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Summary Early Development: Chances & Risks
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Lecture 0 - Nature vs. Nurture• Watson thought regardless of DNA he could make/shape children in whatever way he wants
• Example of behaviorism => All is nurture
• Environment = supreme force in child development
• e.g. Bees: with same DNA but other kind of nutrition you get a di erent phenotype (either a
worker bee or a queen)
• Nowadays we look at how environment in uences expression
of our biology
• E.g. range of reaction of reaction: biology gives a range of
developmental possibilities
• Biology also shapes environment
• E.g. child with down syndrome/di cult temperament —>
parents way more overprotective
• Programming = how expression of our biology is shaped
by the environment
• Might be evolutionary adaptive
Critical and sensitive periods
• Critical period: environment only has an impact during a particular window; e ects are
irreversible (e.g. baby gees following mother, kittens that cannot see with eye that wasn’t open
in rst 3 months of their live)
• Sensitive period: environment shapes a given trait or behavior to a larger extent than in other
periods or stages (e.g. early development in children)
Early development as sensitive period
• Developmental plasticity: capacity to adapt to di erent environments (greatest in rst 1000 days)
• Adapting to the environment makes infants both versatile and vulnerable —> chances & risks
• First 1000 days:
• risks with lifelong consequences for health and wellbeing,
• chances to ‘get things right’ and to boost children's development
• The DOHaD hypothesis: Exposure to certain
environmental in uences during critical or sensitive
periods of development may have signi cant
consequences on an individual’s short and long-term
health
• Intervening early is crucial !!! (Hanson & Gluckman)
• Adoption studies: compare characteristics of adopted
children with those of both their adoptive and biological
parents
• Twin studies: compare the similarities between identical
and fraternal twins reared together or apart
• Identical twins IQ scores look similar even when they are
raised apart —> Nature ?
• IQ scores of child similar to foster parents —> Nurture ?
Chorionic arrangements
• Dichorionic twins: separate placentas & separate fetal circulations, identical or fraternal twins
• Monochorionic twins: one placenta & one fetal circulation, only identical twins
• Greater concordance for MC identical twins than for DC identical twins on: IQ scores, Personality
scores, Schizophrenia, Physiological measures
Summary
• Our biology and the environment interact, shaping our development.
• The rst 1000 days play an important role in development.
• Probable that twin studies underestimated the in uence of prenatal
environment.
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, Lecture 1 - Prenatal development
• Sensitive period: window for the environment to shape fetal development (chances & risks)
• Teratogens: agents that cause deviations during prenatal development (teratology or
developmental toxicity)
• Can cause structural malformations, but also manifestations such as growth retardation and
delays in mental development
• Thalidomide: anti-emetic drug to treat morning sickness (in the
past - end 1956-1962)
• >10.000 children born with severe malformations to the limbs
(phocomelia)
• Around 40% of them died around birth
• Still used today for cancer treatment
• Led to the development of greater drug regulation, especially
during pregnancy, and monitoring in many countries
• Still relevant today: e.g. in discussions around Covid-19 vaccines
for pregnant women
• Animal studies provide experimental evidence: the case of prenatal
diet (e.g. rat studies)
• What is most important prenatal or postnatal diet?
• Mouses that are 3weeks pregnant normal vs. fat diet
• Poor diet in pregnancy + poor diet after —> most determinental
• Diet during pregnancy most important
• Reason => Match-Mismatch model (prepared for less nutrients/food —> experience dat
foods)
Examples of the Match-Mismatch model
• Match-mismatch model: evolutionary model that explains how a developing fetus adapts in
anticipation of the postnatal environment, as a result of cues experienced prenatally
• Thus o spring exposed to a poor diet / less food in utero → adapt to an environment with less
food → to increase the chances for survival and reproduction
• Developmental programming & adaptions to changing environments
• Developmental mismatch: potential cost / risk of developmental programming
• Occurs when environmental cues in early life have limited validity, and thus adaptive responses
fail to correctly predict future environmental conditions
Exposure to poor diet in humans: The dutch Famine study
• Hunger winter —> lack of fuel and food
• > 200.00 people a ected (22.000 people died)
• Daily ratio: 400-800 calories
• Timing of exposure matters (early gestation
especially important)
• Birth weights of babies lower if born in late/mid
gestation, children exposed in early gestation had
normal birth weights (but still more obese,
cardiovascular risks/mortality)
=> Findings aren’t mediated through birth weight
(independent of birth size/weight)
Lessons learned
• Prenatal nutrition can a ect later health without
altering size at birth
• The e ects of famine exposure depend on its timing
• Important to note that an e ect of exposure to prenatal stress, exposure to cold and/or war
cannot be ruled out
• Selection bias might have played a role (e.g. fertility, mortality, selective survival of embryos)
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, Promising interventions
• A daily snack providing additional green leafy vegetables, fruit, and milk before conception and
throughout pregnancy had no overall e ect on birth weigh (Huge dropout)
• Per-protocol (only look at subgroup that did followed the protocol) and subgroup analyses
indicated a possible increase in birth weight if the mother was supplemented >3mo before
conception and was not underweight
Pregnant woman’s distress
• No need to know all the tables/ Concentrate on main ndings (e.g. conclusion and implication
parts of the review) —> abstract & conclusion
• Research focuses mostly on prenatal stress and anxiety (to lesser extend on depression),
working mechanism a ecting pregnancy di erent for stress vs. depression
How to study distress?
