Common knowledge about pregnancy: Why is the expected date of delivery calculated at 40 weeks? Pregnancy is an important stage in a woman\’s life because during this period, both the mother\’s body and the fetus require special attention and care. Among them, the calculation of the due date is one of the most important aspects of pregnancy. So, why is the expected date of delivery calculated at 40 weeks? This article will elaborate on the calculation of gestational age, female physiology, fetal growth and medical practice. first part: