Sex of the baby with a blood test?

I'm pregnant with my first and learning so many new things! I had never heard of this genetic blood testing they do in early pregnancy that can tell you the sex of the baby with a very high accuracy rate? They are doing the blood work at my 14 week appointment at the end of January, 6 weeks before a sono to confirm the sex. That's crazy to me! But exciting. Have you ladies heard more information about it or experienced it yourself? Tell me all you know or your experience. Excited learner over here :)