The last menstrual period was on March 11 and the presumed due date is December 18 of the same year.
The formula for calculating the expected date of labor is the month of the last menstrual period plus 9 or minus 3, and the date plus 7. The month of the last menstrual period is March, so the corresponding month of the expected date of labor is 3+9=12, i.e., December; the date of the last menstrual period is 11, so 11+7=18, i.e., the date of the expected date of labor is 18 days. Therefore, it is presumed that the expected date of delivery is December 18 of the same year.
This formula only applies to women who have regular menstrual cycles of 28 to 30 days. If a woman’s menstrual cycle is not regular, the expected date of delivery is based on the results of the ultrasound examination.
The expected date of delivery is only an approximation of when the fetus will be born, not the exact time. After pregnancy, women should go to the local maternal and child health care institutions to register for maternity and set up a maternity file, and follow the doctor’s instructions to standardize maternity checkups in order to detect abnormalities of the mother and fetus in a timely manner.