The guy above who said the baby kicks your intestines and it goes to your throat is a moron. When your pregnant your more prone to be sick and often times vomit. Your appetite usually changes when your pregnant. If you haven't eaten recently and you happen to feel the urge to throw up, chances are your going to throw up bile. You will throw up bile if there's nothing in your stomach to throw up.
You're probably referring to bile. If you throw up bile, it means that you have absolutely nothing in your stomach, not even water. Bile can erode the lining of your esophagus, so make sure, you always are at least hydrated (so you throw up water). Also, you can eat a plain cracker right before getting out of bed if you throw up in the morning.
Because when your pregnant the baby kicks on your stomach and it makes your intestentines goup tot your thoat.