21 weeks is usually accurate na for gender reveal, lalo na kung malinaw ang ultrasound at ang baby's position ay cooperative! A few of us tried scheduling our gender reveal around 20-22 weeks kasi mas visible na talaga ang genitals, pero I've heard ng cases din na kailangan ulit mag-check if inconclusive ang first viewing. Best talaga na confirm with your OB kung confident na sila sa reading bago mag-invest sa big reveal, para walang disappointed surprises after!