Placental maturity to grade 3 is good as per your period of gestation, so don't worry about the pregnancy sustainability. It's the fetal growth what matters most. If your fetal growth is as per your dates, then rest is fine
Next Steps
If dates & sonography are showing discordance in fetal growth i.e fetal growth restriction, then go for Colour Doppler.
Health Tips
Moniter fetal movements properly.