A speculum is a metal instrument consisting of two rounded blades on a hinge. It is placed inside the vaginal canal and the blades are then opened, allowing the doctor to see the mouth of the cervix (the opening of the uterus).
Because the speculum does not enter the cervical canal, most authorities rule that it does not make a woman niddah due to opening of the uterus.
A speculum examination does not usually cause any bleeding. If a small amount of blood is found on the speculum, it may be attributed to abrasion of the walls of the vagina – especially if the woman’s vaginal lining is sensitive or if the examination was performed without lubrication. (Gynecological examinations are often done with lubricating jelly; however, for a Pap smear only water is used, because the jelly can interfere with test results.) Such bleeding is non-uterine and does not make a woman niddah.
One does not need to ask the physician if blood is seen exiting the cervix. If, however, the physician does report blood exiting the cervix, the woman is typically considered niddah. A halachic authority should be consulted with any questions.