There has been no improvement in survival rates for babies born before 24 weeks in the past 10 years, an influential study is expected to announce.
Of infants born at 23 weeks, 40% die on the labour ward and of those that live only 26% survive hospital.
The figures are from a study called EPICure 2, which examined premature births in England in 2006. An improvement was seen in survival rates for babies who reach 24 weeks, when 47% survive, and 25 weeks, when 67% live.
The findings seem to reinforce the existing upper limit for abortions, which currently stands at 24 weeks.
Last October, the Science and Technology Committee of MPs found no scientific justification for lowering the 24-week limit.
This was because survival rates for babies born before this point had not improved since 1995.
Liberal Democrat MP Dr Evan Harris who sits on the committee said: "Our report concluded that while the evidence showed that survival in premature infants born at 24 weeks and above had improved, there was good evidence that below that point - the current abortion time limit - neonatal survival has not changed since 1995."