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Prenatal Development
and the Newborn Period
How Children Develop
Chapter 2
Overview
Prenatal
Development
The Birth
Experience
The Newborn
Infant
Prenatal Development
Conception, Developmental
Processes, and
Early Development
Fetal Behavior, Experience,
and Learning
Hazards to Prenatal
Development
Conception
Results from the union of two gametes, the egg and the sperm
Gametes produced through specialized cell division, meiosis:
Each has only half the genetic material of all other normal cells in the
body
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Prenatal Development
1. Ovum (1/175 inch) + Sperm (1/500 inch) = Baby
1. Of 360 million released by male, only 100 reach
ovum.
Sperm live for 48 hours – they swim for 6 hours, they lie in wait.
Prenatal Development
1. Ovum (1/175 inch) + Sperm (1/500 inch) = Baby
1. Of 360 million released by male, only 100 reach
ovum.
Sperm live for 48 hours – they swim for 6 hours, they lie in wait.
Sperm Competition
Sex Differences
Begin at Conception
Approximately 120 to 150 males are conceived for every 100 females
How and why?
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Sex Differences
Begin at Conception
Approximately 120 to 150 males are conceived for every 100 females
How and why?
Y chromosome sperm than X chromosome sperm
Male embryos are rates, and boys are more vulnerable to developmental disorders and illness
Sex Differences
Begin at Conception
The Zygote
The fertilized egg, or zygote, has a full complement of human genetic material, half from each parent
Marks the beginning of the three periods of prenatal development
Germinal: Begins with conception and lasts until the zygote becomes implanted in the uterine wall. Rapid cell division takes place.
The Zygote
Embryonic: Following implantation, major development occurs in all the organs and systems of the body.
Fetal: Continued development of physical structures and rapid growth of the body. Increasing levels of behavior, sensory experience, and learning.
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Periods of
Prenatal Development
Germinal(conception - 2 weeks)
Embryonic(3rd - 8th week)
Fetal(9th week - birth)
The Cells
Four major developmental
processes transform a
zygote into an embryo and then into a fetus
1. Cell division results in the proliferation of cells
2. Cell migration is the movement of cells from their
point of origin to somewhere else in the embryo
3. Cell differentiation transforms the embryo’s
unspecialized stem cells into roughly 350
different types of cells
4. The selective death of certain cells, or
apoptosis, also enables prenatal development
The Cells
Four major developmental
processes transform a
zygote into an embryo and then into a fetus
1. Cell division results in the proliferation of cells
2. Cell migration is the movement of cells from their
point of origin to somewhere else in the embryo
3. Cell differentiation transforms the embryo’s
unspecialized stem cells into roughly 350
different types of cells
4. The selective death of certain cells, or
apoptosis, also enables prenatal development
The Role of Hormones
Hormones play a crucial role in sexual differentiation All human fetuses can develop either male or
female genitalia, depending on the presence or absence of testosterone
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The Role of Hormones
Hormones play a crucial role in sexual differentiation All human fetuses can develop either male or
female genitalia, depending on the presence or absence of testosterone
One of the many ways in which the fetus acts as an instigator of its own development
The Blastocyst
By the 4th day after conception, the
zygote arranges itself into a hollow
sphere of cells with a bulge of cells,
the inner cell mass, on one side
The inner cell mass eventually forms
into the embryo
Protecting the Fetus
The placental membrane is a barrier against
some, but not all toxins and infectious agents
The amniotic sac, a membrane filled with
fluid in which the
fetus floats,
provides a
protective
buffer for
the fetus
The Fetus: An active contributor
to its own development
By 12 weeks after gestation, most of
the movements that will be present at
birth have appeared
Swallowing amniotic fluid promotes the
development of the palate and aids in the
maturation of the digestive system
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The Fetus: An active contributor
to its own development
By 12 weeks after gestation, most of
the movements that will be present at
birth have appeared
Swallowing promotes the
development of the palate and aids in the
maturation of the
Pulling in and expelling small amounts of
help the
become functional
Sensation
The sensory structures are present
relatively early in prenatal development
and play a vital role in fetal development
and learning
The fetus experiences tactile stimulation as
a result of its own activity, and tastes and
smells the amniotic fluid
It responds to sounds from at least the
6th month of gestation
Prenatal visual experience, however, is
negligible
Fetal Learning
At 32 weeks’
gestation, the
fetus decreases
responses to
repeated or
continued
stimulation, a
simple form of
learning called
habituation
Fetal Learning
Newborn infants
have been shown to
recognize rhymes
and stories presented
before birth
Newborns also prefer
smells, tastes, and
sound patterns that
are familiar because
of prenatal exposure
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Miscarriage
By far the most common misfortune in
prenatal development is spontaneous
abortion (miscarriage)
Miscarriage
By far the most common misfortune in
prenatal development is spontaneous
abortion (miscarriage)
Around or more of conceptions result
in very early miscarriages, and about
of pregnancies of which women are
aware are miscarried
The majority of embryos that miscarry
very early have severe defects
Teratogens (Greek: teras – monstrosity):
Environmental agents that
have the potential to cause
harm during prenatal
development
Timing is a crucial factor
in the severity of the
effects of potentially
harmful agents
Many agents cause
damage only if
exposure occurs during
a sensitive period in
development
Sensitive Periods
p. 60
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Teratogens
What effects impact of a teratogen?
