Detailed explanation of fetal size and development in the third trimester. In the third trimester, the fetus has basically formed and begun to take on its true appearance. The fetus is about 5 centimeters from head to toe and weighs 12 grams. The following is a detailed explanation from four aspects. Appearance characteristics: The appearance of fetuses in the third trimester of pregnancy has begun to show obvious differences. At this time, the head is still very large, accounting for more than half of the entire body length, but the neck has formed and the boundary between the head and neck is more obvious. On the head, facial features have begun to appear,