Have to wait till 21 weeks

I'm 16 weeks 3 days today. My doctor called last week and I go July 6th for my anatomy scan for baby g#3. Ill be 21 weeks 2 days by then. I had my last son 8 years ago so I can't remember exactly when we found out the sex but I don't remember waiting this long. Did anyone else have to wait till 21 weeks?