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Foremilk and hindmilk – all you need to know

If you’ve ever heard people talking about foremilk and hindmilk, I’ll forgive you if you’re feeling a bit bewildered. Since when do you make different kinds of milk? And the advice that comes with it is often equally confusing: “If your baby has green poops, it means he’s getting too much foremilk” – I thought I was only giving breast milk?! Or “you must keep baby on the breast long enough to get the hindmilk” – and how long is that? Besides, I thought we weren’t supposed to be timing baby’s feeds?

The whole concept of foremilk and hindmilk is very useful to explain some of the dynamics of breastfeeding, but unfortunately the message has gotten a bit garbled. In this post, I will try to separate the fact from the fiction and help you understand how this is relevant to your breastfeeding journey.

What is foremilk and hindmilk?

First of all, let’s clear up a major misconception: foremilk and hindmilk are not two different types of milk. The terms were coined to describe the differences in milk composition that occur during the course of a feed:

  • If you express milk before a feed, you will notice that the milk is quite watery, sometimes even blueish in colour. This is the so-called foremilk. Foremilk is relatively higher in water and lower in fat.
  • If you express milk after a feed, you will notice the milk is a lot creamier; it will be opaque white or even yellowish. This is the so-called hindmilk. It is much higher in fat – it has at least twice as much fat as the foremilk, and often three times as much or more.

Where we go wrong is in seeing foremilk and hindmilk as two distinct “types” of milk. But as I will explain, they’re just the same milk seen at two different times.

The fat level in breast milk changes during a feed

Your breast doesn’t suddenly change from making foremilk to making hindmilk at some random point during the feed. Instead, the fat content of the milk gradually increases throughout the course of the feed. So if you were to express some milk in the middle of the feed, you would see that it is somewhere between the creaminess level of the foremilk and the hindmilk. La Leche League have a great way of explaining this in the Womanly Art of Breastfeeding: at the beginning of the feed, it’s like your baby is drinking skim milk. As baby drinks, the milk becomes fattier and creamier – so then it becomes like low-fat milk, then full-cream milk and then half-and-half. So the closer the baby gets to emptying the breast, the fattier the milk becomes.

Why does the milk fat content change?

How does this work? Simple: milk fat is sticky. If you’ve ever pumped breast milk and left it to stand, you’ll know that the cream floats to the top and sticks to the bottle, and it can be really difficult to get it all mixed in again. Well, something similar happens in the breast: the milk fat sticks to the sides of the breast ducts. At the beginning of a feed, when the breast is still full, the milk flows out easily and doesn’t pull a lot of the fat with it – this is why the first milk is so watery and low in fat. As baby keeps drinking and the breast becomes emptier, more and more of the fat is “pulled along” into the milk, and the milk gradually gets creamier. So the milk at the end of a feed is creamier and higher in fat than the milk at the beginning of the feed.

Other factors affecting milk fat content

Interestingly, there are also other factors that influence how much fat there is in the milk:

  • How full the breast is: The fuller the breast is, the bigger the difference in fat content between the foremilk and hindmilk. You will notice if you pump from a very full breast the first milk is much more watery than when the breast is emptier.
  • How long it has been since the last feed: this goes hand in hand with the previous point. If baby feeds at short intervals, the foremilk is likely to have a higher fat content than if baby feeds at long intervals. (In my head it works like this: if the milk has been in the breast for a long time, the cream has more time to separate out and stick to the sides of the ducts. Like when a bottle of pumped milk has been standing in the fridge for a few hours. In reality it probably doesn’t work like that, but it makes sense in my mind).
  • Duration of feeds: this one makes sense if you understand that the fat content in the milk changes gradually. The longer baby stays on one breast, the more fatty and creamy the milk becomes.
  • Length of pregnancy: if your baby was born prematurely, the average fat content of your milk overall is about 30 percent higher. Nature knows that premies need all the help they can get.
  • Age of the baby: interestingly, the breast milk of women who have been lactating for more than a year is substantially higher in fat. Again, I suspect this is nature’s way of compensating for the fact that toddlers are doing a lot of growing, yet they’re often not that interested in eating.
  • Breast massage: there’s some speculation that massaging the breast can “release” more milk fat into the milk. Again, in my mind, this is like shaking up that bottle of expressed milk. A recent study also showed that hand expressing yields milk with a higher fat content than pumping, and this is thought to be the reason.

