Transcript Lactation - Washington State University

Lactation
Mammaries are why we call her
Mama
Mechanism of afterpains
• The mother is encouraged to allow the baby to suckle soon
after birth, even though milk production is inhibited by the
presence of residual progesterone in the mother’s body – the
level of P will gradually diminish because the source, the
placenta, is now gone. Milk may not be available for 2 days or
more…
• Colostrum is already available in the breasts and when the
baby suckles, it provides valuable antibodies, some nutrients,
and fluid.
• The stimulation of the nipples in suckling acts on nerve endings
that cause oxytocin to be delivered from the mother’s posterior
pituitary. This also causes contractions of the uterus called
afterpains that are good pains, because they cause the uterine
muscle to contract, which reduces bleeding and helps the
uterus to return to normal size (involution: a process that takes
4-6 weeks) sooner than it otherwise will.
Factors involved in milk production and milk
letdown
• In nonpregnant women (and males), prolactin secretion
is tonically inhibited by dopamine (d2 receptors). This
inhibition is relieved by the hypothalamus during
pregnancy.
• During pregnancy, estrogen, progesterone, prolactin and
placental lactogen prepare breasts for lactation, but
progesterone also inhibits actual milk secretion.
• After loss of the placenta, oxytocin is released from the
post. pituitary reflexively with suckling – it causes milk
letdown. This is a conditionable reflex.
• Suckling maintains prolactin secretion- prolactin supports
milk production and also may promote maternal
behavior.
Ideally, the postpartum period is for bonding
• Bonding is a part of human nature, and does not
require breastfeeding, but it certainly is facilitated by
this mode of continuing the mother-child
interdependency.
• The hormonal regulation of brain changes that
promote care of the young is most closely associated
with prolactin – in both sexes. The mother who
breastfeeds will have prolactin released in response to
nipple stimulation. In the case of males, those fish,
birds and mammals in which the male takes part in
care of the young, all show increases in prolactin
during the care period. Studies of tamarins and
marmosets, among the primates, have shown that
prolactin levels rise before the birth of the young, and
so the males are “primed” for their roles.
What is in human milk
•
•
•
•
•
•
•
•
•
•
Lactose 7.3 g/dl
Oligosaccharides: 1.2 g/dl
Protein: 0.8 g/dl
Triacyglycerols: 4%
Phospholipids: 0.04%
Na+: 5 mEq/l
K+: 15 mEq/l
Cl-: 15 mEq/l
Ca++: 16.0 mEq/l
Mg++: 2.8 mEq/l
• The milks of various
mammalian species are
quite different from each
other. For example, the
carbohydrate content of
bovine milk is lower than
that of human milk and
the protein and mineral
contents are higher.
These differences affect
its digestibility by human
babies (remember, cows
have 3 stomachs to our
1).
The sequence of delivery
• When women examine their own milk,
especially the first milk that is delivered in
a feeding, they are negatively impressed
by its weak appearance:
• Foremilk is low-fat, with proteins and
carbohydrates.
• Hindmilk is fattier, creamier, and provides
a satisfying completion of the nursing
experience.
the hypothalamus knows best
SUCKLING
Hypothalamus
↓dopamine secretion
Ant pituitary lactotrophs
↓ GnRF secretion
Ant Pituitary luteotrophs
↑ prolactin secretion
↑ oxytocin secretion
Milk letdown
↓LH secretion
Milk production maintained
Ovary
Follicle maturation inhibited
Multifunctional oxytocin
• Labor contractions
• Mother-infant bonding in minutes-hours
after birth
• Regression of uterus after delivery
• Milk letdown (more bonding?)
• Orgasm contractions male/female
• Male-female bonding (?)
The contraceptive effect of breast-feeding:
breast-feed, don’t breed
• Contraceptive effect of lactation is diminished by
– Loss of nighttime feedings
– Diet supplementation
Bottle-feeding: cycling begins 8 weeks after delivery;
ovulation begins 11 weeks after delivery
Breast-feeding: cycling begins at about 33 weeks;
ovulation at 36 weeks – no woman ovulates who
breast-feeds six or more times daily for a total of 60
min, and who does not supplement child’s diet with
formula (‘daddy’s milk’).
Superior properties of breast milk
• No potentially unclean containers or formula water
needed – so less diarrheal disease
• Inexpensive
• Prewarmed to correct temperature
• Promotes mother-child bonding
• Milk letdown helps uterus return to non-pregnant size
(oxytocin effect)
• Transfers maternal antibodies and growth factors
• Iron is complexed with lactoferrin, making it more
available than it would be as an inorganic salt
• Less likely to provoke food allergies
• Direct relationship between duration of breast-feeding
and child’s IQ – 6 months of breast feeding = 8 IQ points.
Breastfeeding transfers immunity: the immunoglobulins.
Secretory IgA is the dominant antibody in milk
•
•
•
•
Breastfeeding benefits for the baby:
1. Ideal nutrient mixture
2. bonding, body-contact time with mother
3. Passive immunity, both antibodies and
white blood cells are transferred, resulting
in fewer childhood illnesses
• 4. Fewer food allergies
• 5. Immune system development promoted
• 6. Brain development controlled studies
indicate a boost of 8 IQ points for
breastfeeding 6 months
A Downside - Lactation can channel environmental
toxins to the infant
• Many drugs and toxins that circulate in maternal
bloodstream may also be secreted in milk.
• Fat-soluble toxins that have accumulated in
maternal fat may be released into the blood by
fat breakdown during lactation – these may then
be transferred to the nursing infant.