You’ll return to your pre-pregnancy cup size a year after giving birth… even if you’re still breastfeeding

bra and pants

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.

  1. Exp Physiol. 1999 Mar;84(2):435-47.
  2. J Pediatr Gastroenterol Nutr. 1987 Sep-Oct;6(5):758-63.
  3. Exp Physiol. 1992 Jan;77(1):79-87.

Where does fore-milk end and hind-milk begin (and does it actually matter?)

milk-creamAccording to the World Health Organization, breastfeeding provides all the nutrition your baby requires for the first six months of life. This entails satisfying both hunger and thirst, and to meet both these needs you might have heard that your breasts produce two distinct types of milk: thin, watery ‘fore-milk’ to quench thirst; and creamy, calorie-rich ‘hind-milk’ to satisfy hunger.

These apparently different types of breast milk are described in various ways, but a distinction is generally drawn between a watery/creamy consistency, and thirst/hunger. There is also an implication that you need to make sure your baby gets enough hind-milk in order to gain weight. According to DrPaul.com:

‘Foremilk is the milk which is first drawn during a feeding. It is generally thin and lower in fat content, satisfying the baby’s thirst and liquid needs.
Hindmilk is the milk which follows foremilk during a feeding. It is richer in fat content and is high in calories. The high fat and calorie content of this milk is important for your baby’s health and continuing growth.’

ParentingWeb.com carries a similar description:

‘Foremilk, a bluish-white milk that is lower in fat than the hindmilk is the milk your baby receives in the first part of the feeding.
The hindmilk, which follows the foremilk, is richer and higher in fat than the foremilk. The hindmilk provides most of the nutrients your baby needs to gain weight and grow, and it satisfies his hunger.’

Valorie Delp on Families.com goes a step further, and says you can actually see the difference between the two:

‘If you’re really into science, pump a bottle of milk and let it sit out on the counter for awhile. You’ll see the milk separate into two distinctive layers. . .one being much fattier than the other. That’s hind milk and foremilk.’

Valorie’s demonstration is appealing, but it’s unfortunately some way off the mark. The separation she describes is simply the fat in the milk rising to the surface, not a different type of milk. This illustrates quite neatly the problem with using the terms ‘fore’ and ‘hind’: it reinforces the impression that the breast produces two types of milk, when in fact it makes only one. The descriptions shown above aren’t entirely inaccurate – milk does indeed change consistency during a feed – but this happens gradually, rather than suddenly.

The change occurs due to an increase in the fat content of the milk as a feed progresses – hence the ‘creamy’ label attached to hind-milk. It isn’t simply the case of the longer the feed, the fattier the milk, however. A study published in Experimental Physiology demonstrates that the fat content is related to the ‘emptiness’ of the breast: the less milk it contains, the greater the proportion of fat in the milk1. This means that if a baby has a 4oz feed when the breast is only storing half its potential milk volume, it will contain more fat than a 4oz feed taken when the breast is three-quarters full.

The amount of fat in your milk therefore varies considerably throughout the day, depending on the time since the last feed, the amount of milk consumed at the last feed, the amount of milk consumed at the current feed… It sounds complicated – how on earth do you make sure that your baby is getting enough? The short answer is that you don’t need to. Whilst fat is an important constituent of your baby’s diet, so are protein and carbohydrate, and both of these are found in the watery rather than the fatty part of the milk. The evidence also suggests that weight gain is related simply to the volume of milk consumed, and not its fat content2, underlining the nutritional importance of all the components of breast milk.

If you are breastfeeding on demand, the bottom line is that you don’t need to worry about the ‘type’ of milk your baby is getting. Babies can show a wide variety of feeding patterns, suckling for varying lengths of time and at varying intervals over the course of a day, and maintain a healthy weight3. The terms ‘fore-milk’ and ‘hind-milk’ do have their place: in scientific studies, they are used to describe the samples of milk taken at the beginning and end of a feed. In more general usage, however, they often produce a confused and inaccurate picture. They split milk into two types (when there is actually only one), and imply that the fat contained in milk is somehow more nutritious than the rest of it. In fact, nutrients that are important for health and growth are contained in both components of breast milk, so the implication that the fatty part is for ‘eating’ and the watery part for ‘drinking’ is somewhat misleading. The important thing to remember is that ensuring your baby’s thirst and appetite are satisfied is not a complicated undertaking – it’s simply a matter of letting her feed when she wants to.

  1. Exp Physiol. 1993 Nov;78(6):741-55.
  2. Paediatr Perinat Epidemiol. 2002 Oct;16(4):355-60.
  3. Pediatrics. 2006 Mar;117(3):e387-95.Click here to read
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