What causes morning sickness in pregnancy?
As many pregnant women know, the bouts of nausea and vomiting that are commonly called "morning sickness" can happen any time of day. An estimated 60 to 80 percent of women experience this symptom of early pregnancy, which may be caused by hormonal changes and can be aggravated by stress or fatigue. For most women, the nausea and vomiting fade by the 17th week of pregnancy. In rare cases, a pregnant woman will experience morning sickness well past this point. Even more rare is hyperemesis gravidarum, a very severe form of morning sickness that prevents a pregnant woman from keeping in the fluids or nutrition she needs. This condition requires medical treatment.