The Truth About Breastfeeding

If you’ve ever felt that your baby isn’t satisfied with your breast milk, you’re not alone: ‘not enough milk’ is the reason mothers provide more than any other for giving up on breastfeeding¹. A recent review in the Journal of Nursing Scholarship reports that the problem is huge²: Insufficient Milk Supply (IMS) is the primary cause of 35% of instances of early breastfeeding termination. If we apply this figure to the UK, where 51% of women start breastfeeding initially, but have stopped by 6 months³, it equates to an alarming 1 in 6 babies being potentially malnourished, were it not for the option of formula milk.

Or does it? The review, which collates the research in this area over the last 10 years, reveals that the term IMS is actually used interchangeably with PIM – Perceived Insufficient Milk – making it very difficult to determine how many women really aren’t providing enough milk for their babies, as opposed to those who just believe they aren’t.

Although research in this area is lacking (according to the review, ‘the accuracy of maternal perceptions, or PIM, in relation to actual milk supply has not been determined’), there is some data that gives an idea of the relationship between the two. A study conducted in Chicago followed 96 mothers who planned to exclusively breastfeed for at least 12 weeks⁴. To determine how much milk their babies were taking on board, the women were asked to weigh them before and after every feed and record the results in a log book. Whether or not the women thought their milk supply was adequate was determined in a series of telephone interviews.

Unfortunately, the paper doesn’t report exactly how the mothers’ perception of their milk supply related to their actual output (the goal of the study was to identify factors that predicted whether women were breast or formula feeding at 12 weeks). It is, however, possible to work out roughly from the data they do include that at least 17% of the women whose supply was adequate at the final recorded weighing session went on to report PIM in the interview two weeks later. Whilst the possibility that the milk supply of all these mothers suddenly dropped cannot be ruled out, neither can the possibility that it was the perception of their supply, rather than their actual supply, which suffered.

One thing that the Chicago study did demonstrate strongly, as did the other research in the review, is that if women think they aren’t producing enough milk (regardless of how accurate this perception is), they are more likely to stop breastfeeding, or supplement with formula. The study also showed that the women most likely to report PIM (and to have a genuinely inadequate supply) were those who breastfed their babies fewer than 8 times a day. As breastfeeding regularly is itself vital to maintain production¹, anything that compromises this (such as formula supplementation) can quickly reduce supply, turning the perception of insufficient milk into a reality. If you’re genuinely worried, you should see your doctor. In the meantime, keep in mind that the best way to stop supply dwindling is to increase, rather than decrease, the frequency of your breastfeeding.

For further information about this problem, see not enough milk: the ‘symptoms’ you don’t need to worry about.

At the end of the study (12 weeks postpartum), 28 mothers were using formula either completely or partially, and 69 were breastfeeding exclusively. At week 6, (when actual milk output was calculated for the final time), 19 of the formula feeders, and 65 of the breastfeeders were shown to have an adequate supply. In the 8 week interview, however, 20 of the formula feeders and 6 of the breastfeeders reported PIM, which means that assuming that the 13 women whose supply was genuinely low at week 6 reported PIM at week 8, the other 13 mothers (11 formula feeders and 2 breastfeeders) perceived their supply to be low when not long before it had been shown to be fine. Unfortunately, as the measures of actual and perceived insufficiency weren’t taken at the same time, it isn’t possible to work out exactly how much of the insufficiency is imagined rather than real (more research in this area please!). On the plus side, 6 women who reported PIM at week 8 were breastfeeding exclusively at week 12, so it isn’t impossible to overcome this problem.

1. Aust Fam Physician. 2006 Sep;35(9):686-9.
2. J Nurs Scholarsh. 2008;40(4):355-63.
3. Infant Feeding Survey 2005
4. J Perinat Neonatal Nurs. 2007 Jul-Sep;21(3):250-5.