The second child born to Dena (Vallem) and Axel Thompson was LaVern, on July 15, 1913 in Chicago, Illinois.
Here is a copy of the Cook County birth certificate. Note the first name is "Baby" Thompson. Occasionally I've run into a birth record where the parents had not yet named their child so the county has usually left it blank. This is the first name I've encountered "baby", which is pretty obvious.
Page 1 of the birth register (entry #21633).
Page 2 of the birth register (33rd line).