BPD means the diameter of is. The parameter size between the two sides trying to disturb the embryo specifies and from Week Thirteen of the pregnancy to the next to be measured. Much, it from 2. the 4 cm in Week Thirteen to 9. the 5 cm at the end of the pregnancy changed. Of course, the fetus different size heads have different and determine the time of delivery on the basis of this parameter, accurate, and very reliable, will not be.