Probable incidence of genuine low milk supply
As is well known, breast milk production is regulated by the process of 'supply-&-demand', so if there is inadequate 'demand' there will be inadequate 'supply'. Inadequate demand can take many forms, but crucially, perhaps the most important form is dependent on the baby's ability to access and remove synthesised milk. Any milk which is not removed will be interpeted by the breasts as 'not needed', will be re-absorbed, and milk supply down-regulated as a consequence. The down-regulation of milk supply in the first 4-6 weeks post-natally remains a largely unexplored, but potentially insidious cause of perceived breast milk insufficiency (PBMI); also referred to as self-reported insufficient milk (SRIM), Perez-Escamilla et al, 2019 (Click here for link to article).
The article attached was based on a Medical Research Council (MRC) funded research study aimed at investigating clinical problems of breastfeeding, specifically of low milk supply; it remains my best estimate of the probable incidence of insufficient milk supply in the general population, even though it is based on a professionally-referred clinical population.
Several issues need to be emphasised. First, because this was clinically-referred population of clients, several dedicated community healthcare professionals (M/ws, HVs, GPs) had already made a substantial input. As a consequence, 95% of referrals for low milk supply reported reliable, verifiable symptoms. Despite this, 85% of referrals for low milk supply were resolved by routine, higher-order recommendations - addressing the frequency or patterning of feeds; anatomical details of positioning and attachment; and by providing ongoing support and encouragement.
This leaves 15% of cases referred for low milk supply which were not routinely resolvable, and most will have necessitated given artificial formula to alleviate undersupply and poor infant growth. But within this 15% there were four distinct classes of problem, of which only two represent a biological predisposition to low milk supply, while two were avoidable and both should have, and could have, been avoided with more optimal management in the early days post-natally.
Of this 15%, only 1.3% represented a 'clinical patho-physiology' of the mother (or baby) which prevented an adequate milk supply being available. There was no duplication of any single entity, making it difficult to generalise from these cases. Nonetheless, milk intake was typically below 150g/24hr; in one case, being just 18ml for over 4 hours of suckling (the milk composition being normal, no elevated levels of any component, e.g. sodium). Clearly supplementation with formula is vital in such circumstances, but ALL mothers in this position continued to put their baby to the breast for whatever benefits they or their baby might achieve (immunity, fertility control, affectionate ties, closeness & reassurance of the infant). NB This group included one case of suspected Addison's Disease of the mother, and one case of Noonan's syndrome in the baby - neither of which represent a primary pathology of milk synthesis, on their own, but which is a secondary consequence of the primary condition.
Within the larger group, 4.6% of mothers suffered from genuine 'Physiological low milk supply', necessitating supplementation with formula to ensure adequate infant growth. In other words we were unable to boost supply in these mothers by routine technical advice; by changes to the patterning of feeds; by adjunctive pumping; and/or by use of pharmacological agents (under close supervision - including monitoring of maternal prolactin levels). Practically, these mother were producing between 150-350 g/24hr of breast milk, which falls below the 1st centile for milk supply (i.e. 'normal' for 1% of the population).
So, in summary, a total of 6% of cases referred for low milk supply (4.6%+1.3%) were proven as being real, and were unresolvable by routine measures. It is difficult to conceive of this percentage translating into a similar proportion of cases in the general population, so the probability of genuine low milk supply is likely to be under 5%.
There were two separate categories: 'Iatrogenic low milk supply' (2.6%) and 'Behavioural low milk supply' (2.6%), both of which do not represent physiological cases of low milk supply, but ones which have been acquired through the early mismanagement of breastfeeding. In such cases it appeared that there had been irreversible down-regulation of milk supply from an earlier higher level, but that once this had happened, it was not possible to reverse by routine methods. This also means that 5.2% of cases of low milk supply were the result of inappropriate management of breastfeeding in the early days (in contrast to the large number of mothers who were appropriately managed in the early days).
I leave others to speculate as to what represents the real incidence of genuine low milk supply in the overall population, but I firmly believe that estimates of 5-10% are wildy wrong - hence my claim that breastfeeding works for 98% of mothers (if correctly encouraged/managed).
Click here for link to pdf file