Standard value of fetal size at 13 weeks and its significance. During pregnancy, women often observe the size and development of the fetus through B-ultrasound, and the B-ultrasound examination performed around 13 weeks is a crucial examination time point. Because at this time the fetus has developed to a certain extent and its size has reached a certain standard value. This article will introduce the standard value of fetal size at 13 weeks and its significance. 1. The average size of the fetus is about 13 weeks, the size of the fetus is about 7.4 cm, and the weight is about 23 grams. This is the average, actually