Hey mama, congrats on 34 weeks! So BPS (biophysical profile) checks baby's movements, breathing, and amniotic fluid level, it's more about how baby's doing in real-time, while fetal biometry is basically measuring baby's head, belly, and thigh bone to track growth and make sure development is on track. Your OB probably wants biometry to double-check that baby's size matches your weeks of pregnancy, which is super helpful especially closer to delivery, so go ahead with it, it's a straightforward ultrasound and nothing to worry about.