Preemies treated in high-volume neonatal units more likely to survive

NEW YORK (Reuters Health) - Babies born very early stand a better chance of surviving if they are treated in neonatal hospital units that see a large number of premature infants, a new study shows.

The British study included babies born before 33 weeks of pregnancy who were admitted for extra care. Full term is considered 39 to 40 weeks.

"The first hours of these babies' lives can be crucial, which means it is essential to give them expert care at this time," said lead author Sam Watson, from the University of Warwick's Medical School and Department of Economics in Coventry, in a news release.

The analysis confirms results of a 2010 U.S. study led by Dr. Judith Chung, a maternal-fetal medicine specialist at the University of California, Irvine.

"The best outcomes for high-risk infants occur in hospitals with the highest volume," Chung, who was not involved in the British study, told Reuters Health.

"If you're at an increased risk of premature delivery, you should deliver at a higher level, high-volume hospital," she said.

For the new study, the researchers analyzed data from 20,554 very premature infants delivered at 165 hospitals with neonatal units across the UK. About 4.5 percent of them died in the hospital.

Infants were 32 percent less likely to die if they were admitted to high-volume neonatal units compared to low-volume units, the researchers found.

The earliest preemies, those born before 27 weeks of pregnancy, benefited the most from high-volume units, Watson told Reuters Health.

Those babies had half the odds of dying when they were treated in neonatal units that handle a high number of premature births, compared to low-volume units, the study published in BMJ Open found.

"The effect we observe is mainly being driven by the infants born at less than 27 weeks," Watson said.

"It would be most important to deliver the youngest fetuses at the highest volume hospital," Chung said.

Unfortunately, doctors often cannot predict premature births. But expectant mothers who go into labor prematurely sometimes can and should be transferred, Chung said.

Why babies are more likely to survive in hospitals that deliver more preemies remains an open question, but researchers suspect clinical experience is key.

"It could be a case of the physicians in the high-volume units have more experience and are more skilled," Watson said. "It is also possible that economies of scale play a role, in that the larger and busier units have more resources to invest in technology and facilities."

Chung likened doctors working in neonatal units with a high volume of preemies to cardiac surgeons who perform the highest number of heart surgeries.

"The assumption is it's probably experience," she said. "If you do more of them, you're better."

Neonatologist Dr. Valencia Walker described the study results as "intuitive."

"Anything we get a chance to perfect, we will get better and better at it if we have the resources to do it," she told Reuters Health.

Walker, from the David Geffen School of Medicine at UCLA in Los Angeles, was not involved in the current study.

She pointed out that systems to determine where pregnant women deliver their babies in England and the U.S. differ significantly.

In 2003, the UK created a model of networked, regionalized units to facilitate the transfer of premature babies to higher care neonatal units. The current study highlights advantages of the system but also raises concerns about the possible result of smaller neonatal units closing, Watson said.

Walker said the U.S. has far fewer neonatal intensive care units and a different set of considerations and restrictions regarding transferring patients. In Southern California, for example, traffic can at times render transfers impossible.

Worldwide, 15 million of the 135 million babies born in 2010 were premature - defined as before 37 weeks of pregnancy - and 1.1 million died, according to a United Nations report (see Reuters story of May 2, 2012 here: Since 1995, the average rate of premature births has doubled to 6 percent in developed countries, the report found.

Nutrition, maternal age, smoking, alcohol, obesity and diabetes have all been implicated in premature births.