The Mad Men star shunned exercise routines and diets to shed the baby weight after her little boy was born in September (11).
And Jones, who has displayed her slender new look while promoting the fifth season of the 1960s drama, found her weight dropped almost immediately because of the responsibilities of motherhood.
She says, ""I haven't been dieting or working out much. I've just been running around, nursing, and keeping busy. That's exercise enough.""
Jones is yet to name the father of her child.