It's been said that doctors have a basic idea of what's going in your body during pregnancy, they are still not completely sure what causes morning sickness.
Most people imagine that when you wake up in the morning, you’ll be nauseous, throw up, and then go on with your day. Well…that's partially true. Whoever decided to call it “morning sickness” was probably sleeping through the day because it doesn’t discriminate between the morning, afternoon, or evening.
During your baby’s development, you are likely to have bad reactions to foods that you may have liked or to just specific types of foods.
There’s no clear answer as to why nausea occurs during pregnancy, although it’s believed that it’s due to hormonal changes. Generally the nausea isn’t too overwhelming, and by mid-pregnancy, you should be relieved of it. However, if your nausea and vomiting are excessive, then talk to your doctor because it may be a sign of hyperemesis gravidarum, a rare complication that results in a poor intake of fluids and food.
Although you can’t really prevent morning sickness, studies show that women who took multivitamins before conception are less likely to get nauseous. Each woman is different, and we'll never be able to pinpoint one factor or even several causes of morning sickness.