changing gender

So we found out we are having a girl the other day, or so the ultrasound technician says, and my boyfriend wasn't too excited. We were both wanting a boy, him more than I, I just want a healthy baby. Well today I hear him whisper "grow a penis" to my tummy (jokingly of course) so I said "it's a girl they don't just grow penises and testes after it's been formed as a vagina and ovaries." Then he said to me, dead serious in his face, that it can happen it's just really rare. Haha. He honestly thinks if he tells the baby to enough she might just magically grow a penis. but I'm pretty sure she's going to stay a girl. 😂