The woman has an asymmetry of her breasts, produced by breastfeeding more or exclusively from the left breast because she works with her right arm and carries the baby on her back with knotted cloth so that the baby is easily placed on the left breast, which hypertrophies to produce enough milk; the right breast stops producing milk and returns to its pre-pregnancy size due to the Lactation-inhibiting factor or IDF (Feedback Inhibitor of Lactation)). If too much milk is left in a breast, the IDF stops the lactocytes from secreting more. This helps to protect the breast from the damaging effects that occur when it is too "full". This happens if the baby stops breastfeeding for any reason.

Although IDF is a substance that is not well known, it helps to understand why:

• If a baby stops suckling from one breast, that breast stops producing milk.

• If a baby sucks more from one breast than the other, that breast produces more milk and gets bigger than the other.

• It is possible to breastfeed from one breast as is done in some cultures: the non-breastfed breast stops secreting despite prolactin and oxytocin.

• For a breast to continue to produce milk, the milk must be withdrawn.

• If a baby cannot suckle from one or both breasts, milk should be withdrawn. by extraction to allow production to continue.