Preemie survival odds improve over 20 years in U.S.

More extremely premature infants born in the U.S. are surviving without major illnesses, but survival of the smallest and youngest remains a challenge, a new study suggests.

Researchers from the U.S. National Institutes of Health reviewed the birth records of more than 35,000 premature infants born from 1993 to 2012 weighing between 401 grams or 14 ounces to 1,500 grams or 3.3 pounds.

Among preemies born at 27 weeks, survival without major problems increased from 29 per cent in 1993 to 47 per cent in 2012. Full term babies are born after 39 to 40 weeks of pregnancy.

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"Although overall survival increased for infants aged 23 and 24 weeks, few infants younger than 25 weeks' gestational age survived without major neonatal morbidity [complications], underscoring the continued need for interventions to improve outcomes for the most immature infants," Dr. Barbara Stoll of Emory University School of Medicine in Atlanta and her co-authors wrote in Tuesday's issue of JAMA.

The researchers said the findings may be valuable in counselling families and developing new treatments.

Stoll called the findings of progress "cautiously optimistic."

The findings were based on hospital records from 26 academic medical centres and may not reflect outcomes at smaller hospitals.

The researchers speculated on reasons for improvements, such as more cesarean section births, which may be gentler for the most fragile infants, better infection control procedures, newer methods to help preemies breathe without using ventilators, and giving women steroids before childbirth to boost lung growth.

An editorial published with the study said while the researchers document important progress over the last two decades, it's clear a substantial number of extremely preterm infants either die or survive with one or more major complications.

"[A]n additional commitment must be made to further improvements in the decades to come," Dr. Roger Soll of the University of Vermont College of Medicine in Burlington said.