The reason why the fetus does not start after the due date may be related to the deviation of the calculation of the due date, the mother, the fetus or genetic factors. 1. Deviation in the calculation of the due date: irregular menstruation of pregnant women affects the accuracy of the calculation of the due date, and the actual due date will be later than the calculated due date, which makes it easy for the fetus to be delayed after the due date. 2. The mother: pregnant women estrogen and progesterone levels are out of balance, estrogen secretion is insufficient, progesterone secretion increases, it is easy to appear after the due date of the fetus delayed start. Pregnant women usually do not like to exercise, muscle contraction is not enough will also affect the frequency of uterine contractions, resulting in delayed start of the fetus. 3. Fetus: the fetus is too big to enter the pelvis normally, or the fetus enters the pelvis to the cervix to stimulate the effect of weak, abnormal fetal position, etc., will also lead to the phenomenon of delayed start of the fetus after the expected date of delivery. 4. Genetic factors: the presence of placental sulfate esterase deficiency in the family, the offspring will also be affected by the delay in the start of the fetus after the due date. Pregnant women after the due date of the fetus does not start late, but the fetus is normal, you can continue to wait, you can also go to the regular hospital in time to seek professional medical help.