"Las Dos" and breastfeeding diversity

"Las Dos" 
"Las dos" (meaning "both") is a phrase used among many Hispanic women to describe the common practice of using formula supplementation alongside breastfeeding--not necessarily out of dire need but more as a matter of preference or culture. Many Hispanic women feel that "las dos" offers them and their babies the best of both worlds--they feel that their milk may not be enough, that formula will offer extra vitamins or that breastfeeding is just more convenient this way.

"Las dos" was recently discussed by the breastfeeding advocacy site Best for Babes, picking up from a 2010 poster campaign run by the Massachusetts Breastfeeding Coalition (scroll down to see). The posters urged Hispanic women to breastfeed exclusively, with the legends "Both Breast and Bottle? No!" and "If you give me formula, you won't produce enough milk for me/Your milk is full of important vitamins" in Spanish or English, accompanied by either a worried-looking baby or a picture of smiling breasts versus a bottle with a frowny face. Not a lot of room for ambiguity there, then.

The Best for Babes write-up covers the familiar territory: "But the problem with doing 'las dos' is that it deprives the baby of the benefits of exclusive breastfeeding, and it creates problems with the mother’s milk supply." ("It creates problems," mind you; not "It's possible it could create problems" or "It can create problems for certain women" or "Excessive supplementation creates problems.") We all know roughly what the argument is here: because breastfeeding is supply and demand, giving any formula at all is apt to lead the mother down the "slippery slope" of ever-increasing formula usage. Best for Babes suggested that women who practice "las dos" do so because they don't know better--a suggestion echoed by the study linked to on the same page, "Las Dos Cosas: An Analysis of Attitudes of Latina Women on Non-Exclusive Breastfeeding." (But don't worry; the study noted that "Women consistently demonstrated a willingness to learn from health professionals" about the need to avoid supplementation. So that's alright then.)

How true are the claims?
Now, the whole debate about the benefits of exclusive breastfeeding and how much greater these are compared to supplementing is a complicated one and I won't go into it in full here. I'll just say this: Exclusive breastfeeding to six months matters a lot in developing countries where a single serving of porridge/formula etc. made with contaminated water can kill a vulnerable baby. In developed countries, the benefits are likely to be "modest" and much harder to quantify.

I want to focus on the claim that adding-in formula causes supply issues (the "slippery slope" argument). The  trouble is, the evidence that combo-feeding causes supply problems in Hispanic women is actually kind of weak. For one thing, there's the awkward fact that in spite of frequently preferring to add in some formula, Hispanic women consistently show the highest rates of breastfeeding of any racial group in the United States, as long as the criteria used is "any breastfeeding" rather than exclusive breastfeeding.

What about if you compare Hispanic women who do supplement with those who don't? Linda Geddes looked at this area in her excellent book Bumpology. There's a dearth of evidence on the subject, but there is a 2005 analysis of 6,788 mother/child pairs of various races which found that "65% of the infants who were exclusively breastfed were still receiving any breastfeeding at 4 months compared with only 40% of the children who were fed a combination of breast milk and infant formula during the first week of life" but that "CBFF [combination breast milk and formula-feeding] is associated with shorter overall breast-feeding duration in white but not Hispanic or black mother-baby dyads." So for the babies overall, supplementing with formula early on significantly increases the chance that the mother stops nursing altogether--but for the non-white babies, this seems not to be the case, with those who get formula supplements being just as likely to go on breastfeeding as those that do not.

It tends to be the same story across many ethnic minorities in majority-white countries (African-American women being an important exception (Note 1)). In the United Kingdom, white women have the lowest breastfeeding rates of all racial groups (Note 2), while any-breastfeeding rates and predominant-breastfeeding rates are highest of all for African immigrant women (Zimbabwean, Somali etc.) followed by a tie between Asian (Note 3) and Afro-Caribbean women. But the exclusive-breastfeeding-to-six-months rate is low for all these groups because so many women do things like give formula till their milk comes in, add-in some formula even after that, or start solids before six months. Among Somali women in particular, comparing breastfeeding cessation rates for combo vs exclusive feeders would be tricky because supplementing is so normal that it's hard to find a control group. And exceptionally high numbers of Somali women breastfeed--around 90-95%. In Japan too we have high rates of predominant breastfeeding yet low rates of exclusive breastfeeding--most women add in some formula.

