Sexless baby??? Is it possible?

So my sister is pregnant with her second. Where I live, they do the anatomy scan and the tech will tell you right then and there the gender if you want. Now the thing is. They refused to tell my sister... and even the doctor has refused to tell her. I don’t think it’s cause they don’t know or couldn’t get a clear shot. They never asked her to come back and check gender and it’s been over two months since... she doesn’t really understand and no one else does. She asks the doctor but they just say they can’t tell her. I had my baby not too long ago, same hospital, same doctor and they told me everything. Same with my best friend. So now my dad thinks she’s having a baby with both sexes? Or no sex at all? Is this possible?