Amount and length of exposure.
Genetic make-up of mother and baby.
Multiple negative factors (poor nutrition,
no medicine).
Age of organism at time of exposure.
Teratogens
What effects impact of a teratogen?
Amount and length of exposure.
Genetic make-up of mother and baby.
Multiple negative factors (poor nutrition,
no medicine).
Age of organism at time of exposure.
Teratogens include legal as well as
illegal substances...
Some Environmental Hazards
to Fetus or Newborn
p. 62
Any drug that mother takes affects fetus.
Good example is the anti-naseau thalidomide.
But, many pregnant women take unprescribed drugs:
Aspirin: linked to low birth weight (LBW), infant
death, poor motor development…and on and on.
Caffeine (heavy use): linked to LBW, miscarriage,
irritable and vomiting newborns.
Prescription and
non-prescription drugs
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Teratogens
Maternal alcoholism can lead to fetal alcohol syndrome
(FAS), which is associated with mental retardation, facial
deformity, and other problems
FAS is the leading cause of mental retardation in western civilization.
Teratogens
Cigarette smoking during
pregnancy is linked to
retarded growth and low
birth weight
Cigarette smoking has also
been linked to SIDS (sudden
infant death syndrome),
although the ultimate causes
of SIDS are still unknown
Parents can reduce the risk by not smoking, putting babies to
sleep on their backs, using firm mattresses and no pillows,
not wrapping infants in many blankets
Teratogens
• cocaine babies born yearly
Babies born to cocaine users
Physical: Eye, bone, genital, kidney, heart deformities.
Babies born to users of heroin & methadone:
Physical: LBW, physical defects, breathing problems, drug
addicted
Psychological: Less attentive, motor development slowed.
Marijuana – less is known and mixed findings.
Evidence of disturbed sleep, startles, tremors.
Maternal Factors
The age, nutrition, disease, and stress-level of the mother have an impact on prenatal development
Infants born to girls 15 years or younger are three to four times more likely to die before their first birthday than are those whose mothers are in their 20s
Inadequate nutrients or vitamins such as folic acid can have dramatic consequences (e.g., growth of the fetal brain)
born
undernourished yearly in US. Only
72% of impoverished
mothers given extra food.