I once talked to a maternity ward nurse who worked in a London hospital where there were a lot of Somali mums, and I asked her if there was any conflict between the NHS's focus on exclusive breastfeeding versus the Somali mums' preference for supplementation. She laughed and said "The new nurses try and talk the mums out of supplementing at first. And then after a while they shut up, because they start to realize that the mums are a) taking no notice, and b) doing a good job of breastfeeding anyway, even though they're technically breaking all the 'rules.'"

Why might white women have more difficulties combo-feeding?
If combo-feeding is indeed more difficult  for white women than for other races, why would that be? There could be some kind of biological mechanism going on, but there could also be cultural explanations.

One possibility is that among white women, adding-in formula is not a cause of breastfeeding issues, but rather is a "marker" for women who tend to have breastfeeding/supply issues anyway. The theory goes something like this: "White" breastfeeding culture (which tends to be dominated by books, lactation consultants and the LLL) places a strong emphasis on exclusive breastfeeding and this is presented to white women as the ideal. So women avoid adding-in formula unless things are going wrong, like supply issues, a baby who isn't latching well or the presence of formula-feeding families/friends who pressure the mother to add some bottles to "fill him up." So when you look at the two groups, the "exclusive breastfeeding" group contains mostly women who find breastfeeding easy anyway, and the "combo-feeding group" has lots of ladies who have supply issues and other problems or are surrounded by unsupportive formula feeders... and maybe it's these issues that are causing them to give up, not the "slippery slope" of the formula itself. Among Hispanic, Zimbabwean etc. women (so the theory goes), combo-feeding is not seen as second-best and so the decision to combo-feed tends not to be strongly correlated with the existence of breastfeeding "problems."

Another possibility is that it's to do with confidence and normalization. If a Hispanic, Somali etc. woman thinks of breastfeeding as normal, when faced with issues she may take the pragmatic attitude of "Let's see if I can mix things up a little." A white Anglo woman may be surrounded by stronger external pressures to formula-feed--if she experiences difficulties she may be more likely to see breastfeeding itself as the cause of her worries, and feel that the best thing to do for her sanity is to cease nursing altogether. She may not have successful combo-feeders among her peers; if she is getting her breastfeeding knowledge and support primarily from online fora and lactation consultants, attempts to discuss combo-feeding may just result in lectures rather than practical advice. Perhaps white breastfeeding culture's emphasis on the "slippery slope"makes a struggling breastfeeder feel that attempts at combo-feeding are doomed to fail anyway and will just add to her stress.

A final possibility is that certain childrearing practices make combo-feeding easier, or are so supportive of breastfeeding that they "make up for" any issues that combo-feeding might create. In my thoughts on breastfeeding in Japan, I mused that the widespread practice of bedsharing (and frequent night-nursing) might be why widespread formula supplementation, low nursing-in-public levels and rigid, old-fashioned hospital routines don't seem to send Japanese women's breastfeeding into a tailspin. Bedsharing is commoner among Hispanic America, African immigrant, British Asian and Afro-Caribbean women than among white women, so perhaps this is worth looking into. Other practices like extended periods of post-partum rest following childbirth, common in several cultures, also merit investigation.

So much to talk about
We have a situation where the highest breastfeeding rates in both the UK and the US are found among non-white ethnic minorities, and in the UK in particular white women are less likely than any other racial group to breastfeed...and yet mainstream breastfeeding advocacy remains very white. In general, breastfeeding advocates' response to the non-white minorities where breastfeeding rates are high has been either to a) Ignore them; or b) Complain that the minorities in question aren't breastfeeding "properly" (because they give solid foods too early or add in formula), and then advise the minorities in question on how to breastfeed in the "approved" way. The Best for Babes article does have some really interesting discussion on how American hospitals and ways in which hospitals have tried to cater to Cambodian-, Chinese- and Mexican-American women's needs, and mentions that Hispanic women initiate breastfeeding more often than white women, yet skirts over the fact that they are also much more likely to still be breastfeeding at six or 12 months. Black Breastfeeding Week in the United States a few months ago provoked some great discussion about the barriers faced by African-American women hoping to breastfeed, but there was surprisingly little discussion of the fact that other groups of black women in America already have very high breastfeeding rates and are highly confident in their breastfeeding abilities.

