Thanks to pregnancy hormones, late-night cravings for ice cream and pickles are common, but that doesn't mean you should always give in, says Dr. Hampton B. Richards, an obstetrician and gynecologist with Forest Park Medical Center in Dallas. “Evolution wants you to stock up on calories so you are ready if there is a famine, but we’ve moved past that,” he explains. Contrary to popular belief, you don’t need any extra calories in the first trimester and only 350 to 500 extra calories in the second and third trimesters. “This is the one time when you should NOT listen to your body,” Dr. Richards emphasizes. “Focus on healthy, whole foods just like outside of pregnancy and you won't go wrong. If you resist the temptation and keep your weight in a healthy range, you will have so much less pain at the end of the pregnancy," he says.