Apple has determined that, in a limited number of 13-inch MacBook Pro (non Touch Bar) units, a component may fail causing the built-in battery to expand. This is not a safety issue and Apple will replace eligible batteries, free of charge. Affected units were manufactured between October 2016 and October 2017 and eligibility is determined by the product serial number.
Note: If your 13-inch MacBook Pro has any damage which impairs the replacement of the battery, that issue will need to be resolved prior to the battery replacement. In some cases, there may be a cost associated with the repair.