The answer is portion control. But - since you are pregnant - really look at what you are eating. And ask your doctor what would be the caloric limit for you while you are pregnant. Tell him or her to be very specific with the range of calories.
When I was pregnant, I took a multivitamin for the pregnant woman, so I'm sure you must have had that recommendation. However, it's important to get enough calories also. Pregnancy is not the time to diet. You will be gaining weight, which tends to freak some women out anyway. But the person most important here is your unborn child. Balance, vitamins and minerals, some exercise and getting plenty of calories are important for your baby's health.