Pregnancy is usually counted from the first day of the last menstrual period.
Clinically, for women with regular menstrual cycles, the first day of the last menstrual period is usually used to calculate the number of days of pregnancy, and the entire pregnancy cycle is 280 days, totaling 40 weeks. This method of calculation makes it easier to calculate the week of pregnancy and the expected date of delivery.
For women with irregular menstrual cycles, it is recommended to go to the hospital for an ultrasound examination to calculate the number of days of pregnancy based on the size of the gestational sac.
Clinically, the first day of the last menstrual period is used to calculate the number of days of pregnancy. For pregnant women who are unsure of the time of pregnancy, it is recommended to go to the hospital for checkups and carry out pregnancy care under the guidance of the doctor, avoiding self-estimation of the number of days of pregnancy, which may lead to adverse consequences.