Help!!!

Tiajuana • I'm 36 and pregnant with my second child. I have a 15 year old also. I'm really excited! Can't wait to tell my family!!
So I went to my doctor today and I get blood work done next Monday. I'll find out the gender through blood work. How does that work? They are originally looking for any signs of birth defects. Anyone had this yet? Where is the blood drawn from?