Seems like the norm for providers is not to give one till at least 8-12 weeks. My OB gave me one right off the bat when I went in for initial blood test confirmation, and I've gotten one every week since then (this week will be my 3rd). I was diagnosed with a odd shape uterus so OB wants to closely monitor me.

Pro is that I get to see how this pregnancy is progressing, but con is that I'm at the doctor every week and it's hard to see anything so early! I also read some articles about potential negative effects of too many ultrasounds...