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Title:
The surprising effects of pregnancy
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Description:
View full lesson: https://ed.ted.com/lessons/the-surprising-effects-of-pregnancy
Muscles and joints shift and jostle. The heart’s pounding rhythm speeds up. Blood roars through arteries and veins. Over the course of a pregnancy, every organ in the body changes. Initiated by a range of hormones, these changes begin as soon as a pregnancy begins. Explore what we know— and don’t know— about pregnancy's effects on the body and brain.
Lesson by TED-Ed, directed by Roxane Campoy and Charlotte Cambon.
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Speaker:
TED-Ed
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Muscles and joints shift and jostle.
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The heart’s pounding rhythm speeds up.
Blood roars through arteries and veins.
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Over the course of a pregnancy,
every organ in the body changes.
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Ignited by a range of hormones,
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these changes begin
as soon as pregnancy begins.
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Just days after fertilization, the embryo
implants in the lining of the uterus.
¶
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Because its DNA doesn’t exactly match
the mother’s,
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the immune system should theoretically
recognize it as an invader,
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attack, and destroy it, like it would
bacteria or other harmful microbes.
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That’s the challenge:
the mother’s immune system
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needs to protect both her and the fetus,
but can’t act as it usually does.
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What happens is not as simple
as decreasing the immune response.
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Instead, it’s a complex interaction
we’re just beginning to understand,
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involving many different types
of immune cells—
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some of which seem to protect the fetus
from attack by other immune cells.
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The body also creates an antibacterial
plug made of mucus on the cervix,
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which keeps germs away
and stays sealed until labor.
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As a pregnancy progresses,
¶
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the uterus expands upward and outward
with the growing fetus.
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To make room, hormones
called progesterone and relaxin
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signal muscles to loosen.
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The muscles that propel food and waste
through the digestive tract also loosen,
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which makes them sluggish,
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causing constipation as passage
through the tract slows down.
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Loosened muscles
at the top of the stomach
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might allow acid to escape
into the esophagus and throat,
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causing heartburn and reflux.
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These changes can worsen morning sickness,
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which is caused in part by hormone HCG—
and can also happen at other times of day.
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As the uterus grows,
it pushes on the diaphragm,
¶
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the muscle that expands and contracts
the chest with each breath.
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This limits the diaphragm’s range.
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To compensate, the hormone progesterone
acts as a respiratory stimulant,
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making the pregnant woman breathe
faster so both she and the baby
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can both get enough oxygen
with less lung capacity.
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This all may leave the pregnant woman
feeling short of breath.
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Meanwhile, the kidneys
make more erythropoietin,
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a hormone that increases
red blood cell production.
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The kidneys also keep extra water and salt
rather than filtering it out into urine
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to build up the volume of the blood.
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A pregnant woman’s blood volume
increases by 50% or more.
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But it’s also a bit diluted,
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because it only has 25%
more red blood cells.
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Usually, the body makes blood cells
using iron from our food.
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But during pregnancy, the fetus
is also building its own blood supply
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from nutrients in the mother’s food—
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leaving less iron and other nutrients
for the mother.
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The heart has to work extra hard
to pump all this blood
¶
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through the body and placenta.
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A pregnant woman’s heart rate increases,
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but we don’t fully understand how blood
pressure changes in a healthy pregnancy—
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an important area of research,
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because some of the most serious
complications
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are related to the heart
and blood pressure.
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The expanding uterus may press on veins—
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causing fluid buildup
in the legs and feet.
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If it presses on a large vein
called the inferior vena cava,
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it might interfere with blood
returning to the heart,
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causing a dizzying drop in blood pressure
after standing for too long.
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Some of these changes start
to reverse even before birth.
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Shortly before delivery,
the fetus drops down,
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decreasing the pressure on the diaphragm
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and allowing the pregnant woman
to take deeper breaths.
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During labor and birth,
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much of the extra fluid in the body
is lost when the water breaks.
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The uterus shrinks back down
in the weeks after birth.
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Like the rest of the body,
pregnancy affects the brain—
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but its effects here are some
of the least understood.
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Recent studies show differences
in brain scans
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after pregnancy and early parenting,
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and suggest that these changes
are adaptive.
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That means they could help
with parenting skills,
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such as an increased ability to read
facial cues since babies can’t talk.
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The lack of information about pregnancy’s
effects on the brain
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highlights a general truth: historically,
almost all the research around pregnancy
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has focused on the fetus,
rather than pregnant women.
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Experiences of pregnancy vary widely,
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both within the range
of healthy pregnancies
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and due to complicating health conditions—
new research will help us understand why,
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and develop effective treatments
where necessary.
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In the meantime,
every pregnancy is different,
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and it’s important to consult a doctor
with any specific questions.
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Today, we’re turning an exciting corner,
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as more research is devoted
to the astounding biology of pregnancy.