Excessive vomiting during pregnancy

There are many different reasons why women may vomit more during pregnancy. The most common reasons are associated with pregnancy hormones oestrogen and progesterone. Oestrogen levels can increase a hundred fold during pregnancy. The change in homones can make some women more sensitive to smell and a smell overload can trigger nausea and vomiting. The hormone progesterone relaxes the stomach and intestines leading to excess stomach acid that needs to be removed by vomiting.
You vomit during pregnancy because your hormones are increasing and the chemicals are reacting. Depending on if you body can handle the chemical and hormonal changes, you may or may not vomit.
When you are pregnant your body does not know it has an actual physical being growing inside it, it just realizes that something odd is there that was not there before. The vomiting is usually the way our body throw out whatever is strange or making us sick. So, the vomiting in early stages of pregnancy is simply the body reacting to the foreign body inside it
The hormones. Towards the end of pregnancy it can be because the baby is pushing on the stomach