It is an age-old battle with small children that most parents will recognise: please, please, eat your vegetables. Some will read them books with titles such as The Boy Who Loved Broccoli . Others have been known to smother veg in tomato ketchup, or mix avocado and fruit with Greek yoghurt and call it icecream . Or resort to plain bribery. Now, a study suggests there may be a more effective approach – but mothers need to start early. Researchers have discovered that young children are less likely to react negatively to the smell of vegetables that they were repeatedly exposed to before birth. The implications could be huge. Prof Nadja Reissland of Durham University , the study’s lead author, said a consequence would be “that you have a healthier population”. Researchers gave some pregnant women kale powder capsules and others were given carrot powder capsules. They then examined and coded the facial reactions of their child to carrot or kale.…