IUGR?

Vanessa
Went for my 35 week appointment and the ultrasound tech stated that baby is 4lbs 2oz. The last time they estimated a weight was when I was 30 weeks and he was 3lbs 1oz. So he only gained 1lb in 5weeks. I'm already high risk and in bed rest since 30 weeks because of incompetent cervix. Now this. The doctor made an appointment for me to go to the hospital for a high risk ultrasound to rule out IUGR. 
My questions/concern if it is IUGR: truly what is it? Can I still have a vaginal delivery? Will my baby be healthy? Are there any long term effects of IUGR that I should be prepared to handle after delivery? 
Any advice or help on this topic will be greatly appreciated.