Sex slavery in in USA, UK and Australia

I understand this stuff happens all the time in most parts of the world but I just watched Room. It's about this 24 year old who was held captive as a sex slave for 7 years and fell pregnant to her capturer and it left me in tears. I know we occasionally hear about horror stories like this on the news but I was just wondering how often this kind of stuff happens in developed countries; more specifically USA, UK and Australia.