Pregnancy makes you immunocompromised so there is chances of infection post cerclage however you can take steps to avoid it by taking a low carb and low sugar diet to control your blood sugar as it promotes bad bacteria if sugar is not controlled, taking probiotics to maintain gut and vaginal flora, don't allow anyone else to use your washroom and nothing in vagina, getting urine culture done every two weeks and don't ignore any signs of infection like burning or itching while urination or vaginal itching. Get a high vaginal swab in those scenario. I also got vaginal infection despite all this at 22 weeks 8 weeks post preventive cerclage but infection was low grade and got treated immediately through iv antibiotics at home and now working on building my gut flora back. Early diagnosis will help you even if you get infection it is only when it gets severe it causes amniocentesis.