The struggle to breastfeed is a defining feature of early motherhood for many women.
Of the approximately 90% of mothers in rich countries who start breastfeeding,
a quarter give up within a few weeks,
often because they fear they are not producing enough milk to feed their babies.
For many years doctors have assumed that true cases of poor supply are rare,
occurring in no more than 5% of mothers.
The prevailing advice to worried parents from health authorities in places such as England and America
has, therefore, been to stimulate the release of milk
by either putting the baby to the breast more often or using a breastpump.
This advice, though well-meaning, is turning out to be inadequate.
Many women who follow it still end up with babies who fail to gain enough weight—
a clear sign that the mothers are not producing enough milk.
Studies of breast-milk production involving hundreds of women in America and Australia in recent years
suggest that the proportion of mothers who produce too little milk is far higher than previously thought:
between 10% and 20%.
Researchers are beginning to understand why these numbers are so elevated.
For many women, the explanation lies not in how they breastfeed
but in the composition and function of unique cells in the mammary gland,
an aspect of their biology over which they have no control.
Further research may one day lead to treatments.