Common to the popular bikini streams is that they film themselves sitting in small inflatable pools filled with water.
The trend is called hot tub.
The increase is a loophole in the rules of the gaming streaming service.
Twitch regulations say that streamers must not be lightly dressed if they are not on the beach or bathing, something that is circumvented with the help of the diminutive plastic pools.
The bikini girls get lots of viewers and make money from donations and subscribers.
Stopped advertising
Twitch has received a lot of criticism for not trying to stop the trend - but now they have finally decided to go in and mark.
The other day, the site went in and stopped one of the world's biggest streamers Kaitlyn "Amouranth" Siragusa from having ads in her channel.
Siragusa has responded with outraged tweets where she believes that the restrictions have not been explained and risks hitting users who make a living on their streaming.
"Feels pressure from their viewers"
Effie Karabuda, game journalist at Swedish Radio, says that Twitch has long ducked the hot tub issue.
It has been speculated whether the site makes money on the girls or if they do not want to appear as moral police.
But as the criticism has grown, a careful attempt is now being made to get rid of the lightly dressed users.
- People have become so tired and complained so much about the hot tub trend that Twitch felt that: we have to do something, says Effie Karabuda.
The site has not yet communicated anything about why they chose to stop Kaitlyn "Amouranth" Siragusa's ads.
Now many users are wondering what will happen in the future.
- Twitch must comment on this publicly and say why they did this.
They need to tell what they think about this trend and maybe set up a new set of rules.
I think they feel pressure from their viewers.