>Little Jennifer Jane Brown was too small and fragile to survive outside the womb

Jennifer Jane Brown weighed just 2lbs 4oz when she was delivered by Caesarean at 33 weeks on 28 December. She was born early because a scan revealed concerns about her heartbeat and growth - the average weight of a baby at 33 weeks gestation is approximately 4lbs 5oz.

If the placenta fails or malfunctions, a baby can stop growing, and be deprived of nutrients or oxygen. Jennifer Jane Brown would have been at risk if the pregnancy continued.

She was transferred immediately to a special care baby unit, where her heart function, breathing, blood pressure and body temperature would have been closely monitored. Oxygen, ventilators and tube feeding would also be available.

Tiny babies are ultra sensitive, and cannot respond to more than one type of stimulus at a time - for example touch and sound - so they are handled very gently, and the special care baby unit is kept quiet with low lighting.

The relative risks
The decision to deliver a baby before 40 weeks is not taken lightly. The risks to life within and outside the womb have to be quantified. For instance, babies weighing less than 3lbs 5oz at birth are more at risk from the complications of immaturity.

The length of time a baby spends in the womb directly relates to its chances of survival. There is evidence that, during the first days outside the womb, a premature baby puts normal maturing on hold while she uses all her energy to survive. These babies do mature in the normal way, but it simply happens later.

Immature lungs pose the most serious danger, especially the threat of respiratory distress syndrome, in which the air sacs cannot function adequately to exchange oxygen and carbon dioxide and small babies may require oxygen and even a ventilator until they become stronger.

A delay of even 48 hours can make a significant difference. Steroids administered to the mother can speed up development of the lung lining. This helps most infants between the ages of 26 and 35 weeks and poses no serious risks to either the mother or the baby.

Initial reports, which gave cause for hope, indicated that Jennifer Jane was breathing by herself and taking a little food. Breast milk can help prevent infection in premature babies, and can be supplied from a milk bank, or the mother can express colostrum - the early milk that contains high levels of protective antibodies and protein.

Early birth complications
'Every day of development during pregnancy is precious to the health of an unborn baby,' said Dr Jennifer Howse, president of the March of Dimes, a voluntary organisation that funded a study of several million American and Canadian babies born prematurely. 'The finding that prematurity is associated with higher risk of death gives even greater urgency to our efforts to find ways to prevent pre-term birth from occurring.'

Advances in neonatal intensive care technology mean that a 33-week baby stands a very good chance of survival. But Jennifer's low birth weight added to her fragility. Her vital systems were not sufficiently developed, as she was the size and weight of a baby at 28 weeks gestation.

Risks to the brain
Although babies born as young as 23 weeks have survived, there is a higher risk of infection, lung damage, cerebral haemorrhage and water on the brain, and later developmental delays and handicap.

The large numbers of tiny capillaries required to supply the brain with blood can be very fragile in a premature infant. Cerebral haemorrhage is a risk, and premature babies are scanned by ultrasound within days of birth to check for bleeding, as it can be difficult to diagnose.

If the amount of blood leaking is small, then the brain eventually reabsorbs it and the baby recovers. No treatment, apart from sedation to keep the baby calm, is currently available. However, there is evidence that Jennifer suffered a serious cerebral haemorrhage within days of birth and, in spite of the very best medical care, was too fragile to survive in the outside world. After just ten days of life, she died quietly in her parents' arms.

Most of us are allowed to mourn in private - Gordon and Sarah Brown had the added burden of having to bear their grief in the public eye.

Research is continuing into the risks of low birth weight and prematurity. There is some evidence that magnesium taken during pregnancy can help prevent cerebral haemorrhage.