Gestational age is not the only factor to affect the survival and disability risk of extremely premature infants, researchers have revealed.
Gestational age has long been used to predict whether an extremely low-birth-weight infant survives and thrives, but the team has identified four other factors that may help in predicting the infants survival.
The four factors that may affect an infant's outcome includes birth weight, gender, whether the baby is a twin and whether the mother was given antenatal steroid mediation to aid the baby's lung development.
The investigators analysed the health records of 4,446 children born between 22 and 25 weeks of pregnancy and weighing between 401-1,000 grams, about one to two pounds at birth.
They further examined the factors apart from gestational age that may influence the outcome with the help of a tool called an outcome estimator.
The findings revealed that an infant's possibility of survival without disability were enhanced if they were of older gestational age, their mothers had been given antenatal steroids, they were female, were singletons rather than part of a multiple birth and they had higher birth weight.
"There is a grey zone of survivability at different gestational ages, and it is impossible to predict the outcome with perfect accuracy, but these new statistical tools are a tremendous aid to us as physicians, particularly when counselling parents faced with agonizing decisions for their extreme preemies," said Dr Mark Mercurio, Associate professor of pediatrics at Yale School of Medicine, attending neonatologist at Yale-New Haven Hospital and chair of the Pediatric Ethics Committee.
"We are able to give parents a better idea of what the child's chances of survival are, and in many cases we defer to the judgment of informed parents," he added.
The report appears in New England Journal of Medicine by a consortium of researchers in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Neonatal Research Network.
The 19-center network includes Yale School of Medicine and Yale-New Haven Hospital.