March 20 last menstruation due date is probably December 27, not all pregnant women to the due date will deliver the fetus, delayed or 2 weeks early most of the normal. After pregnancy, according to the time of the last menstrual period, you can deduce the expected date of labor, the month is greater than 3 minus 3, less than 3 plus 9, the date plus 7, out of the expected date of labor time. If the first day of the last menstrual period is March 20th, then the expected date of delivery is about December 27th. Women are also able to approximate the number of days of pregnancy based on the time of their last menstrual period. The date from the first day of the last menstrual period to the present is the time of pregnancy. The expected date of delivery is exactly 40 weeks, 280 days, that is, 10 months of pregnancy, not all the fetus is just to the expected date of delivery out, in the expected date of delivery delayed or 2 weeks ahead of the time of delivery are normal. Clinical pregnancy should regularly go to the hospital to do a good pregnancy checkups, found that there is an abnormality in a timely manner.