“What happens if you don't eat enough while pregnant?”

So, first of all, depending on your pre-pregnancy weight, it may or may not be important. Certainly, if you start out at 90 lbs, then you should make sure to gain 25-35 lbs during the pregnancy. If you are heavier, then you do not need to gain that much weight, and if you are overweight, then you only need to gain about 10 lbs, and almost all of that is in the 3rd trimester. So, instead of stressing by how much you eat, you should use your weight when you see the doctor and see how much weight you have gained and how far along you are. Don't forget, most people gain half their weight up to 28 weeks and half afterwards. 
I hope this helps.  

Joseph A. Adashek, MD FACOG

Hi, eating is essential to provide the nutrients necessary for the growth and development of your fetus. If you are not eating well you should determine why. Taking prenatal vitamins with extra folic acid may be helpful. However, it is still crucial to eat during your pregnancy for both yours and your fetus's well-being.