ANOTHER reason not to smoke during pregnancy: research from the US suggests it doubles the chance of a child developing a convergent squint later. The eight-year study, from the Johns Hopkins University, Baltimore, Maryland, also indicated that where mothers had stopped smoking before or during pregnancy, the risk of a child developing a squint was reduced to that of mothers who had never smoked.

The study, in the Archives of Ophthalmology, says a squint may be the result of a defect in the central nervous system. The crucial period may be the last three months of pregnancy, when the optic nerve system is developing.