Showing Revision 1 created 09/30/2020 by lauren mcalpine .

1. Title:
   The surprising effects of pregnancy
2. 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.

3. 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.