I was born with a heart murmur which was a type of fetal hear arryhythmia (irregular).
Since the day I was diagnosed I've had no complications, it just fixed itself. I still get the occasional irregular beat every now and then but I do not need medication, operations etc. and never have done.
I've lead a very active lifestyle - swimming, dancing, gymnastics, horse riding, netball, handball, the gym etc. - and it has never been an issue.
Nor does it stop me doing anything.
Don't worry hun, these things tend to pose little to no problems and most fix themselves, as mine has done to an almost complete extent.