Morning sickness is nausea that occurs during pregnancy. Morning sickness affects a large proportion of pregnant women. It is most common during the first trimester. Some women have nausea and vomiting through their entire pregnancy. Hormonal changes of pregnancy are thought to play a role. Changes include rapidly increasing oestrogen levels, an enhanced sense of smell, excess stomach acids, and increased fatigue. Some researchers think that stress and emotions also play a part in morning sickness.
Rarely, severe or persistent nausea or vomiting may be caused by a medical condition unrelated to pregnancy such as thyroid or liver disease. Treatment isn't necessary for most cases of morning sickness. If your morning sickness symptoms persist, however, your pregnancy care provider may prescribe vitamin B-6 supplements, antihistamines and possibly anti-nausea medications.The most severe form of morning sickness is known as hyperemesis gravidarum (HG) affecting less than 2% of women. This is when a woman has constant and severe nausea and vomiting resulting in weight loss and dehydration.