The last menstrual period is April 13th and the expected date of delivery is January 20th of the following year, but there may be some variations due to individual circumstances. According to a woman’s normal menstrual cycle of 28 days, the fetus develops in the uterus until 40 weeks of delivery, the expected date of delivery is calculated as the month of the last menstrual period minus 3 or plus 9, and the date plus 7. The last menstrual period is April 13, the month minus 3, which is January of the following year, and the date plus 7, which is the 20th, so the expected date of delivery is January 20th of the following year. Due to many factors affecting the ovulation period of women, there may be ovulation in advance or after the wrong time, the fertilization of the egg will also appear on the time difference; coupled with the individual differences in pregnant women, labor contractions will be launched on the time will also be different. Therefore, as long as the development of the fetus is good, amniotic fluid, placenta and other tissues are not abnormal, fetal heart, fetal movement and other conditions are normal, relative to the expected date of delivery two weeks ahead of or behind the normal situation. Pregnant women must closely observe their own and their fetus’s condition and have regular pregnancy checkups to ensure the health of the pregnant woman and her baby.