18th Percentile at 20 weeks

I am currently 24 weeks and just had my routine visit with my OB. She mentioned that she wanted to do another ultrasound at 30 weeks to check on baby’s weight and development because baby was measuring in the 18th percentile at our 20 week anatomy scan. Should I be concerned? She didn’t seem concerned but this didn’t happen with my pregnancy with our first daughter so it’s throwing me for a loop. Baby’s anatomy was all good on the scan, her heartbeat was normal today, and my fundal measurements were on target at 24 weeks today. I’m trying not to worry.

Anyone else in a similar situation?