The move comes after Newsroom revealed at least four women had come forward and accused Ross of harassment.
"We are getting independent advice to make sure we have got the best systems and process so women do feel safe."
Bridges did not think there is a cultural issue within the National Party – "but the reality is several women have been affected by what has happened".
He said he wanted to make sure National can do the best for its future.
How the review would look is an "open question at this stage".
The results of that review probably won't be made public, he said.
The review, he said, was to ensure the culture would be the best it could be.
He admitted National had fallen short in some areas of the Ross saga but didn't think there was anything they could have done differently.
Ross was taken to the mental health unit in Middlemore Hospital on Sunday following an incident on Saturday that a friend, who did not want to be named, has described as a serious situation and far from a "cry for help".
Bridges said he didn't know about this until after it had happened, but would not comment on specifics as he is not familiar with the first-hand details.
He said this is now a matter for the right authorities to deal with.
He said National had made the "right call" for the right reasons" and he had done "the right thing at every step of this".
"I have acted entirely consistent with the specialist medical advice at every step of this."
Last week, Deputy Leader Paula Bennett told the Herald issues raised with Ross had nothing to do with harassment but were about inappropriate behaviour from Ross as a "married Member of Parliament".
Bridges said Bennett has acknowledged that "she didn't get it all perfect".
He had spoken to her about the comments.
Bridges said because Ross was unwell, it was "incredibly unlikely that we will use the waka-jumping law".
He said National would be unlikely to use the bill in any other circumstances.
His leadership would not come up in caucus today, he said.
Meanwhile, National MPs are standing behind Bridges and have offered support to Ross.
Rodney MP Mark Mitchell said the caucus' support for Bridges was "unwavering" and that won't change.
He said he had met with Ross three weeks ago to ensure he was getting the proper support he needed.
"I didn't offer him anything other than support and to get well and to make sure he was focused on his own health."
List MP Brett Hudson said the events of last week showed the party's leadership and its caucus handled the situation "very well, given the information we had".
Paul Goldsmith said he was worried about Ross. He does not know the details, but said he is "sure he is under very good care".
On how the Ross saga was handled, Goldsmith said the caucus handled the "very, very difficult situation the best way that we could".
Melisa Lee said everything the party and its leadership had done, in relation to Ross, had been done correctly.
Just moments before Bridges announced the review, National MP Nicola Willis said she didn't think an inquiry into the culture of the National Party was needed.
"The culture in the National Party for me has always been one that has been supportive and positive and I have really appreciated that."
