From the CDC Guideline for Prevention of Surgical SiteInfection, 1999:

The wearing of surgical masks during operations to prevent potential microbial contamination of incisions is a longstanding surgical tradition. However, some studies have raised questions about the efficacy and cost-benefit of surgical masks in reducing SSI risk. Nevertheless, wearing a mask can be beneficial since it protects the wearer’s nose and mouth from inadvertent exposures (i.e., splashes) to blood and other body fluids.

There is a Guideline from 2017, but it does not mention surgical masks at all, which means this 1999 document is the most up-to-date opinion of CDC on this matter.