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. The exact cause of morning sickness is unknown. It may be caused by hormone changes or lower blood sugar during early pregnancy. Emotional stress, fatigue, traveling, or some foods can make the problem worse. Nausea in pregnancy is more common and can be worse with twins or triplets. Hormonal changes of pregnancy are thought to play a role.
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 cause of nausea and vomiting during pregnancy is believed to be rapidly rising blood levels of a hormone called HCG (human chorionic gonadotropin), which is released by the placenta.