Under 4D ultrasound, it is generally easy to distinguish the fetal penis from the umbilical cord under normal circumstances when performing prenatal fetal examination. When the fetus has developed to more than 24 weeks, the male child’s external genitalia have already developed and taken shape, and under the condition that the fetus is in a more appropriate position, the male child’s penis can be clearly displayed by 4D ultrasound. In terms of position, the penis is definitely between the boy’s two thighs; if the segment of the fetal umbilical cord also happens to be in this position, it is still very good to identify, because in comparison, the fetal cord is thick and large, while the child’s penis is short. In addition, you can use the color flow function test. The umbilical cord will show three red and blue blood flow signals, while the fetal penis has no blood flow signal, so it is good to identify.