If you are diagnosed with this condition, your doctor or other health professional will give you detailed instructions about what diet to follow. Depending on how high your blood sugar levels are, and also on your weight even before the pregnancy, you may well be able to control it just by eating well and exercising.

The main things to avoid are saturated fats and sugary foods and drinks. Foods you should eat more of include lots of fresh fruit and vegetables (five portions a day is still the best advice) and other foods with a low glycaemic index (GI). A low GI means that the sugar from the food is released in to your bloodstream slowly, making it healthier for you. Low GI foods include porridge, wholewheat pasta, beans and sweetcorn and certain fruits. You should avoid foods like cornflakes, white bread and white rice which have a high GI. In fact this diet advice is generally good for anyone, not just those with diabetes.

You can get a fuller overview here, but it's also very important to talk about this with your doctor.