The Russell Silver Foundation site has a list of symptoms and compares "SGA" (small for gestational age) babies to Russell Silver babies.

These babies are all very small. There are many other signs that are easy to miss.

At least two infants in PAGER who failed to gain weight were later discovered to have Russell Silver Syndrome.

http://coltongeorge.com/html/russel_silver.html

Check with your
doctor first!