I had a follow up US this morning. The left ventricle has not gotten any bigger (still a 10) and is the highest end of normal. The right ventricle remains perfectly normal (measuring at 6mm).
The doc was amazing. She told us this is "honestly no big deal at ths point" and that there is a 90-95% chance that there will be absolutely nothing wrong. She also patiently answered all of our questions and explained what changing meaurements would mean. I have to have USs every 4 weeks to continue monitoring the measurements.
I am so happy and relieved at ths point. I feel like I am able to fully enjoy the pregnancy now. Also, our little girl spent most of the US waving to us - so cute!
Thank you to those of you who have answered my questions, offered a kind word, and just generally been awesome. I appreciate it more than I can express.