PV testing is repeatedly done to know about dilation of cervix
,ripeness of cervix,effacament of cervix,position of your baby etc.
Although no lady likes it but it is proper on the part of your GYNEC to do it.
As far as vaginal infection
is concerned,there are no chances of it as it is done by using sterile gloves.
There is no harm to your baby by doing PV examination.