Aiyoh, I understand lah the worry, a few of us mums with smaller frames had the same concern masa pregnant dulu. It's true BMI rendah boleh slightly increase risks like prematurity, tapi the good news is many of us still delivered healthy babies, especially kalau we gained steady weight during pregnancy (even kecil badan, weight gain matters more than starting point). Since you mentioned baby dah lahir prem before, I'd really suggest sit down dengan your doctor or midwife this time to plan a personalized weight gain target, they can monitor more closely and give you peace of mind. Jangan stress too much lah, but definitely bring this up at your check-ups so they can track baby's growth on the scan and make sure everything's on track.