Pregnancy tips Nausea and Vomiting in Pregnancy Caused By A Number of Factors

I've always wondered why some women (like me) get terribly sick with pregnancy and other women sail through feeling great the whole time. Here is an article that explains some possible causes of nausea and vomiting in pregnancy (scroll down to see article):

Nausea & Vomiting During Pregnancy
by D. Ashley Hill, MD, OBGYN.net

From the article:

"While the exact cause of nausea and vomiting of pregnancy is not understood, there may be a link between relaxation of the muscle fibers within the walls of the stomach muscle. Other researchers have noticed changes in bacteria counts in women who have morning sickness. They have found higher than normal levels of a bacteria called helicobacter pylori, which also seems to cause ulcers. Research is ongoing to see if certain antibiotics will treat hyperemesis. Others have found a link to the chemical serotonin, and to elevated levels of the pregnancy hormone HCG. For example, patients with twins or triplets have higher levels of HCG, and are more likely to have vomiting during pregnancy. There is also a higher chance of having severe nausea and vomiting, called "hyperemesis gravidarum," in patients with uncontrolled thyroid problems (hyperthyroidism). "