Are you still worry about the winter for your baby, here are the shoes you need for your little ones. 
These shoes are comfortable, it is a good start for baby learn how to walk too.
Warm lining, comfortable
Size: US4.5--Inner length: 11.6cm 4.625inches ; US 5-Inner length: 12.1cm 4.75inches; US5.5---Inner length: 12.6cm 5inches ; US6-6.5---Inner length: 13.1cm 5.16inches; US7---Inner length: 11.6cm 4.625inches ; 13.6cm 5.5inches
About the size, it's better to measure your baby's feet, and follow the INNER length we have in CM.
The best size for your baby would be, her/his feet real size plus 0.5 to 1cm then become the inner /insole size.
The internal length is manual measurement which might have about 0.5cm difference.