In Oscar test (12 weeks and 6 days), doctor told me 70% baby boy, in 18 weeks, Dr. Peter Lo told me baby boy for sure, he scan a photo with the sex organ to me!!
At 11 weeks, my doctor told me that it's likely that my baby is a boy. At 15 weeks, she confirmed that it's a boy. I have heard that it's easier to confirm baby is a boy at an earlier stage because it's easier to notice baby boy's sex organ. Don't know if it's true though.