In children, mumps is generally a mild illness, and complications are rare. When complications develop, they may include:

• Infection of the brain (encephalitis) and/or the membranes that cover it (meningitis).
• Inflammation of the testicles (orchitis) or ovaries (oophoritis). Orchitis may cause sterility in extremely rare cases; oophoritis does not appear to affect long-term fertility.
• Hearing loss.
• Inflammation of the pancreas (pancreatitis).
• Miscarriage, which may occur in a woman who has mumps during her first 3 months of pregnancy. There does not appear to be a link between mumps and birth defects.¹

Adults who are infected with mumps often have more severe symptoms and are more likely to develop complications than children. However, long-lasting problems from complications are rare.