To the expected date of birth is not yet born may be the cause of long menstrual cycle, fetal position, hormone ratio imbalance and other reasons. 1. Long menstrual cycle: women usually have a long menstrual cycle, the menstrual cycle more than 35 days, the fertilization of the egg will be delayed than, may not be born after the due date, at this time to re-verify the gestational week. 2. Fetal malposition: pregnant women with cephalic disc disproportion, because the fetus is too large delayed entry into the pelvis, the fetal prelude can not press the cervix to promote cervical ripening, which can lead to delayed labor, to the expected date of birth is not born. 3. Hormone imbalance: the estrogen level and progesterone level in a woman’s body are imbalanced, with a low estrogen level and a high progesterone level, which may lead to a delayed or overdue pregnancy, and a failure to give birth by the due date. There are more reasons for not giving birth by the due date, and it is normal to deliver within two weeks of delaying or advancing the due date, so it is recommended that you seek medical attention for a maternity checkup on time.