Just a week before the House of Commons is projected to debate the time limit on abortion in the United Kingdom, a study has been released that indicates that over the past 12 years, no improvement has been seen in the survival rates of babies born before 24 weeks gestation, the current legal limit for abortion in the country. According to the authors of the study, published on BMJ on May 9, 2008, this indicates that a limit has been reached for the survival of premature babies.

Some advocates claim that the current time limit for abortion should be lowered because continued improvements in medical care could contribute to increased survival of preterm babies. That said, this has not been confirmed by scientific evidence. To help understand the effects of medical advances on very premature babies, Professor David Field and colleagues from the University of Leicester observed the survival of all babies born before 26 weeks of gestation who were still alive when labor began. The subjects came from the Trent health region of the UK, between the in the time spans 1994-1999 and 2000-2005, in 16 different hospitals with over 55,000 births each year. Since the geographical region of Trent is appropriately representative of the UK as a whole, the authors believe that the data found in this region is comparable to the data that would be gathered from other parts of the country.

It was found that, while over half of the babies born at 23 weeks were admitted into intensive care, there was no improvement in survival for these babies in the 12 years of the study. Of these admitted babies, only 15% (12 of a total 65) of them survived the hospital stay. For the 150 babies born at 22 weeks, none were able to survive to discharge.

With this unfortunate lack of improvement in preterm infants born at 22 or 23 weeks, a significant improvement was found in the number of slightly more mature babies born at 24 or 25 weeks surviving until discharge. Of the babies in the category who were admitted to intensive care in the 2000-2005 period, 47% (236 of 497) survived to discharge. IN comparison, the earlier time period from 1994-1999 saw 36% (174 of 490) survival. According to the authors, these findings are not due to a change in resuscitation practices in obstetric or neonatal clinics, as they found that similar numbers of infants passed in the delivery room regardless of the time period. For example, of the babies born at 22 and 23 weeks, 58% (133 of 229) died in the delivery room in the earlier period, in comparison to 63% (126/200) in the later period.

The authors conclude that there has been a limit reached on the level of immaturity a premature baby can have and still survive.

Professor Neena Modi from Imperial College London contributed an accompanying editorial in which she points out that other factors often come into play when the survival of a preterm baby is at stake, including sex, exposure to antenatal steroids, whether it is a single or multiple birth, and birth weight. Thus, directives on care of extremely preterm babies should be completely based on gestational age, she says. However, the improved survival time of the more mature preterm babies indicates that we must make decisions based on the most up to date results possible.

Survival of extremely premature babies in a geographically defined population: prospective cohort study of 1994-9 compared with 2000-5
David J Field, Jon S Dorling, Bradley N Manktelow, Elizabeth S Draper
doi:10.1136/bmj.39555.670718.BE
BMJ Online First May 09, 2008
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Survival after extremely preterm birth
Neena Modi
doi: 10.1136/bmj.39559.518391.BE
BMJ Online First May 09, 2008
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Anna Sophia McKenney