Leading article: False friends

As every pregnant woman knows, joy at the discovery that she is soon to become a mother turns rapidly to anxiety about how to protect her unborn baby. Threats seem to appear at every turn, from the food on her plate, to the pollutants in the air she breathes, and the wine in her glass.

Medical drugs have long been suspect since the disaster of thalidomide almost 50 years ago. But now researchers have discovered that even the humble, and ubiquitous, antibiotic may pose a risk. In the largest study of premature labour in the world, researchers from the University of Leicester have found that in women whose waters had not yet broken, there was an increase in the incidence of cerebral palsy and other problems such as poor eyesight, among those given antibiotics.

The message is complex, but it is critical that it is understood. Antibiotics are vital to treat infection in pregnancy, which can kill mothers and babies. But they must not be used on a "just in case" basis, where there is no sign – or risk – of infection, as they too often are.