During first trimester lang po mommy ang transvaginal ultrasound. Once you reached second and third trimester, pelvic ultrasound na sya. Yes, there's a big chance na makita na ang gender ni baby dahil 30 weeks ka na po. Usually 20 weeks onwards talaga ang pagpapa ultrasound for gender reveal pero depende pa rin sa position ni baby during ultrasound kung makikita agad. :)