Referral to KKH

Hi mummies, has anyone been in this situation before: In the third trimester, experienced some unusual and worrying symptoms. Called obgyn at private hospital and asked to go to KKH for a check-up. Just wondering why go to KKH and not to the private hospital first, since I've been seeing their doctor there? Under what circumstances would obgyns refer mummies to KKH instead of their own hospital?