BABIES born around 12 weeks early can now reasonably be expected to survive undamaged.

One out of every eight babies is born too soon each year. Most of the causes remain unknown and pre-term birth is the leading reason for neonatal death.

Babies born before 29 weeks are known as "extremely premature", but thanks to developments in research and technology, those born at around 27 weeks' gestation can have a greater than 90% survival rate. This compares to a survival rate of between 50% and 80% for babies born at 25 weeks.

A premature baby cannot typically be taken home in a couple of days. The newborn is taken to the neontatal intensive care unit where he or she will continue to grow.

There are 220 such units in the UK.

Dr Tom Turner, a recently retired consultant paediatrician at the Queen Mother's Hospital in Glasgow, said: "In the 21st century, being born at 27 weeks is not as risky as it was in 1970s, 80s or 90s. So many 27-week babies will survive. However, a lot depends upon the condition they were in when they were born and the conditions they were born into. It is an individual thing.

"The fact that the twins were shipped from Stornoway to Glasgow is not a major complication in itself. They would have been unable to stay in Stornoway because they almost certainly would need ventilation support.

"But as a general rule, at 27 weeks, at least you would be relatively optimistic."