For many women, an increase in cup size as breasts get ready for providing food is one of the first signs of pregnancy. After giving birth, they expand even further as they fill up with milk, but even after a feed, they remain bigger than they were previously, due to the increase in breast tissue required for milk production.
If you continue to breastfeed after solids have been introduced and cut down gradually, your breasts will slowly decrease in size, until you get to the point where you fit back into your old bras. At this point, you’d be forgiven for thinking they can’t possibly be providing your baby with much sustenance, but in fact they are probably doing more than you think. An intriguing article published in Experimental Physiology shows that whilst breast size is related to to the amount of milk produced for the first 12 months of breastfeeding, after this point breasts return to and stay at their pre-pregnancy size, even if they are still manufacturing milk1.
The study followed 8 mothers who breastfed exclusively for 6 months, and weaned after 18 months. Milk production over a 24 hour period was measured by test-weighing the mother2 and breast volume (their actual size minus the amount of milk produced) was calculated using a special ‘Computerized Breast Measurement’ system3 at 1, 2, 4 and 6 months after giving birth, and then at three monthly intervals until weaning.
Milk production – and breast volume – remained constant for the first 6 months, and both started to decline after this point as other food was introduced. By 15 months, however, breast volume had reduced to the level it was before the women gave birth, and remained at this point from then on even though the mothers were still producing on average 200g of milk a day. When the mothers weaned their babies completely, there was no significant further reduction in breast size.
The authors state that this occurs because breasts become able to make milk more efficiently: although an increase in breast tissue is necessary to initiate and sustain a high level of milk production, when it naturally declines as milk output falls, the remaining tissue is still able to produce a significant amount of milk.
For any mothers who are nursing past the 12 month mark but sceptical that their breasts are still up to the job, this will make interesting reading. Even though it may sometimes seem as if you don’t have anything left for milk production, the chances are you’re more than capable.
- Exp Physiol. 1999 Mar;84(2):435-47.
- J Pediatr Gastroenterol Nutr. 1987 Sep-Oct;6(5):758-63.
- Exp Physiol. 1992 Jan;77(1):79-87.