Sis, usually around 18-20 weeks na talaga makikita ng doctor ang gender ng baby sa ultrasound, though some clinics pwede na mag-detect ng slightly earlier if baby cooperates haha! Depende rin sa clarity ng machine at kung maayos ang position ng baby, kaya minsan kailangan ulitin if di clear ang view. Best talk to your OB about the best timing para sa inyo so they can schedule it when baby's most likely to show off, it's one of the most exciting appointments, enjoy it!