>We understand that oxytocin is responsible for MER and that oxytocin can
>be released
>without suckling (as evidenced by spontaneous MER's w/out a baby at the
>breast).

Yes, higher centres (brain) can do this - thinking about baby, etc. Also,
pressure from full breasts tends to trigger MER more easily.

>We also understand that prolactin is responsible for milk production and
>that prolactin
>is only released in response to the baby's suckling at the breast
>(Lawrence, page71).

Prolactin turns on the whole system after the birth (after withdrawal of
progesterone from placenta delivery), even without suckling (which is why
mothers of stillborn babies still get milk), but suckling is needed to
maintain production. In fact prolactin is present during pregnancy but is
inhibited by the progesterone put out by the placenta. This means that
lactation can be initiated after delivery no matter at what stage of
gestation (after a certain initial period, of course). So prem babies will
have a milk supply just as term babies do.

>Furthermore, it has been stated that the majority of milk is produced
>*during* a
>feeding, which would follow if the prolactin is released during suckling
>and is
>necessary for milk production.
>So, the question is...why do women become full between feedings (or
>over-full if a
>feeding is skipped)?  If there is no baby at the breast, there is no
>release of
>prolactin and, therefore, no production of milk.  Where is that milk
>coming from?

I believe this first statement is no longer thought to be true. It seems
that milk is produced all the time, and the emptier the breast, the faster
the rate of milk synthesis. This is controlled by an inhibitor in the milk
itself, which, if allowed to accumulate (breasts left full), suppresses
milk synthesis rate. When breasts are drained by baby (or expressing), milk
synthesis rate increases. This is the autocrine control of milk production,
and basically takes over from the endocrine system (prolactin) after only a
few weeks into lactation. Each breast is controlled independently this way,
to ensure 'supply' equals 'demand'. For a full explanation of how milk
production is controlled, see Peter Hartmann's studies - two papers in JHL:

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


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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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