Is they a big difference...

Just • 2 girls & baby girl no3 on her way 😘
I have a 3d gender scan booked for when I'm 15 wks exactly. The site say that you should be 16 wks but I'm away when I turn 16wks till 18 wks and don't wanna have to wait an extra two weeks lol. 
Anyway so my Q is will they be a big difference between babys genital development/distinguishment at 15w compared to 16w? 

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