Hey mama! You're right, usually around 26-28 weeks (around 6-7 months) is the sweet spot for 4D kasi the baby's features are clearer na pero not too cramped pa sa tummy like ngayon at 33 weeks, mas mahirap makita ng clear image pag malapit na mag-deliver dahil mababa na sila and may less amniotic fluid. But honestly, a few of us tried 4D at different weeks and nakakuha pa rin ng decent shots even later, so depende talaga sa position ng baby at ang skill ng technician, pero kung gusto mo talaga ng best quality images, you might've caught the perfect window na talaga a few weeks back.