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Nutrient
Folic acid
Vitamin D
Iron
Calcium
Phosphorus
Pyridoxine
Thiamin
Zinc
Riboflavin
Protein
Iodine
Vitamin C
Energy
Magnesium
Niacin
Vitamin B-12
Vitamin A
180 mcg
5 mg
15 mg
800 mg
1.6 mg
1.1 mg
12 mg
1.3 mg
50 g
150 mcg
60 mg
2200 kcal
280 mg
15 mg
2.0mcg
800mg
Pregnant
400 mcg
10mg
30 mg
1200 mg
1200 mg
2.2 mg
1.5 mg
15 mg
1.6 mg
60 g
175 mcg
70 mg
2500 kcal
320 mg
17 mg
2.2 mcg
800 mg
Percent
Increase
+122
+100
+100
+50
+50
+38
+36
+25
+23
+20
+17
+17
+14
+14
+13
+10
0
Dietary Sources
Leafy vegetables, liver
Fortified dairy products
Meats, eggs, grains
Dairy products
Meats
Meats, liver, enriched grains
Enriched grains, pork
Meats, seafood, eggs
Meats, liver, enriched grains
Meats, fish, poultry, dairy
Iodized salt, seafood
Citrus fruits, tomatoes
Proteins, fats, carbohydrates
Seafood, legumes, grains
Meats, nuts, legumes
Animal proteins
Dark green, yellow, or orange
fruits and vegetables, liver
Nonpregnant
Source: Data from Reece et al., 1995. From Reece, E.A., Hobbins, J.C., Mahoney, M.J., and Petrie, R.H. (1995) HANDBOOK OF MEDICINE OF THE FETUS AND THE MOTHER. Copyright © 1995. Used by permission of Lippincott Williams & Wilkins (http://lww.com)
Table 4.5
Nutritional Need Difference Between Non-pregnant and Pregnant Women (24 Years Old)
The Birth Experience
The Birth Experience
Approximately 38 weeks after conception, contractions
of the uterine muscles begin, initiating the birth of the
baby
Research on the birth process has revealed that many
aspects of the birth
experience, including
squeezing in the birth
canal, have adaptive
value and increase the
likelihood of survival for
the newborn
Psychological Stress
High anxiety linked to miscarriage, LBW, respiratory illness
Why?
• Under stress blood rushes to heart, brain, muscles - away
from uterus.
• Anxious women more likely to smoke, drink, eat poorly.
Reduced by partner, friends: with help had complicated
pregnancy, without help had complication.
Maternal Age:
• Birth in 30s are increasing (best is 16-34).
• But, less problems if mother is healthy.
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Assessing the Newborn’s Condition – Apgar Scale
Rating from 0-2 on five ratings
Score of 7+ is good, 4-6 help needed, 3- is bad.
The Newborn’s
Appearance
Average = 20 inches
long, 7½ pounds.
Big head – they learn
quickly but are
immobile.
Interacting with the
Environment
State: The infant’s
level of arousal and
engagement in the
environment
Ranges from deep
sleep to intense activity
Is an important
influence in the
newborn’s exploration
of the world
Six States of Arousal
1. Active sleep
2. Quiet sleep
3. Crying
4. Active awake
5. Alert awake
6. Drowsing
Newborn States
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Sleep
Newborns sleep twice as much as young adults
The pattern of two different sleep states changes dramatically
REM (rapid eye movement) sleep:An active sleep state associated with dreaming in adults
Non-REM sleep: A quiet or deep sleep state characterized
Sleep
REM sleep constitutes fully 50% of a newborn’s total
sleep time and declines rapidly to only 20% by 3 or
4 years of age...
Why?
Infant Mortality Worldwide (2002)
p. 75
Infant Mortality
Death during the first year after birth
(infant mortality) has become a relatively rare
event in the Western industrialized world
However, rates in the United States are the 23rd
highest in the world...
African-American infants are more than twice as
likely to die before their first birthday as Euro-
American babies
Why?
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Low Birth Weight Infants
Infants weighing less than 5.5 pounds
(2,500 grams) are considered to be of
low birth weight (LBW)
LBW infants born at or before 35 weeks after
conception are described as premature
Other LBW infants are referred to as small for
gestation age (SGA) when their birth weight is
substantially less than the norm for their
gestational age
LBW Infants
As a group, LBW babies experience
more medical complications, have
more developmental difficulties, and
present special challenges for parents
However, the majority of LBW
babies turn out quite well
They need extensive parent
contact and more touch
Smallest Newborn to Survive
Born in 1989 after just 27 weeks of gestation,
Madeline weighed a mere 9.9 ounces. She
recently entered high school as an honor
student and enjoys playing her violin and rollerblading.
Risk Factors
Tend to occur
together in the world
A negative outcome
is more likely when
there are multiple
risk factors
Despite multiple risk
factors, however,
some individuals do
well