Ultrasound Worries

My 20 week ultrasound is exactly a week from today.  Now, I have had the worries in the past that: a) my baby would be dead, b) something is wrong with my baby, and c) that I will be able to tell the sex of the baby (I want to have a surprise).  But, I called my mom last night, she's coming into town for the ultrasound, and she asked what would happen if I saw the baby's genital area and knew what it was.  I told her that I was planning on looking away.  To this she said, "I'm not going to look away."  Really Mom?  Thanks a lot!!  Now, not only do I have to worry about myself and Caleb seeing, but I have to worry about you seeing, too.  She says she could keep a secret, but no, not going to happen if I can help it because this is her first grandchild and I just KNOW that she would slip up at some point and say something or buy me gender specific clothing... thus ruining my surprise.  Can you tell I'm super worried about this and kind of mad at my mom for saying this?!?!  But, I'm hoping everything goes well, and I'm actually hoping that the baby is cross his or her legs!  And, PLEASE let me have the ultrasound tech who has done every ultrasound on me since the day that I went in for my second opinion on my miscarriage.  That is all!!  :)