Brown discharge can be a sign of pregnancy if you're trying to get pregnant.
Brown discharge is also known as spotting and usually occurs before a period and the brown discharge is caused by implantation bleeding that happens when the fertilized egg burrows in the uterus lining.
The discharge can also sometimes be pink instead of brown and not every pregnant woman experiences spotting or discharge but some do experience it.
If you're not trying to get pregnant then brown discharge is also normal but yes brown discharge is a common sign of early pregnancy.