Ay, 28 weeks ka na! Yes, pwde ka pa mag-4D ultrasound (CAS) at that stage, pero mas maganda ang resolution around 30-34 weeks kaya if you can wait a bit, mas clear talaga ang baby's features. I'd ask your OB muna kung okay siya sa timing dahil depends din sa amniotic fluid at baby's position, a few of us here tried going too early at ang result hindi na gaano clear, so mas sulit kung mag-hintay lang ng two more weeks or so. Your doctor will know best kung safe sá baby and kung worth it na talaga sa current stage, so check with her before you book!