Wouldn't it be good if these women's voices were reflected more in conversations about infant feeding? I'm curious to know how women from Laos or Nigeria or Somalia feel about the breastfeeding advice they are getting in English-speaking countries. Is it helpful? Is it annoying? Does it allow for individual and cultural preferences? If breastfeeding rates are high among certain groups, wouldn't it be great to start analyzing why they are high? And combo-feeding can be a Godsend to women working outside the home; if we want to develop good guidelines on how to combo-feed, perhaps breastfeeding advocacy needs to be getting more input from groups of women who are already combo-feeding successfully...?

What diversity really means

So many ways to breastfeed---including, apparently, 
with breasts made out of multicolored fun-fur

Although the question of "how much better is exclusive breastfeeding than combo feeding" is complex, in developed countries the differences are unlikely to be large enough to justify the Massachusetts Breastfeeding Coalition's approach of basically ordering everyone to exclusively breastfeed, without pausing to consider cultural
differences and individual preferences, as though the feelings of mothers counted for absolutely nothing. And while the question of whether combo-feeding increases the risk of giving up breastfeeding is not 100% clear, there is enough uncertainty surrounding the issue that the blanket statements of the Massachusetts' advocacy materials--"Breast and Bottle? No!""If you give me formula, you won't produce enough milk for me"--sound pretty bossy and over-the-top.

What we really need is more research on what's going on with combo-feeding and breastfeeding styles among women of various ethnic backgrounds. In the meantime, if some Hispanic women prefer to supplement, I suggest that the Powers That Be in hospitals and elsewhere respect their choice and give them the best advice we have at the moment--like making sure women have the basic facts straight (if a woman is combo-feeding purely because she thinks her baby won't get enough vitamins from breastmilk alone, it's surely reasonable to inform her that that's unlikely to be the case), teaching women how to keep an eye on their supply so that formula use does not keep creeping up and up, and making sure that women understand how to prep and feed bottles in an optimal manner--an area the National Association of Hispanic Nurses is now focusing on. True diversity is not about putting a few token non-white faces on display in breastfeeding books and blogs; it's about opening one's mind to the possibility that there could be many ways to breastfeed successfully.

(Note 1) I use "African-American" to refer to black people in the United States who trace their origins to African slaves in that country, while "Afro-Caribbean" refers to black people in the US and UK whose immediate origins are in the Caribbean rather Africa--i.e. they or their parents etc. migrated from there. I use "African immigrant" to refer to black people who migrated from Africa or whose parents or grandparents did so. I'm not thrilled with the term as I don't think someone who has lived in the UK/US all their life can be described to as an "immigrant," but I don't know of any other term that can be used to include all the people in this group.

(Note 2) Except for Romani Gypsies and Irish Travellers

(Note 3) In the UK, most Asian people are of South Asian origin--i.e. their ethnic origins lie in places like Pakistan, India and Bangladesh--rather than East Asian as tends to be commoner in the US.

White elephants in the freezer: The pros and cons of breastmilk stashes

Back in the glory days when Baby Seal was tiny, my "freezer stash" fluctuated, but basically consisted of two to three plastic containers stuffed at crazy angles around the frozen peas. For one thing, I had the tiniest freezer known to man and needed the space for ice cream healthy homemade casseroles and soups. When were you supposed to find time to pump, in between nursing all day long? In any case, I was lucky enough to work freelance at home. I doubt I would have "stashed" at all had it not been for a vague feeling that this was something you were Supposed To Do when you are breastfeeding. My due date club was full of people talking about having dozens or hundreds of ounces in the freezer. Stashing seemed like part of being a proper organized mother--you know, the kind who irons baby clothes and puts her name on the daycare waiting list at five weeks' gestation.

The freezer culture
The "freezer stash" culture seems to have started among mothers who work outside the home. The idea is: since most mothers find that a few pumping breaks stolen out of the working day just aren't enough to keep up with their babies' needs, you pump during your maternity leave to create a "bank" of frozen milk that you can draw on little by little once you're back at work. Once working, you top-up your stash by pumping at the weekends--or even late in the evening, after the baby is (finally!) in bed. However, in the US in particular, freezer stashes have recently started to become common even among stay-at-home-mothers. This seems a bit odd at first glance--does an evening-out a couple of times a week really require a freezerfull of breastmilk?--but the rationale is that you might be forced to wean for medical reasons, you milk could dry up or (gulp) you could be knocked down by a car and killed. Increased milk-sharing opportunities have perhaps added to the feeling that everyone should be creating a freezer stash ("After all, even if you never use it, someone else will always be able to!"). It's not uncommon these days to hear of women putting hundreds or thousands of ounces into the freezer; many are generous donors, helping out other mothers and hospitalized infants.

