How does she know???

Shannon • I'm a mom to my beautiful 12 year old daughter Rylyn. And Jahna Nicoletta 9/29/16 my beautiful baby girl!!!!💖👶🙏💖
I had my 30 week ultrasound today, the doctor was in the room with the tech while she did it. When I was almost done she said to me your a little dehydrated, drink more water!!! How did she know that!!!! I am still puking and have awful diarreah!!! I am very curious to know how she can tell!!! 💖💖💖