El Congo francés es la actual República del Congo.

La mujer situada a la izquierda muestra una asimetría de sus pechos, probablemente producida por amamantar más o exclusivamente del pecho izquierdo debido a que trabaja con el brazo derecho y carga al bebé en su cadera izquierda. El pecho izquierdo se hipertrofia para producir la leche suficiente y el derecho deja de producir leche y vuelve al tamaño pre-embarazo debido al 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• For a breast to continue to produce milk, the milk must be withdrawn.

• If a baby cannot suckle from one or both breasts, milk should be withdrawn.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.