The more prematurely a baby is born, the less EGF it has in its lungs and more risk it runs of developing chronic lung disease

Dr Sailesh Kotecha

Dr Sailesh Kotecha and his team at the University of Leicester believe the problem is caused by premature babies lacking a vital chemical - epidermal growth factor (EGF) - that stimulates the cells of the lung to mature.

These cells produce surfactant, a set of substances needed for the tissues of the lung to expand properly at birth to allow the baby to breathe.

Difficulties

Newborns that have spent less than 32 weeks in utero often experience breathing difficulties at the time or within hours of birth.

Doctors have two ways of dealing with the problem. They can either administer surfactant or try to restore and maintain normal levels of oxygen and carbon dioxide in the lungs and the blood.

For newborns whose respiratory difficulties are not too serious, it is enough to administer oxygen.

More severe cases, however, have to be connected to an artificial respirator.

About half the infants given mechanical ventilation do not recover normally and remain dependent on the oxygen supplied by the respirator.

These are the children that develop CLD.

Comparison

Dr Kotecha's team compared 16 babies who had developed a respiratory distress syndrome but had overcome it with 13 babies who had developed CLD, and six other babies who were under ventilation for other reasons.

They found that babies that developed CLD were born sooner and weighed less than babies that had overcome their respiratory distress syndrome.

The former were born after a gestation period of 27 weeks on average, compared with 31 weeks, and their average weight at birth was 820g, compared with 1415g.

The average gestation period of the six control babies was 33 weeks and their average weight 2,075g.

The researchers also found that EGF levels were lower in groups suffering from CLD or respiratory distress syndrome than in the control group.

Dr Kotecha said: "The more prematurely a baby is born, the less EGF it has in its lungs and more risk it runs of developing chronic lung disease."

Dr Warren Lenney, a consultant respiratory paediatrician from North Staffordshire Royal Infirmary, told BBC News Online: "Respiratory problems in premature infants are not only dangerous for the baby, but very expensive for the NHS - �40,000 in the first month of life alone.

"More research needs to be done but this is an interesting finding."

The research is published in the European Respiratory Journal.