Nausea is included in the morning sickness of pregnancy.But it’s not necessary that every women face nausea or morning sickness.If neasea is present in pregnancy then that is a positive sign.Reason of Nausea & Vomitting during pregnancy—Vomiting or Nausea during pregnancy may be due to effect of a hormone produced by the placenta called HCG or human chorionic gonadotropin.Pregnant women begin producing HCG once fertilized egg attaches to the uterine lining.