1) Ask mothers using questionnaires
• The estimation of the percentage of woman experiencing prenatal stress varies widely
• 8–12% of pregnant women meet criteria for a mental disorder (anxiety, mood disorder)
• Underestimation? In a large-scale community study using self-reports about 30% of pregnant
women reported some type of stress
• A ects children's temperament (negative a ectivity, crying), behavioral problems
(externalizing, internalizing, social problems, psychiatric problems), cognitive outcomes (WM,
IQ)
• Limitations: often asked long time afterwords, reasons unclear,
2) Investigate exposure to life events during pregnancy
• Includes life events such as death of a relative accidents or life-threatening illnesses of a relative
• Possibility to tease apart timing to some extend (timing of life events, objective vs. subjective
stress -> e.g. closeness of ill relative allows teasing apart)
• A ects children showing ADHD symptoms and behavioral problems (internalizing,
externalizing, psychiatric problems)
• e.g. asked through teacher report to get more objective view
3) Investigate exposure to natural distress during pregnancy (e.g. 9/11)
• Often happen very unexpectedly -> can investigate timing
• Can objectively measure e.g. how many days someone was without electricity and later ask
how they were feeling during the event
• A ects children's motor development (negatively), Cognitive development (negatively, e.g. IQ
& language development), negative a ectivity
Important to note
• Maternal stress and anxiety more impact than depression
• Both sexes impacted but there are also sex-speci c e ects
• Not all studies nd e ects! Publication bias? Reporter bias?
• Gestational timing seems to matter, but more research needed
• Not all associations are investigated over time and/or persist over time
• No causality can be assumed. What about genes? What about maternal postpartum distress, as
stress often continuous? Parenting quality? Genes?
• Not only brain and behavior, but child health seems to be also impacted
• In rst 12months prenatal anxiety and stress predicted: respiratory illnesses, general illnesses,
skin illnesses, antibiotic use, (not digestive illness)
• Follow up study shows not all associations remain: late pregnancy anxiety and cortisol—>
respirators illness & digestive illness till age 3, more maternal prenatal stress—> antibiotic use
(1y-6y)
Covid-19 crisis
• During covid-19, percentage of mothers scoring above clinical cut-o s doubled for depression
& anxiety
• Women reported increased partner support, but decreased social & healthcare support
• Future generation will need some more attention to help with e ects
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, Literature
Lessons learned from 25 Years of Research into Long term Consequences of Prenatal
Exposure to the Dutch famine 1944–45: The Dutch famine Birth Cohort (Susanne et.al. 2021)
• The consequences of prenatal undernutrition depend on timing during gestation
• Early gestation particularly critical
• Undernutrition a ects structure & function of organs/tissue, behavior and risk of mental physical
& chronic degenerative diseases
Consequences of prenatal undernutrition
• Babies exposed during early gestation: heavier, longer, placenta more e cient, more
atherogenic lipid pro le, disturbed blood coagulation, increased cardiovascular disease, (no
increase in strokes), increased stress induced elevation in blood pressure, increased wear and
tear of the cardiovascular system, increased breast cancer, overall perfusion of brain worse,
Men lower perfusion of anterior and posterior cingulate cortices (=> higher risk for
neurodegenerative diseases)
• Babies exposed during mid-late gestation: lighter, shorter, placenta less e cient, more
prevalent micro-albuminuria & obstructive airways disease (critical period for kidney and lung
development)
Metabolic and cardiovascular outcomes
• Women more obese at age 50
• Reduced glucose tolerance
• Risk of type 2 diabetes
• Higher glucose levels (caused by function changes in pancreatic ß cells & sensitivity to insulin)
• Defective ß-functioning
• Functional changes in liver
• Preference for fatty foods
• Reduced intima media thickness (IMT)
• No di erence in cortisol response to stress or cortisol after dexamethasone suppression and
ACTH1-24 stimulation
• Combination of three or more syndrome components of metabolic syndrome not more often
present
Reproductive and transgenerational outcomes
• No di erences in sexual orientation or gender identity
• Women exposed to famine during gestation more reproductively successful
• Poor nutrition during fetal development + improved nutrition after birth = female phenotype
with greater reproductive success
• Children of mothers that were exposed to famine prenatally -> heavier at birth
• Children of fathers prenatally exposed to famine parentally -> heavier in adult live
• Transgenerational e ects of famine exposure through maternal and paternal line
Other physical health outcomes
• Prenatal famine exposure not associated with Irritable Bowel Syndrome (IBS), but those
exposed to famine in early life more often a ected by IBS
Mental health and quality of life
• Men exposed to famine in early gestation = more symptoms of depression & anxiety
• Exposed Men = lower conscientiousness, Women = higher agreeableness
• No di erence in general perceived stress in daily life
• Rated general health as poorer
Aging
• Decreased physical function in later life in men but not women
• Both genders poorer cognitive function at age 58
• Men exposed in early gestation = intracranial volumes & brain size smaller (reduction ca. 5%)
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