WEBVTT

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In this section
we're going to be

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thinking about the
impact of stress

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on the developing foetus.

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The prevalence of
common mental health

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problems in the
antenatal period is high.

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Antenatal stress is
common, with as many as 20%

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of women experiencing symptoms
of anxiety in pregnancy.

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Both anxiety and
depression in pregnancy

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are associated with
postnatal depression.

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Many women also experience
other problems in pregnancy

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that are strongly associated
with anxiety and depression.

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For example, around 30%
of domestic abuse starts

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during pregnancy and
around 9% of women

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are being abused
during pregnancy

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or after giving birth.

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Around 1% of
pregnancies in the UK

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involve a drug-dependent mother.

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And such drug
dependency co-occurs

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with a range of other problems,
including psychiatric disorder

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and particularly
disorders related

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to emotional regulation.

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Adverse prenatal
mental health has

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been shown to be associated
with a wide range of compromised

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outcomes for the baby,
both in the short term,

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such as immediately
following the birth,

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and in the longer term through
to adolescence and adulthood.

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We've known for a very
long time, for example,

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that very severe stress
can have an impact

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on physical aspects of the
unborn baby's development.

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For example, research shows
that in the first trimester,

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the death of an older
child was associated

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with an increase in
congenital malformations,

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while less severe
forms of stress

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were associated with low
birth weight and reduced

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gestational age and
an altered sex ratio

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with fewer males
to females being

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born than in an
unstressed population.

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However, more recent
studies have also

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begun to identify an impact
on a range of aspects

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of the child's
neurodevelopmental and

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socioemotional functioning.

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For example, a number of studies
have identified an impact

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of maternal stress
in pregnancy on

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the neurodevelopmental
functioning of newborn babies,

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including an increase in
fearfulness and difficult

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temperament, sleep problems and
lower cognitive performance.

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Studies that have
examined the association

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between prenatal stress and
neurodevelopmental outcomes

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in children aged 3 to 16
years show an increased risk

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of child emotional
problems, especially anxiety

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and depression, and symptoms
of attention deficit

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and hyperactivity disorder
and conduct disorder.

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Other studies have
shown a reduction

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in cognitive
performance associated

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with prenatal stress.

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So what might the
mechanisms for this be?

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Although we don't
currently fully understand

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the mechanisms that may
underlie foetal programming

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by prenatal stress in humans,
a number of potential pathways

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have been identified.

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One early suggestion was
a decrease in blood flow

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to the foetus as a
result of the increased

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stimulation by cortisol
of the mother's

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sympathetic nervous system.

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This in turn was thought to
cause increased constriction

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of her blood vessels, which
reduced uteroplacental blood

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and reduced oxygen and
calorie intake for the foetus.

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However, more
recent research has

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suggested that a more
likely mechanism that

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has been identified
in animal models

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only involves the
foetus being overexposed

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to cortisol as a result
of maternal cortisol

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crossing the placenta.

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A number of studies have
shown that maternal stress can

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influence the
transfer of cortisol

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across the placenta as a result
of changes to the barrier

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enzyme which converts cortisol
to the inactive cortisone.

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High levels of cortisol can
be toxic for the foetal brain

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and can adversely affect a
number of areas of both foetal

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and child brain,
including the HPA axis,

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which is responsible for
setting the stress thermostat

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and results in these
children experiencing

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higher levels of stress
throughout childhood

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into adulthood.

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Increased serotonin is
another possible mediator

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of prenatal stress on the
neurocognitive and behavioural

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development of the baby.

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In humans, stress during
pregnancy caused by violence

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from the partner
has also been shown

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to cause epigenetic changes
in the DNA in the blood

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of their adolescent children.

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In the next video, I talk
to Vivette Glover, who

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is Professor of Perinatal
Psychobiology at Imperial

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College London and
we explore some

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of these issues in more detail.

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The supporting
article and the video

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provides you with
the opportunity

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to learn more about the
impact of stress in pregnancy.

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Please also share your
thoughts about this section

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of the course in
the discussions.

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