The idea seems to be that a freezer stash helps you avoid using any formula, and is strongly connected with modern breastfeeding culture's focus on exclusive breastfeeding and avoiding formula completely. That said, wanting to avoid formula isn't always about formula being inherently dangerous. Formula companies aren't very nice organizations and many people don't like the idea of giving them money. Then there is the "My baby may not accept formula if I try it later on" thing. There is the "I prefer not to do dairy products, and soy makes me nervous" thing. Finally, some mothers also envisage this as a way of getting extra breastmilky goodies into their child--they imagine a toddler drinking thawed EBM in a sippy or mixed with cow's milk.

Beware of the scary freezer...

The dark side of the freezer (cue ominous music...)
Conversely, stashing has some downsides too. What you might call "The Dark Side of the Freezer" (and no, I'm not talking about those ancient tupperware containers containing brown goo of unknown origin, or the ice-cubes that taste of stale fish when you add them to your gin and tonic).

- Frozen breastmilk is significantly inferior to the fresh stuff 
The general assumption is that "even frozen breastmilk is always far, far better than formula." But the evidence is actually quite mixed. Frozen breastmilk has about the same amounts of fat, calories, sugar, protein and elements such as zinc as fresh, and many of its impressive immunological components such as lactoferrin, lysozone and IgA also stand up well to freezing. Freezing does, however, destroy cellular activity and antioxidant activity are greatly reduce to. (That said, frozen breastmilk still has more antioxidant activity than formula).

However, the evidence about decreases in vitamins is less positive. A 1983 study found that "Freezing and frozen storage did not significantly affect the levels of biotin, niacin, and folic acid." But in a 2004 meta-analysis (Ezz El Din et al), Vitamin C in milk was reduced by 56.9%  by one week of freezing, Vitamin A by 48.1% and Vitamin E by 28.8%, echoing a 2001 study (Buss et al) which found that Vitamin C decreased to 63% of the starting values after one month and 38% after two months of freezing; there was massive variation, with one sample having 97% of the Vitamin C it started off with, and another, zero. Confusingly, the findings of another study (Bank et al) indicated that breastmilk frozen for three months would provide a baby's recommended allowance of Vitamin C--but not of folic acid.

This doesn't mean frozen breastmilk risks giving your baby malnutrition; babies supplemented with bottles of the stuff do just fine. But then, well, babies supplemented with bottles of formula seem to do fine too. The question is, if frozen EBM is better than formula, then by how much of a margin is it better? Because this margin has to be weighed up against the substantial amounts of time and energy that go into creating large stashes.

- What are the benefits of avoiding all formula?
The freezer stash tends to be intertwined with anxiety about using any formula at all--a sort of icy buffer zone protecting your baby against the Great White Peril. Now, the PROBIT study (still the closest thing we have to a randomized controlled study of breastfeeding versus formula feeding) suggests that exclusive breastfeeding for the first few months confers some health benefits; however, the study looked at mothers who were mainly feeding from the breast, and it's not clear whether these benefits still apply when we are talking about milk that's been pumped, containerized, frozen (and sometimes scalded and cooled as well), frozen, thawed, transported and fed in a bottle.

And the calculation of the benefits must surely shift a bit once a baby starts solids at around 4-6 months. Much of the rationale for exclusive breastfeeding rests upon the theory of the virgin gut (=your baby's insides become irreversibly contaminated once you give a taste of anything except breastmilk); but even if you accept the virgin gut theory as fact, once you've started giving food your baby's virgin gut has been deflowered and taken round the block a few times--they are already having things that aren't breastmilk. If one is giving other dairy products like yoghurt, is there any particular reason not to add a little formula as well if today's pumping fell short of the required quota? I have looked and looked, and have not been able to find any evidence of negative health-related consequences of giving some formula to a baby who is already taking solids. I guess we all feel differently about these things, but... once I started giving Baby Seal solid foods, the "milk question" suddenly felt very different. All of a sudden, formula was just another food--and it was damn useful for mixing with her cereal.

