We use the term ‘borderline of viability’ to describe extremely premature babies who are born at or before 25 weeks and six days (pregnancy usually lasts for 40 weeks).
In England, 1,600 out of 584,000 (0.28%) deliveries were at the borderline of viability in the year 2004-2005. This percentage has been increasing since the beginning of the 1980s, which may be due to a several factors, including the rise in fertility treatment.
Most extremely premature babies die, but the age at which they can survive has dropped by about one week for every decade in the past 40 years. A 1995 UK-wide study called EPICure showed that percentage of extremely premature babies born alive in 1995 who survived to leave hospital was:
- born between 22 to 23 weeks 1%
- born between 23 to 24 weeks 11%
- born between 24 to 25 weeks 26%
- born between 25 to 26 weeks 44%
(See Table 1 below). Survival before 22 weeks is very rare.
More recent data from other countries and specific areas in the UK indicate that survival rates have become higher since EPICure, and these may be more useful for providing advice to parents.
If an extremely premature baby survives to leave hospital, he or she may grow up with disabilities. Data from the EPICure study remains the best available for advising parents in the UK on likely outcomes. Of the babies born between 23 to 24 weeks who survived, about two thirds had moderate or severe disabilities. By 25 to 26 weeks, two thirds had no or mild disabilities (see Table 1).
When looking at these data, it is important to remember that a ‘mild’ disability need not affect everyday life, for example having a moderately low IQ score or needing to wear spectacles. Further, children who have disabilities due to prematurity represent an extremely small proportion of the total number of children with disabilities in the UK.
Other babies needing intensive care
Decisions about treatment do not just concern premature babies. Babies born at any gestational age can have brain injury, acquired during pregnancy or the birth itself, or, rarely, an abnormality of brain structure that remained undetected until after birth. A range of serious conditions affecting other parts of the body, such as the heart, lung, bowel and kidney may be found in the newborn child.