First week of pregnancy syptoms?

A regular period: Pregnancies are counted from the first day of the last menstrual period before conception. So, the first week of pregnancy is just a normal menstrual period. The second week of pregnancy is the normal week after a period, before ovulation. Ovulation usually starts at the beginning of the third week of pregnancy. Implantation is in the fourth week. Symptoms start during the fourth and fifth weeks.