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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