Mine took round about 20 mins
They check for any abnormalities and if babies growing ok and then let you go. I don't know if the woman i had was intending to tell me the sex so i had to ask her. So just mention it to yours when you go in to be on safe side

and make sure you have a full bladder lol as the woman wasn't happy with me for going not long before and was going to get me to come back in twenty mins later but baby ended up moving on her own

xx