You will notice that “mom’s diet” does not appear on that list. The fat that you eat will determine the kind of fat in your breast milk (e.g. if you eat a lot of omega 3 fats, your milk contains more omega 3, and if you eat a lot of saturated fat, your milk is higher in saturated fats. Yet another reason to avoid trans fats!) but the amount of fat in your breast milk is completely independent of what you’re eating. So there’s no point in eating lots of fat to try and make “richer” milk.

Balancing foremilk and hindmilk

This is where everyone starts to panic: how do I make sure than my baby gets in enough of the hindmilk? Fortunately, in most cases, you really don’t have to worry about it. Your body and your baby will adjust to each other so that baby gets in enough fat overall – that’s the wonder of breastfeeding on demand. So if all is going well with your baby, you can immediately stop worrying about foremilk and hindmilk, and just enjoy your breastfeeding relationship. However, it does sometimes happen that babies get too much foremilk, or you want to give extra hindmilk for some reason. I’ll look at two such scenarios next.

Oversupply and lactose overload

Although every breastfeeding mom dreads not having enough milk, having too much can be just as much of a headache. In cases where there is an oversupply of milk, baby may never empty the breast enough to get to the “hindmilk” – in other words, there’s so much milk in the breast that baby’s tummy is full before he gets to the higher fat milk. Oversupply is a complex problem that deserves a post all on its own (read about it here). In the context of foremilk and hindmilk, oversupply causes your baby to get only foremilk: because there’s such a lot of milk, baby’s tummy is full long before he gets to the fattier milk. All this high-lactose, low-fat milk causes a lactose overload – which leads to nasty, smelly, slimy green stools. Baby may also show poor weight gain, since he doesn’t get enough fat.

To fix this problem, you want to make sure baby spends enough time at each breast to empty it. If you have a very high milk supply, baby may not be able to drain the breast during one feed. In that case, you may need to do two or more feeds in a row from the one breast –keep using only the one breast until it is soft and fairly empty. (While you are doing that, you can express a bit of milk from the other side if it gets uncomfortable – you don’t want to end up with engorgement!). Once the first side has been drained, switch sides and repeat the process. This is called block feeding, and it usually sorts out the problem within a day or two.

Of course, you can also create a scenario where baby gets only foremilk if you restrict baby’s time at the breast – say, only allowing baby to drink for five minutes at each side. This is just one reason why it’s important to always follow baby’s lead for breastfeeding!

Feeding hindmilk to boost weight gain

The other scenario where foremilk and hindmilk become important is when a baby is not gaining weight well. Sometimes, we can fix that by ensuring that baby gets a higher dose of high-fat hindmilk. I’ve often used hindmilk feeding to improve weight gain in premature babies. If you are pumping, it’s simple: you pump for 2-3 minutes after the first let-down, and store that milk in a bottle labelled “foremilk”. Then you pump again, and store that milk in a bottle labelled “hindmilk”. The milk from the hindmilk bottle is what we then feed to the baby. Alternatively, you can pump a bit to remove the foremilk, then breastfeed (so that baby is getting high-fat milk straight from the breast), and then pump again to collect the hindmilk. You can even take it further: pump extra milk afterwards, allow the milk to separate, and then skim off the cream and feed that to baby. The extra fat intake can make a big difference to weight gain.

Practical implications

So where does all this leave us? As I mentioned before, you rarely need to worry about whether your baby is getting the “right” mix of foremilk and hindmilk. You’ll probably be fine if you just follow these two simple guidelines:

  1. Let baby finish the first breast before offering the second. That way, you know baby is getting all the fat from that breast.
  2. Let baby set the pace. If you allow baby to feed as often and for as long as he likes, you’re not likely to have any major hassles. For more information on how breastfeeding on demand works, check out this post.

If you follow these two guidelines, you’re unlikely to have any problems; you can forget about the technicalities of foremilk and hindmilk, and just enjoy breastfeeding your baby.

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