How Mother's Milk Is Made
Linda J. Smith, BSE, FACCE, IBCLC
Dayton, Ohio, USA
From: LEAVEN, Vol. 37 No. 3, June-July 2001, p. 54-55
"Not enough milk"
is the most common reason for supplementing or discontinuing breastfeeding.
Sometimes this is real; other times it is imagined. The progress in
understanding milk synthesis comes partly from dairy physiologists (who
have a financial interest in knowing exactly how to have cows produce
plenty of milk) and partly from those helping women breastfeed.
Before the 1940s, everyone
thought most of the milk was made during the let-down reflex, because
it flows faster during let-down. (This included dairy scientists as
well as breastfeeding advocates.)
In 1944, Peterson showed
that milk secretion was continuous but let-down was a different and
separate process. Letdown (or MER-milk ejection reflex) squeezes out
milk that is already made and stored in the alveolar lumen (small ducts
into which milk from the alveoli is ejected). Milk isn't made any faster
during MER. It just flows faster.
Since the 1990s, Peter Hartmann's
research in Australia with breastfeeding women has found (actually "is
finding" because this research is ongoing) that the rate of milk
synthesis - how fast the secretory cells make milk - is related to the
degree of emptiness (or fullness) of the breast. This is called autocrine
(or local) control. As the alveolar lumen fills, compounds in the retained
milk itself (Feedback Inhibitor of Lactation or FIL, peptides, fatty
acids, and possibly other components) signal the secretary cells to
slow down milk synthesis. The emptier the breast is, the faster it tries
to refill - similar to an automatic icemaker. Hartmann says the rate
of milk synthesis in women ranges from 11 to 58 ml/hour/breast, or about
1/3 of an ounce to 2 ounces per breast per hour. Emptier breasts make
milk faster than fuller ones. When milk is regularly and thoroughly
removed from the breast, milk synthesis is unrestricted.
Hartmann's research has
documented what we in La Leche League have known for a long time--that
milk supply is regulated by baby's needs. A baby rarely empties all
of the available milk from his mother's breasts. In 1993, Hartmann found
that babies remove an average of 76 percent of the available milk from
their mother's breasts in a 24-hour period. This allows a baby to have
short-term control of his mother's milk production.
I explain this using what
I call the "80:20 concept." The 80 percent is the usual amount
of milk taken by baby each day. The 20 percent is the residual amount
of milk that remains in mother's breasts. If more than 80 percent of
the milk is removed, supply increases to maintain the 80-20 ratio.
If less than 80 percent is removed, supply decreases to maintain
the 80-20 ratio. Even though this is an over-simplification of a very
complex process, the core principle has held steady as new research
emerges.
Research shows that the
mother's diet, her fluid intake, and other factors have little influence
on milk production. If the "milk removal" piece of the puzzle
is in place, mothers make plenty of good milk regardless of dietary
practices. If the "milk removal" part isn't there, nothing
else can make up the difference.
The significant inhibiting
(risk) factors to a full milk supply appear to be (1) breast surgery;
(2) retained placenta; (3) Sheehan's syndrome or pituitary shock; (4)
hormonal contraception; and (5) insufficient glandular tissue. If none
of those are factors for a mother, it's exceedingly rare that she won't
make plenty of milk. Rare situations do exist, however.
In my practice, there are
two common reasons for "not enough milk": (1) the baby isn't
at breast enough minutes per day, nursing sessions are ended before
the baby lets go, or feeding intervals are stretched out too far between,
or something else is given to the baby to "tide him over,"
or (2) the baby is not effectively transferring milk: either because
of shallow attachment at the breast or a sucking problem.
The research shows that
preventing and treating engorgement quickly is critical. Whenever possible,
all feedings should be directly at the breast following baby's cues.
Mothers should allow baby to finish the first breast first, watch for
baby to signal when he is finished by self-detaching, and then offer
the second breast. Babies need to breastfeed 8-12 times per day until
the milk supply is established. Most babies will breastfeed a total
of at least 140 minutes per day, averaging 10-30 minutes per nursing
session. Mothers can be encouraged to use breastfeeding for both nourishment
and nurture.
My plea to all: Look at
the baby carefully. I don't hesitate to recommend pumps as tools because
I see so many young babies with temporary poor suck responses. The poor
suck leaves milk in the breast, which compromises milk supply, resulting
in a hungry disorganized baby and no milk. With a good pumping routine,
the mother has plenty of her own milk to work with while we figure out
how to help the baby feed better at the breast. Supply is usually the
easiest part to fix. Remember, it's still supply and demand, or "use
it or lose it."
Linda J. Smith, BSE,
FACCE, IBCLC is an internationally known author, teacher, lecturer,
and proud grandmother. She has been an LLL Leader for almost 27 years
in nine cities and two countries. Linda is a lactation consultant in
private practice in Dayton, Ohio, USA. She is a founder of IBLCE, founder
and past board member of ILCA, and currently sits on the United States
Breastfeeding Committee representing the Coalition for Improving Maternity
Services (CIMS). Linda and her husband, Dennis, own and operate the
Bright Future Lactation Resource Center (www.bflrc.com).
References
Cox, D.B., Owens, R.A.,
and Hartmann, P.E. Blood and milk prolactin and the rate of milk synthesis
in women. Exp Physiol 1996; 81 (6): 1007-20.
Cox, D.B., Owens, R.A.,
and Hartmann, P.E. Studies on human lactation: the development of the
computerized breast measurement system (1998). http://mammary.nih.gov/reviews/lactation/Hartmann001/index.html
Cregan, M.D. and Hartmann, P.E. Computerized breast measurement from
conception to weaning: clinical implications. J Hum Lact 1999;
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Daly, S.E.J., Kent, J.C.,
Owens, R.A., and Hartmann, P.E. Frequency and degree of milk removal
and the shortterm control of human milk synthesis. Exp Physiol
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Daly, S.E.J. and Hartmann,
P.E. Infant demand and milk supply. Part 1: infant demand and milk supply
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Daly, S.E.J. and Hartmann,
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Daly, S.E.J., Owens, R.A.,
and Hartmann, P.E. The short-term synthesis and infant-regulated removal
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Daly, S.E.J., Kent, J.C.,
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Exp Physiol 1992; 77(1): 79-87.
De Coopman, J. Breastfeeding
after pituitary resection: support for a theory of autocrine control
of milk supply? J Hum Lact 1993; 9(1): 35-40.
Peaker, M. and Wilde, C.J.
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Peterson, W.E. Lactation. Physiol Rev 1944; 24: 340-71.
Riordan, J. and Auerbach
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Last updated Friday, October 13, 2006 by njb.
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