do poorly; many do not survive even with advanced care.

'These are such extreme cases,' said Dr. Johnathan Muraskas of Loyola University Medical Center in Maywood, Ill. They should not be considered 'a benchmark' to mean that doctors should try to save all babies so small, he said.

The report involves Madeline Mann, born in 1989 weighing 9.9 ounces, then the world record; and 7-year-old Rumaisa Rahman, whose 9.2-ounce birth weight is the world's tiniest. Two other babies born since 1989 weighed less than Madeline; a German girl was born last year at the same weight.

The report, released online Dec. 5 in Pediatrics, addresses a question that was debated when Madeline was born

and has no answer: 'What is the real age of viability? No one knows,' said Dr. Stephen Welty, neonatology chief at Baylor College of Medicine and Texas Children's Hospital in Houston.

Muraskas and the report's co-authors said most newborn specialists consider babies born after 25 weeks of pregnancy to be viable — likely to survive — and so they should receive medical intervention if necessary to breathe. Younger babies are generally in a 'gray zone,' where intervention isn't so clear-cut, the report suggests.

Dr. Edward Bell, a University of Iowa pediatrics professor, estimates that about 7,500 U.S. babies are born each year weighing less than 1 pound, and about 10 percent survive.

Muraskas said his report shows a sometimes overlooked fact: gestational age is more critical for survival than size.

Rumaisa and Madeline were

the average size of an 18-week-old fetus, but they were several weeks older than that. Their gestational ages — almost 26 weeks for Rumaisa and almost 27 weeks for Madeline — meant their lungs and other organs were mature enough to make survival possible. Both required intensive medical intervention. They were delivered by C-section more than a month early because their mothers developed severe pre-eclampsia.

Both babies were hooked to breathing machines with tubes as slender as a spaghetti strand slipped down their tiny airways.

Madeline has asthma and remains petite — 4-foot-8 and about 65 pounds at 20; Rumaisa at 5 weighed 33 pounds and was 3.5 feet tall, smaller than about 90 percent of kids her age.

Madeline is 22 and a senior at Augustana College in Rock Island, Ill.; Rumaisa is 7 and a first-grader near Chicago.

Jim Mann, Madeline's father, said that other than asthma, the only lasting effect his daughter has mentioned is having trouble finding age-appropriate clothes because she is so small.