What does it mean if the fatty acids in a newborn are slightly high?

Depends. Usually needs to be re-tested, and/or have further testing to make sure there are no metabolism disorders.
Your doc should know. Most newborns are screened for dozens of genetic conditions immediately after birth. Some of theses conditions involve problems with fatty acid oxidation, the most common of which is mcad (medium chain acyl coa dehydrogenase deficiency). If the newborn screen shows signs of any one of these conditions, more specific tests must be done to confirm the diagnosis.