Morning sickness is nausea or vomiting that usually occurs during the first trimester of pregnancy.
Despite its name, you may feel nauseated or vomit at any time of day. More than half of pregnant women have morning sickness during the first trimester. It usually goes away by the second trimester, when the level of pregnancy hormones in your body falls. When morning sickness is severe, it is called hyperemesis gravidarum . It is not understood why some women develop morning sickness, but certain factors such as hormones are involved.