Giving birth naturally increases the risk of minor brain haemorrhages in newborn babies, according to a study. Brain scans of babies aged between one and five weeks showed small ruptures in blood vessels in or around the brain are common, affecting one in four children born naturally.
Babies delivered by caesarean section showed no signs of even minor bleeding.
In most cases, the haemorrhages are harmless and heal naturally, but larger ruptures can affect brain development, leading to seizures, or problems with learning or coordination.
Doctors at the University of North Carolina, Chapel Hill, used magnetic resonance imaging (MRI) to scan 88 healthy newborns. Of the 65 delivered naturally, 17 had intracranial haemorrhages and seven had ruptures in at least two separate regions.
John Gilmore, a professor of psychiatry and lead scientist on the study, said the bleeding was not caused by the size of the baby or the baby's head, the duration of labour, or the use of vacuum or forceps to assist delivery. "The bleeds are probably caused by pressure on the skull during delivery," he said.
The scientists noticed the high rate of haemorrhages while conducting scans to assess brain development in children perceived to be at high risk of mental disorders. "What we've shown is that if you get these bleeds, you don't have to think something has gone wrong with the delivery, because these are common," said Prof Gilmore, whose study is published in Radiology.
The team will conduct further scans when the babies are one and two years old. This may help doctors assess future cases of "shaken baby syndrome", where injuries to a baby are contested. In some cases, parents or guardians claim brain injuries have been inflicted naturally at birth. The scans may reveal whether small haemorrhages at birth grow to become more threatening, or gradually heal with time.