Mild to moderate pulmonary stenosis is often nothing to worry about. I've had mild pulmonary stenosis my whole life and I'm 33 now (not a single issue) It has a benign course and doesn't increase in severity and wont affect life expectancy. They just need to make sure it isn't an ASD which often sounds similar. Again even an ASD (if treatment is needed) is equal to normal life expectancy :)
It's a possibility. However, often the pulmonary stenosis is a "fluke'. In my case, my mother AND grandmother had heart disease. My mom has had a mitral valve replacement with the mechanical valve and my grandmother has passed now from a heart attack. According to Doctors, what my mom and grandma has/had has absolutely no relation to the pulmonary stenosis that my daughter was born with. My daughter had a procedure at 1 week old, the balloon valvuloplasty. It was an awful thing to go through and I am sorry to anyone who has to experience it just after giving birth. But really, no time is a good time. She had moderate to severe pulmonary stenosis and we still do cardiac follow up. It sure has been a journey.