There is no reaction on the first day of pregnancy because the fertilized egg has just formed on the first day of pregnancy and is still in the fallopian tube and not free into the uterine cavity, which does not affect the hormonal levels of the pregnant woman and does not cause any reaction to her body yet. The majority of women do not feel anything during the first month of pregnancy, and there is no way to detect pregnancy when the fertilized egg has just formed, whether it is a urine pregnancy test or a blood test for chorionic gonadotropin. Normally, early pregnancy reactions, such as vomiting, loss of appetite and poor mental health, will not appear until about thirty days into pregnancy.