Neuroscience: The brain, interrupted

Illustration: Paddy Mills

Fabienne never found out why she went into labour three months too early. But on a quiet afternoon in June 2007, she was hit by accelerating contractions and was rushed to the nearest hospital in rural Switzerland, near Lausanne. When her son, Hugo, was born at 26 weeks of gestation rather than the typical 40, he weighed just 950 grams and was immediately placed in intensive care. Three days later, doctors told Fabienne that ultrasound pictures of Hugo's brain indicated that he had had a severe haemorrhage from his immature blood vessels. I just exploded into tears, she says.

Both she and her husband understood that the prognosis for Hugo was grim: he had a very high risk of cerebral palsy, a neurological condition that can lead to a life of severe disability. The couple agreed that they did not want to subject their child to that. We immediately told the doctors that we did not want fierce medical intervention to keep him alive and saw the relief on the doctors' faces, recalls Fabienne, who requested that her surname not be used. That night was the most tortured of her life.

The next day, however, before any change had been made to Hugo's treatment, his doctors proposed a new option to confirm the diagnosis: a brain scan using magnetic resonance imaging (MRI). This technique, which had been newly adapted for premature babies, would allow the doctors to predict the risk of cerebral palsy more accurately than with ultrasound alone, which has a high false-positive rate. Hugo's MRI scan showed that the damage caused by the brain haemorrhage was limited, and his risk of severe cerebral palsy was likely to be relatively low. So just 24 hours after their decision to let his life end, Hugo's parents did an about-turn. They agreed that the doctors should try to save him.

Thanks to medical advances since the 1970s, premature infants those born before 37 weeks of gestation are increasingly able to survive. Some hospitals now try to save babies born as early as 22 weeks. But those developments are forcing doctors and parents to grapple with difficult decisions, because the chances of severe disability increase with the extent of prematurity. Cerebral palsy, for example, affects 12% of babies born at term, 9% of those born earlier than 32 weeks and 18% of those born at 26 weeks.

That is just half the story. Neuroscientists are developing an increasingly sophisticated picture of premature infants' brains that could help to inform medical decisions and treatments. From some long-term studies, they are learning that premature children face a higher risk than was previously thought of developing cognitive or behavioural problems according to some studies, as many as half of them will.

Researchers are starting to ask why this should be, whether it could be avoided and what is the best way to provide educational support for the affected children. We need to gather a lot more data to understand what the best strategies are, says Petra Hppi, a neonatologist and developmental paediatrician at the University of Geneva in Switzerland, who is following the brain development of children who were born prematurely.

Prematurity also called pre-term birth is extremely common. According to World Health Organization statistics from 2012, more than one in 10 babies around 15 million in total are born prematurely each year. The great majority are born between 32 and 37 weeks of gestation, but 1.6 million are born between 28 and 32 weeks and 780,000 are born 'extremely pre-term', before 28 weeks (see 'Born too soon').

Source: H. Blencowe et al. Lancet 379, 21622172 (2012)

In low-income countries, more than 90% of extremely pre-term babies born alive soon die, which helps to explain why prematurity is now the second biggest cause of death in children under five, after pneumonia. But in richer countries, with sophisticated neonatal intensive-care facilities, more than 90% of these extremely pre-term babies survive, and doctors are continuing to push the age of survival even earlier in development. Doctors in the United States are debating a controversial recommendation to lower the gestational age at which a baby should be considered potentially viable from 24 weeks to 23 weeks. In Japan, babies born at 22 weeks have been considered viable since 1991.

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Neuroscience: The brain, interrupted