Baby dropped in percentile for growth.

Today we had our 36 week ultrasound the last time we had one was at 32 weeks. At 32 weeks baby was measuring great estimated weight was 3lbs 15ozs and was in the 47th percentile for growth and my belly was measuring perfectly at 32in. Today at our 36 week appointment we found out that babies estimated weight is 5lbs 5oz but he has dropped to the 23rd percentile in growth, when my OB measured me I was still at 32in and they became concerned because my stomach stopped growing and he dropped considerably. We now have another ultrasound next week at 37 weeks and meet with 2 OBS, if they suggest taking him early I'm going to say yes. My now 6.5 year old was born 3 weeks early due to the same growing restrictions that I had encountered and he weighed 5lbs 3ozs and was as healthy as can be. I'm a little nervous as to I thought we had 3 weeks but now possibly we don't even have that.