Nausea is included in the morning sickness of pregnancy. But it’s not necessary that every woman face nausea or morning sickness. If nausea is present in pregnancy then that is a positive sign.

Reason for Nausea & Vomiting during pregnancy—Vomiting or Nausea during pregnancy may be due to the 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.