Pregnant women who smoke may harm their babies' brain development if they turn to e-cigarettes to satisfy their nicotine craving, scientists have warned.

New research suggests that e-cigarette vapour may be as damaging as tobacco smoke to the nervous systems of the foetus or newborn infant.

Early findings, based on studies of mice, show that exposure to volatile chemicals from the devices disrupts the activity of thousands of genes in the developing frontal cortex, the brain region responsible for higher mental functions.