Europeans have always used Sleep Bags to keep their little ones covered and warm.
They do not meet US sleepwear regulations (no fire retardants) and so we must
recommend that you only use them only for lounging. 

WHAT WARMTH BAG DO I NEED?  
WARM WEIGHT (Velour, Wool, & Quilted fabric) is best for sleeping in 61F-71F (16c-22c)
Cotton Quilted is the warmest, followed by Alpaca & Velour.
MID WEIGHT  (Interlock Jersey Fabric) is best for sleeping in 70F-76F (21c-25c)

More about TOGs and how to dress your child when wearing a sleep sack - click here.

HOW TO TELL IF YOUR CHILD IS WARM ENOUGH:
 Your baby can't regulate her temperature at first, so dress her in one more layer than
you would wear and check her temperature by feeling the back of her neck with the back of your hand.