Doctors and parents having to make life and death decisions about the treatment of very premature babies will now have better information thanks to an online calculator that can tell more than just how long the infant was in the womb.

The online calculator bases its decisions on a study led by University of Texas Medical School at Houston researchers who found factors such as weight and gender also strongly influence outcome when babies are at the fringes of viability.

“This was born of some degree of frustration that we can’t give these parents a better sense of their baby’s chances. At such sensitive times, it’ll mark a significant improvement to be able to share evidence-based data about how infants on average fare,” said Dr. Nehal Parikh, a University of Texas Medical School at Houston professor of pediatrics and one of the study’s author, according to the Houston Chronicle.

The researchers studied 4,446 infants born 22 to 25 weeks after conception. A full-term pregnancy lasts 40 weeks. About 15,000 such babies are born annually and they require aggressive intensive care to survive. According to the study’s findings, 49 percent of the infants in the study died and 21 percent survived without disability based on tests done when they were about two years old.

“We found that bout 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,” Jon Tyson of the UT-H, who led the researchers, said.

The study also found that, besides gestational age, birth weight and sex, there were other factors which influenced these babies’ chances of survival, such as whether the mother received prenatal steroids to help fetal lungs mature and whether the infant was a single delivery rather than one of twins or more.

How did sex and steroids influence the survival rate? Well, according to the study, a 24-week-old two-pound male twin whose mother did not receive steroids has survival odds of 69 percent and a 50 percent chance of having a severe impairment. A female twin the same age and weight has survival odds of 86 percent and a 23 percent chance of severe impairment.

Moreover, the study found that a week more or less spent in the mother’s womb and the sex of the baby could tell a lot about chances of survival. For example, a girl at 23 weeks could be as strong as a boy at 24.

Based on these findings, published in the April 17 New England Journal of Medicine, the National Institute of Child Health and Human Development, which funded the study, created a Web site that outlines the odds of healthy survival in specific cases. This way, physicians and parents may access an online tool that generates statistics, based on the factors the researchers listed in their article.

“The researchers' findings, and the tool they developed, provide important information that physicians and family members can consult to help them make the most informed treatment decisions possible,” Dr. Duane Alexander, director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development said.