A little nausea before menstruation is not clinically a sign of pregnancy. It is because the clinical symptoms of pregnancy, such as anorexia, nausea and salivation, do not appear until about six weeks after pregnancy, i.e. about 42 days after menopause. Nausea that occurs before pregnancy is often related to chronic gastritis or poor diet and is not necessarily a sign of pregnancy. If you are pregnant, you will not experience nausea at this early stage in the clinical process. It is only after the fertilized egg is laid, around 40 days after conception, that the estrogen level in the body increases to a level that can cause nausea and vomiting in pregnant women. Therefore, if nausea occurs before the menstrual period, severe cases can be examined in the hospital to rule out the possibility of chronic gastritis.