GBS Vaginal swab test

Read few posts here about GBS test for bacterial infection. Most comments suggested to do the test compulsorily. I'm week 26 now. But doc never mentioned anything about it. During what stage/week is it usually done? I have my next appointment in less than 2 weeks. Should I ask doc myself or if it is done in later stage of pregnancy then I wait for doc to suggest? Please advise. Thanks 😊 #1stimemom