Results of the study, published Wednesday in The New England Journal of Medicine, are likely to influence a discussion taking place among professional medical associations about how to counsel parents and when to offer treatment to such tiny babies.

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A new study of thousands of premature births found that a small minority of babies born a week or two before what is now generally considered the point of viability can be treated and survive, in some cases with relatively few health problems.

While the babies’ odds of success are long, the study nonetheless is likely to intensify the agonizing decisions that parents and doctors face about whether to actively treat a child born as early as 22 weeks into pregnancy.

The study, one of the largest and most systematic examinations of care for very premature infants, found that hospitals with sophisticated neonatal units varied widely in their approach to 22-week-olds, ranging from a few that offer no active medical treatment to a few that assertively treat most cases with measures like ventilation, intubation and surfactant to improve the functioning of babies’ lungs.

“It confirms that if you don’t do anything, these babies will not make it, and if you do something, some of them will make it,” said Dr. David Burchfield, the chief of neonatology at the University of Florida, who was not involved in the research. “Many who have survived have survived with severe handicaps.”

Results of the study, published Wednesday in The New England Journal of Medicine, are likely to influence professional medical associations about how to counsel parents and when to offer treatment to the babies.

The findings may also have implications for the abortion debate. The Supreme Court has said states cannot ban abortion before a fetus is viable outside the womb, and 24 weeks has generally been cited by medical experts as the time of viability.

Recently, physicians who work with very premature infants have begun to consider it reasonable to offer active treatment for babies born at 23 weeks. A 2014 summary of a workshop that involved the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics said “in general, those born at 23 weeks of gestation should be considered potentially viable” as more than a quarter of them survive if treated intensively.

The report said nothing helps babies less than 22 weeks old to survive.

But babies born between 22 and 23 weeks are a question mark, their survival chances slim but varying by things like birth weight and whether the mother received treatment before delivery with corticosteroids.

About 18,000 very premature babies are born annually in the U.S., with about 5,000 at 22 or 23 weeks.

The study, involving nearly 5,000 babies born between 22 and 27 weeks gestation, found that 22-week-old babies did not survive without medical intervention. In the 78 cases where active treatment was given, 18 survived, and by the time they were young toddlers, seven of those did not have moderate or severe impairments. Six had serious problems such as blindness, deafness or severe cerebral palsy.

Of the 755 babies born at 23 weeks, active treatment was given to 542. About a third of those survived, and about half of the survivors had no significant problems.

Dr. Carl T. D’Angio, director of neonatal clinical research at University of Rochester Medical Center, who was not involved in the study, said his center decided several years ago to offer active treatment to 23-week-old babies, and that many sophisticated neonatal units are doing the same.

At 22 weeks and five days into pregnancy, Rochester offers corticosteroids to mothers, hoping the drugs can have 48 hours to work before delivery at the 23-week mark. But for 22-week-olds, he said, “we don’t have enough to offer the babies to really offer them a reasonable chance of survival.”

As techniques for keeping babies alive improve, parents face wrenching choices that are sometimes based on whether the estimated age is 22 weeks and one day or six days. Indeed, the study found that hospitals tend to “round up,” with babies closer to 23 weeks more likely to receive treatment.

But the authors and other experts also noted that gestational age is an educated guess, based on women’s recollection of their last menstrual period and estimated fetal size. Other factors, including prenatal care and the fact that girls are often a week more mature than boys, should also influence decisions, experts say.

The study, which evaluated cases at 24 hospitals in a neonatal network supported by the National Institute of Child Health and Human Development, found that four hospitals intervened for no 22-week-olds, five intervened for all 22-week-olds and the rest varied.

In all, about a fifth of the 357 babies that age were treated. The reasons could include family preferences and hospital policy.

“We can’t really say whether the differences revolve around differences in values, that for some physicians or parents the risk of impairment might outweigh the decision for treatment,” said Matthew Rysavy, a medical student at the University of Iowa, who led the study with Dr. Edward Bell, a pediatrics professor there. At Iowa, Bell said, treatment is offered to most 22-week-olds and he considers 22 weeks a new marker of viability.

“That’s what we think, but this is a pretty controversial area,” Bell said. “I guess we would say that these babies deserve a chance.”

He pointed to Chrissy Hutchinson, 32, of Manchester, Iowa, as a success. Her water broke in 2010 when she was 21 weeks, six days pregnant. The first hospital she went to said there was no survival chance.

The Hutchinsons called the University of Iowa, and at 22 weeks and one day, 1.1-pound Alexis was delivered. Alexis was treated and stayed in neonatal intensive care for almost five months. Now, Hutchinson, a pharmacy technician, said, aside from being more vulnerable to respiratory viruses, Alexis is a healthy 5-year-old.

Some of the study’s results suggest that among 22-week-olds who are treated, experiences like the Hutchinsons’ would be exceedingly rare because she delivered so close to 22 weeks and did not have time for corticosteroids beforehand.