Ultrasound Accuracy: Determining Baby's Sex & What to Expect

Question
Hello There,
I was just wondering how accurate ultrasounds are in determing the sex of baby. I had one done at 18 weeks and I was told that it was a girl. The Tech showed us a pic of a bum (it just looked like a circle that was fuzzy) and said,  "I don't see a scrotum, so its a girl". We did not see any boy bits but we also did not see any girl bits. We saw nothing. Since then so many people have told me that they do get it wrong more than you would think? Also, I heard that the no testes=girl theory to also be wrong as testes may not even decsend until weeks 20-22. I am so confused and I just have met so many people that have been told the wrong gender because of the tech actually not seeing anything therefore assuming its a girl. I just want to know for sure. We have an older child to prepare and we don't want to get our hearts set on a particular gender if it may be wrong. It doesn't matter if its a boy or girl we just want to know for sure. Just wondering the real truth about ultrasounds..etc and is there any other way to tell...even through pics. We have 9 ultrasound pics...even of the whole body.
Any kind of solid info would be appreciated. Thanks...an axious mom.


Answer
You cannot guarantee gender based on sonography. HOwever, if you see a scrotum or a penis, it is definitely a boy. However, if you do not see the scrotum or penis, it may not be a boy because the genitalia may have been missed or hidden behind a leg, etc. (The testes are not seen on sonogram and do not descend until close to birth or thereafter).The only way you can be assured of gender is by amniocentesis where one can tell if there is an XY chromosome or an XX chromosome. If they did not see a boy, there is no way to be sure it is a girl.