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From:
Joy Anderson <[log in to unmask]>
Reply To:
Lactation Information and Discussion <[log in to unmask]>
Date:
Sun, 10 Jan 1999 21:56:18 +0800
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>when bf is truly well-established  it becomes part of the autocrine system
>- it's not dependent on prolactin any more (endocrine) and in most
>lactating women prolacatin levels are back to pre-pregnancy levels after
>several months of bf. Milk is made in response to the baby's sucking so
>most of the milk is made as and when the baby feeds (though there is always
>*some* milk there).

Heather, your first sentence above is certainly true. However, it is now
known that milk is not made in response to baby's sucking - it is made
continuously and at a rate determined by the breast's degree of emptiness,
ie the emptier the breast, the faster the rate of milk synthesis in the
interval to the next feed. So it is *milk removal* that drives supply after
the initial turning-on of lactation by the endocrine system. The autocrine
system works via an inhibitor peptide in the milk itself that is removed
when the milk is removed, and therefore allows the breast to go into a
higher synthesis rate. Milk left behind means inhibitor left behind too,
and this reduces synthesis rate. A good system to prevent us 'blowing up
and bursting' from producing milk at a faster-than-needed rate! And less
wasteful of raw products needed to make milk as well - ain't Nature clever!?

See Lactnet archives for more details when we discussed this earlier, or
Peter Hartmann's studies - a couple of good summaries of his, and his
students' work are in Journal of Human Lactation:

Daly SEJ & Hartmann PE, 1995, Infant Demand and Milk Supply. Part 1: Infant
Demand and Milk Production in Lactating Women,  J Hum Lact 11(1): 21-26

Daly SEJ & Hartmann PE, 1995, Infant Demand and Milk Supply. Part 2: The
Short-Term Control of Milk Synthesis in Lactating Women,  J Hum Lact 11(1):
27-37

The baby is truly  expert by now, and the pump's
>imitation, second-rate  'sucking action'  just cannot compete with it.

You are right here - the pump may not drain the breast as well as a
well-attached baby, so that the breast may not obtain the same degree of
emptiness after the 'feed'. On the other hand, a baby will not usually take
all the milk available - he will stop when he has had enough - but a mother
may express for longer and empty the breast more than the baby would have.
This latter situation seems to be the case with the mums of NICU babies
discussed recently who had gallons more milk than the baby could take.

When
>lactation is linked with prolactin, the pump usually does okay - but as
>time goes on, many mothers notice they don't get as much at each session.
>It does not mean their supply is going down - though they think it is. It
>only means their breasts respond to the baby rather than a plastic thing.

I disagree here - I believe that their supply *is* going down, because the
breast is getting the message that less milk is needed, because more is
left behind at the end of each 'feed'. It may be true that the mother lets
down more efficiently with the baby, so he gets more, but if this is the
case, ultimately the smaller amount got with the pump results in lower
synthesis rates due to less efficient emptying.

One thing I find interesting is that mothers think that as baby gets
bigger, that he or she needs more milk, and they try to express more per
feed. They may then get quite discouraged if they cannot. In fact, between
1 and 6 months when studies were done by Peter Hartmann and his students,
the baby did *not* increase his overall intake while being exclusively
breastfed. This has also been discussed previously on Lactnet. I think the
paper that this came from was:

Cox D, Owens RA & Hartmann PE, 1996, Blood and milk prolactin and the rate
of milk synthesis in women,  Exper Physiol 81: 1007-1020

I heard Peter talk about this study at a NMAA conference, and this constant
milk intake was not the focus of study (it was the levels of prolactin over
time, and as Heather mentioned, these fall quite quickly after the initial
weeks). I just found it interesting in light of 'growth spurts' or
'appetite increases' that we have always assumed meant that the baby was
needing to increase his overall intake. It seems these may just be
temporary increases in milk intake, and then the baby returns to the
previous level. Of course, *sustained* increase in demand does in fact
increase the supply.

******************************************************************
Joy Anderson B.Sc. Dip.Ed. Grad.Dip.Med.Tech. IBCLC
Nursing Mothers' Association of Australia Breastfeeding Counsellor
Perth, Western Australia.   mailto:[log in to unmask]
******************************************************************

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