bedrest/steroid shot?

i went into the hospital when i was 31 weeks and was 2cm dilated and having contractions. while i was there they gave me 2 steroid shots to make sure his lungs would be strong enough if i gave birth. i ended up not giving birth and now i’m on strict bedrest and im almost 34 weeks. my doctor is doing an ultrasound next week to see how much he weighs, but is there a reason why she’s checking? can the steroid shots i got affect his weight? could he be growing too fast now? i want to go to at least 35/36 weeks but i’m not sure how likely it is. help!