- Your stash might turn out to be unusable (I call these "White Elephant stashes")
Every due date club has at least one mother who pumps away creating a big stash... only to discover her baby won't drink it when thawed because it tastes fishy, soapy or metallic. Some women have high levels of lipase (an enzyme which breaks down fat) in their milk, causing it to develop a strange taste when frozen. You can prevent this flavor by scalding the milk before freezing; unfortunately, most women don't think to test for lipase issues before they start stashing and therefore have no idea of the problem until they already have a freezer full of funky tasting milk. Scalding the milk after thawing makes no difference, by the way.

But even if you don't have lipase issues, babies used to fresh breastmilk often refuse to drink thawed frozen milk because it doesn't taste quite right--just as adults used to regular milk often wrinkle their noses at UHT. Other babies start refusing such milk as they get older. To add insult to injury, some of them are quite happy to drink formula instead. Finally, if you discover after you've built up a big stash that your baby's digestive issues are connected to allergens in your diet (dairy, wheat etc.), your stash is useless unless you can donate it to someone.

- Your stash might be destroyed by a freezer breakdown, power cut or a freezer door accidentally left open
Hours and hours and hours of hard work literally down the drain. This happens All.The.Time.

- Going mad with the pump can jeapordize your current breastfeeding
One well-known problem is that pumping heavily in the first few weeks can lead to oversupply and engorgement--yet women seeking to build freezer stashes are often advised to start pumping just days after giving birth.

- Stashing costs time, effort and emotional energy
Stashing is not just about the pumping itself. It's also about assembling equipment, cleaning and sterilizing, labelling and dating containers, defrosting your milk, stocktaking, organizing and rotating your stash, and doing fiddly things like mixing frozen milk with fresh in various ratios to train your baby to drink the frozen stuff. If you have lipase issues, you'll also need to scald and cool the milk before freezing. Time spent doing this is time which is not being spent taking a stroller walk in the fresh air, rolling around on the floor with your baby, enjoying a glass of wine and a trashy magazine, having a hot shower, chatting with your partner, catching up on sleep, or spending some time with an older child. To misquote Hanna Rosin, "A freezer stash is only free if your time is worth nothing."

You have to feel a bit sorry for American breastfeeders who work outside the home. Most of them get kicked out of hospital when their contractions have barely died away and are expected back at the workplace after a few weeks. And now there's this increasing expectation that they ought be spending a not-insignificant chunk of their brief maternity leaves plastered to the pump--right when they are trying to recover from childbirth and the shock of caring for a newborn. Breastfeeding is sold to women as being an emotionally rewarding experience--but where's the emotional reward in spending your free time trying to squeeze in extra pumping sessions, when you could be enjoying your baby or having a hot bath (or a cold beer)?

- Freezer stashing can become competitive, obsessive and compulsive
With modern, super-efficient double electric pumps, some women put very large amounts of milk into the freezer.

"I have about 1,000 oz and have donated 3,200 oz to other mom's. [My baby] is 14 weeks old. I was pumping a lot when she was in the NICU and then when I was still home with her I pumped after each nursing session for 20 minutes. I've been back to work for two months now. I pump before work, three times at work and once before bed. I pump between 45-55 oz per day and [my baby] only eats 8 oz while I'm at work."

Impressive though these amounts are, only a minority of women with particularly strong supplies are ever going to be able to pump and store that much milk. But when all these big figures are being quoted, before you know it everyone else is peering into their freezers and wondering if they should start trying to fit in a few more pumping sessions--especially when all the talk seems to imply that not having a stash is a really scary situation that actually places your baby in peril.

A lot of stash builders refer to themselves as "hoarders"; this is a joke, of course, but the banter does seem to be cover some genuine anxiety:

"I have a deep freeze just for milk.  I worry each pump may be my last.  I eat oats every morning and gallons of milk.  My lo will be six months.  I have donated over 5000 oz to a mom. I watch my milk drive away and then i worry i may need it for an unidentified issue. I have over 3000 frozen. I make 80 oz a day and I still worry. I need help." 

"I just had my 3rd three weeks ago and have 1,000 oz in my deep freezer. I need to re-apply to donate but, I have to go back to work full time in 4 weeks and I get nervous I won't have enough. I call it a sick obsession! I don't LIKE pumping but, if I don't do it after every feeding I get paranoid I'm going to loose my supply. I'm a bit OCD when it comes to pumping."

