sex of the baby

Last night around the dinner table Natalie: I will have a baby girl when I am older Rachel: you can not choose the sex of your baby. You might want a boy and might get a girl.... Mom: in fact you can tell sometimes. When the belly is big the doctor can place a camera on your belly and tell you the sex. Blank look Rachel: how is that possible? I show her how the camera works and give her a few samples Rachel: but mom, HOW can you tell if it is a boy or a girl? Mom: The boy has a penis (no mention of the extra genital part) big smile on her face