The survey of premature infants in the Trent region found that the survival rate of those born at 24 or 25 weeks of gestation improved from 36 percent of those born between 1994 and 1999 to 47 percent of those born between 2000 and 2005, The Independent reported. However, there was no significant improvement for those born at 23 weeks and none of those born at 22 weeks survived.

Anti-abortion members of Parliament want to cut the current 24-week time limit on abortions as part of the Human Fertilization and Embryology Bill. Some are pushing to ban second-trimester abortions, while others would settle for 20 weeks.

They argue that the limits of viability have been pushed back. But David Field of the University of Leicester, who led the study, said he believes it shows the opposite.

"The limits of viability for the survival of premature babies have been reached," he said.