Obviously these are extreme cases, but it's common for freezer stashing mothers to express ambiguous attitudes towards their stashes. (See this discussion at Mothers in Medicine, for example.) Some mothers find themselves inexplicably reluctant to actually use the milk they've stashed and feel increasingly anxious as the stock dwindles. They may (like this mother) find themselves grilling their childcare providers about the amounts they've used and pressuring them to use as little as possible, even when there are still tons of milk in the freezer. Some eventually end up with gallons of unused milk that's beyond its use-by date. Others start feeling irritated if their baby doesn't finish every bottle because of the waste, or try to persuade babies to swallow milk that tastes and smells foul because they can't face the thought of throwing it away.

Of course the problem here doesn't lie with the mothers themselves; it lies in the fact that when lactation is turned into a numbers game (the number of ounces you express, the number of pumping sessions, the number of minutes you are allowed for pumping breaks, the number of containers in the freezer, the number of months they've been sitting in there), it's really easy for even the most level-headed mother to become a bit obsessive--especially when you add in the inevitable post-partum craziness and sleep deprivation, and the not-terribly-subtle scaremongering about formula that we see in mothers' groups.

Keeping the White Elephants at bay!
I would recommend that anyone thinking of creating a massive stash rule out potential issues first, before they start to pump, to avoid the frustration of a "White Elephant stash."
- If your baby seems to have digestive issues/colic, hold off on stash building until you have ruled out

Just say no to White Elephant stashes!

the possibility of allergens in your milk.
- Check whether you have lipase issues; if you do you will need to scald all your milk (see here and here).
- Maintain your freezer by using a freezer thermometer and not overstocking (I now blush to think how clueless I have been in this respect).
- Have a backup plan in case the freezer fails. And stick a SHUT THE DOOR note on the door!
-Find whether you actually meet the requirements to donate milk.
-Get your baby used to the flavor of frozen milk early on.

Conversely, employed mothers who don't want to create big freezer stashes need to be okay with using some formula. (Otherwise, they are just exchanging the stress of maternity-leave stashing, for the stress of "Help, help! It's late at night, my baby's screaming, and I need to pump because today I didn't pump enough milk for tomorrow's daycare...") At-home mothers who don't want to stash should remember that things like sudden hospitalization can prevent breastfeeding; better to keep some formula in the house, make sure that one's partner knows how to prepare formula properly, and introduce a little formula early on so that the baby will accept the flavor.

Relishing the experience or shouldering a burden?
I hope this post doesn't come across as excessively negative about freezer stashing. My intention, rather, was to try and redress the balance a bit. There is a lot of talk about big freezer stashes on breastfeeding fora, and many women find them very useful and beneficial; some are also incredibly generous, donating milk to other mothers and to babies in hospitals. But we should also find room to talk about not stashing (and minimal stashing) too, and the benefits and conveniences that that can bring.

Creating a stash is an option, not something breastfeeding mothers have to do. No, even if they are employed full-time.... as long they are content with doing some formula as well. On breastfeeding fora, "having to use formula" often seems to be seen as a sign of failure or disorganization. But it's also possible to embrace such an approach as a conscious and deliberate choice: as an approach that seeks to maximize time spent with your baby, and to make breastfeeding as enjoyable as possible--a delicious experience to be relished rather than a burden to be shouldered.

The final point I'd like to end with is this: When we are comparing expressed breast milk and formula, we can't limit our conversation to what's actually in the bottle. We have to look at the wider context of how it actually got there and how much maternal time, labor and stress went into it. Womens' needs for free time, relaxation, sleep and enjoying motherhood need to be part of the discussion too.  

Freezing milk
Tips for refrigerator freezers
ABM Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants

Lipase issues
The lipase mini-saga from The Adequate Mother

Frozen milk vs fresh
Effect of storage on breast milk antioxidant activity Hanna et al, Archives of Disease in Childhood. Fetal and Neonatal Edition, 2004
Effect of storage time and temperature on folacin and vitamin C levels in term and preterm human milk Bank et al, The American Journal of Clinical Nutrition, 1985
Is stored expressed breast milk an alternative for working Egyptian mothers?   Ezz Al Din et al, Eastern Mediterranean Health Journal, 2004
The effect of processing and storage on key enzymes, B vitamins, and lipids of mature human milk. I. Evaluation of fresh samples and effects of freezing and frozen storage Friend et al, Pediatric Research 1983

Inadvertent Booby Traps from Nursing Freedom: Some interesting discussion about the necessity of freezer stashes

In closing
Trying and Failing to Control Everything and How it Led to Happiness: I love this story!