I think if it's a boy, you have good chance at that point, if it's a girl I think you may here, "its still too early". However depending on your size, baby growth, and position, I think you have a great chance at 15 1/2 weeks. With my first child it was obvious at 14wks.
Chloe - mom to Reece, (3) and Sophie, (7 months)
Hoping to TTC one more in late Spring of 2009! soon- 
