US researchers found premature baby’s fate may be influenced by four factors beyond gestational age. Based on all these factors, one may determine whether an extremely premature baby will survive and grow up healthy or not.

Weight is the first factor which influences premature baby’s life. Babies that weight more survived premature birth better. Then, babies that do not have a twin are more likely to survive premature birth and to have a healthy life than the others. The treatment with steroids is the third factor which influences babies’ life. Those whose mothers went through a steroid treatment to hasten the development of the lungs survived premature birth better, the researchers reported in the New England Journal of Medicine.

“Using the five factors in combination really gives you a better idea of how children are going to do, rather than singling out a single factor,” Dr. Rosemary Higgins of the National Institute of Child Health and Human Development (NICHD), who worked on the study, said in an interview for Reuters.

The researchers, led by Jon Tyson of the University of Texas Medical School at Houston, studied 4,446 infants born 22 to 25 weeks after conception. A full-term pregnancy lasts 40 weeks. 49 percent of the infants in the study died and 21 percent survived.

“We found that about half of the infants survived and that about half of those who survived had neurodevelopmental impairments. This is a very, very high risk group of babies,” Tyson said in a statement.

“There clearly appears to be a biologic difference that gives girls a week advantage over the boys for the same gestational age. It's a difference that's unexplained,” Higgins said.