Morning sickness, also calle nausea, vomiting of pregnancy (emesis gravidarum or NVP), or pregnancy sickness, affects between 50 and 95 percent of all pregnant women as well as some women who use hormonal contraception or hormone replacement therapy. The nausea can be mild or induce actual vomiting. In extreme cases, known as hyperemesis gravidarum, hospitalization may be required to treat the resulting dehydration, which occurs in about 1% of pregnancies.