Hi mama! Honestly, both are safe at 20 weeks kaya okay lang mag-decide based sa budget and what you really want, marami sa circle ko ang nag-2D lang para sa medical check and medyo pricey talaga ang 4D, pero some of us splurged for the cute baby photos haha, it really depends sa priorities mo! For peace of mind though, best to ask your OB kung anong mas kailangan mo right now, whether it's CAS first or pwede na agad ang 4D. Either way, maganda yan both para makita ang baby mo!