Pwede na po ba mag pa ultrasound kapag 17 weeks & 3 days na?

for me mommy going to 20 weeks kna pa check up kc ung bilang mo bka iba dn pag nag pa ultrasound kna.. like me po sa ob ko sbi 20weeks na pero nag pa ultrasound aq kahapon 19weeks pa lng.. pero kita na gender its a boy hehehe..