Ah yes, puwede naman mag-pineapple juice habang buntis, pero not in excess lang, marami kaming kaibigan na nag-enjoy pa rin ng juice throughout pregnancy! Ang concern lang talaga ay ang acidity nito, kaya better to drink in moderation at dilute it with water para mas safe, at sip through a straw to protect your teeth. Since you're 20 weeks na, definitely good time to ask your OB about what fruits and juices are best for your specific pregnancy, they'll give you personalized advice based on how you're doing.