Rear-ended

Hannah

Yesterday on my way to work, (first day, and haven't worked entire pregnancy) but my mom was driving and traffic started to stop and the lady behind us wasn't paying attention. Got rear-ended and obviously I'm watching for bleeding, leaking, and movement all day as well as calling my doctor. Finally, I received a call back today and got an US. They said he's 4lbs is that huge for 31 weeks? Thankfully everything is normal, just curious.