BPD is the biparietal diameter, which is the widest distance of the baby’s head, HC is the head circumference, which is the distance around the baby’s head, AC is the abdominal circumference and FL is the length of the baby’s femur. These are the indicators that women need to check regularly during their pregnancy to show in the most visual way if there are any abnormalities in the development of the fetus. They are also able to calculate the basic information about the height and weight of the fetus during each developmental period based on these parameters. These indices have their own normal range for each period of fetal development, and as long as the baby’s indices are within the normal range, most of them are not abnormal.