Patients are always advised by doctors to take off all jewelry or body piercing, prior to surgery as one of the major pre-surgery preparations.

These are the main reasons why doctors warn patients to strip off all jewelry before start of operation:

There is always the likelihood of jewelry falling into the body cavity that is being opened during operation, which can eventually cause other health problems, especially if it went unnoticed by the surgeons.
Wearing bracelet or ring that fits the size of our fingers and wrists can disrupt blood flow during operation.
Having jewelry on your body could affect over all hygiene and cause infections.

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Source: http://www.healthdiary365.com/2018/02/20/why-doctors-advises-patients-to-remove-jewelry-before-surgery/