✔ 最佳答案
This is not only the difficulty of position (baby is moving in mother belly), but it is also because of the posture of the baby (umbilical cord overlapping with penis), experience of the doctor (image recognization is not a easy ,atter, so there is a specialized doctor to do the ultrasound and radiographic imaging report called "Radiologist"), the ultra-sound machine (2D or using latest and advanced 4D ultrasound machine with Dropper imaging faciliate).
Some clinic or doctors are using the 2D ultrasound machine for BB, therefore it is not easy to interpret the image. Also latest develop of ultrasound for BB is 4D imaging with Dropper imaging.
4D can show the 3D image of the baby in a recording time frame, so the image will be a real-time 3D image of the BB, so it is more accurate (about 90% to 95%). The Dropper imaging can be used to differentiatize the umbilical cord and the penis, so it will be more accurate if they are using with 4D imaging.
Finally, if the baby penis is small that will not easy be recognized, then the doctor will most probably say that is a girl. If the penis can be recognized by 4D ultrasound with Dropper imaging, the doctor will say that the baby is a boy with some excuse for their reputation protection too.