I have had mvp my entire life but never need abx during labor. Just during dental work. If bacteria enter your bloodstream it can infect the valve of your heart and cause heart failure.
Current recommendations now are that abx are not even needed during dental work for those with mvp, the risk is small. I have mvp and tvp so I opt for them during dental work. Lots of bacteria enter the blood stream during dental work but not labor.
I would get the opinion of an OB. It just isnt needed.