Mild Pulmonary Stenosis

I were born with PDA and that was corrected when i was 1 year old and later on the doctor found out that i have mild pulmonary stenosis with 20mmhg.That was when i was 11years old and now im 20 years old. My last echo showed pressure gradient with 30mmhg and EF:60%. I do have shortness of breath and gets tired easily nowadays. it not because im pregnant now. I use to have those problems before i got pregnant. Im in 32weeks of pregnancy now and the scanning shows my baby is just fine and nothing to worry. I just need to know is there any risk during the labor and is there any chances for the pressure gradient to increase? and why the pressure gradient has increased?