Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Chapter 3
Prenatal Development
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Prenatal Development: Truth or Fiction?

Newly fertilized egg cells survive without any nourishment from
the mother for more than a week.

Your heart started beating when you were only one-fourth of an
inch and weighed a fraction of an ounce.
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Prenatal Development: Truth or Fiction?
 If it were not for the secretion of male sex hormones a few weeks
after conception, we would all develop external sex organs that
look like those of females.
 Fetuses suck their thumbs and hiccough, sometimes
for hours on end.
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Prenatal Development: Truth or Fiction?
 It is harmless to the embryo and fetus for a pregnant
woman to have a couple glasses of wine in the
evening.
 The same disease organism or chemical agent that
can do serious damage to a 6-week-old embryo may
have no effect on a 4-month-old fetus.
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Prenatal Development: Truth or Fiction?
 Babies can be born addicted to narcotics and other
drugs.
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
The Germinal Stage
Wanderings
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What Happens During the Germinal Stage?
• Period from conception to implantation (approximately 2 weeks)
• Zygote repeatedly divides but does not gain in mass
• Travels down Fallopian tube to uterus
• After 3 or 4 days, implants in uterine wall
– Takes form of blastocyst
• Trophoblast, outer membrane of blastocyst, differentiates into
membranes that will protect and nourish the embryo
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Figure 3.1 The Ovarian Cycle, Conception and the Early Days of the Germinal Stage
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
How Does the Dividing Mass of Cells Obtain
Nourishment During the Germinal Stage?
• Prior to implantation, the dividing cells are nourished by the yolk
of the original egg
• Once implanted, nourishment is obtained from the mother
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
The Embryonic Stage
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What Happens During the Embryonic Stage
of Prenatal Development?
• Begins with implantation (3rd week) through 8th week
• Major organs systems differentiate
• Developmental trends
– Cephalocaudal – head takes precedence over lower parts of the
body
– Proximodistal – central axis of body outward
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Figure 3.2 Human Embryos and Fetuses at Various Stages of Development
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What Happens During the Embryonic Stage
of Prenatal Development?
• Embryonic disk
– Ectoderm (outer layer) develops into nervous system, sensory
organs, nails, hair, teeth and skin
– Endoderm (inner layer) forms the digestive and respiratory systems,
liver, and pancreas
– Mesoderm (middle layer) develops into the excretory, reproductive
and circulatory system, muscles, skeleton and inner layer of skin
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
When Does the Heart Begin to Beat?
• Heart begins to beat (4th week)
• Arm buds and leg buds appear (4th week)
• Eyes, ears, nose and mouth begin to take shape
• Limbs are elongating, facial features become distinct (8th week)
• Teeth buds, working kidneys and liver (8th week)
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Sexual Differentiation
• Nondescript sex organs formed (5 to 6 weeks)
• Internal and external genitals at this stage resemble female
structures
• Sex organs begin to differentiate, based on genetic code (7th
week)
– Y chromosome causes testes to differentiate
– No Y chromosome causes ovaries to differentiate
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Figure 3.3 Development of the Internal Genital Organs from an Age of 5-6 Weeks
Following Conception
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Figure 3.4 Development of the External Genital Organs from an Undifferentiated Stage
at 5-6 Weeks Following Conception
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Sex Hormones and Sexual Differentiation
• Male hormonal influences
– Testes produce androgens
– Testosterone differentiates male duct system (Wolffian)
– DHT (dihydrotestosterone) triggers development of male external
genital organs
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Sex Hormones and Sexual Differentiation
• Female hormonal influences
– Small amounts of androgens are produced
• play a role in secondary sexual characteristics in adolescence
• important in sex drive of females
– Wolffian ducts degenerate and Mullerian ducts develop into
Fallopian tubes, uterus and inner part of the vagina
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
A Closer Look
Genetic Factors in Sexual
Differentiation
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
How Does the Embryo Get Nourishment
from the Mother?
• Amniotic Sac
– Protects the embryo/fetus within the uterus
– Sac is surrounded by amniotic fluid
• Placenta
– Mass of tissue exchanges nutrients and wastes between
embryo/fetus and mother
• Umbilical Cord
– Connects the fetus to the placenta
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Do Germs or Drugs in the Mother Pass Through
the Placenta and Affect the Baby?
• Placenta acts as a filter between the bloodstream of the mother
and the bloodstream of the embryo/fetus
• Oxygen and nutrients reach the embryo
• Carbon dioxide and waste pass to the mother
• Many germs and drugs may also reach the embryo
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
The Fetal Stage
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What Happens during the Fetal Stage
of Prenatal Development?
• Third month through birth
• End of first trimester
– Major organ systems formed
– Fingers and toes formed
– Eyes can be distinguished
– Sex of fetus can be determined visually
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What Happens during the Fetal Stage
of Prenatal Development?
• End of second trimester
– Opens and shuts eyes
– Sucks thumb
– Alternates between sleep and wakefulness
– Responds to light and sound
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What Happens during the Fetal Stage
of Prenatal Development?
• End of third trimester
– Heart and lungs increasingly able to sustain life
– Gains in weight and length
– During 7th month, fetus turns upside down in uterus
• Born at end of 7th month – 90% survival rate
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Fetal Perception
• Sound
– 13th week – fetus responds to sound waves
– During third trimester can discriminate pitch
• The Cat in the Hat study (DeCasper and Fifer, 1980)
– During final six weeks of pregnancy, Mothers read The Cat in the
Hat twice daily
– Using a special pacifier, newborns chose The Cat in the Hat read by
their mother
• Newborns prefer Mother’s voice
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
When Does the Mother Begin to Detect
Fetal Movements?
• Middle of 4th month – detect first fetal movements
• End of second trimester
– Fetus moves vigorously, turns somersaults
– Begins slow squirming movements
– Begins sharp jabbing and kicking movements
• As fetus grows, movements becomes restricted
• Prenatal activity predicts activity levels after birth
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Environmental Influences on
Prenatal Development
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
How Does the Nutrition of the Mother Affect
Prenatal Development?
• Malnutrition in mother (esp. during last trimester)
– Low birthweight, prematurity, stunted growth, retardation of brain
development, cognitive deficiencies, behavioral problems
• Overly slender mother
– Risk preterm deliveries and low birthweight
• Maternal obesity
– Linked to higher risk of stillbirth
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
How Does the Nutrition of the Mother Affect
Prenatal Development?
• Folic acid supplements
– Reduce risk of neural tube defects
• Obesity during pregnancy
– Increases risk of neural tube defects
• Mother can expect to gain 25 to 35 pounds during pregnancy
– Inadequate weight gain increase chance of premature or low-birthweight baby
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
How do Teratogens Affect Prenatal Development?
• Teratogen – environmental agents that can harm embryo or fetus
– Drug ingested by mother
– Substance produced by mother
– Heavy metals such as lead and mercury
– Excessive hormones
– Radiation
– Pathogens – bacteria and viruses
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Does it Matter When, during Pregnancy, a Women
is Exposed to a Teratogen?
• Critical periods of exposure to teratogens
– Based on development of organs
• Embryo is more vulnerable than fetus due to major organ
systems differentiating
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Figure 3.5 Critical Periods in Prenatal Development
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
A Closer Look
Spacing Children the Goldilocks
Way: What is “Just Right”?
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Maternal Health Problems?
• Sexually Transmitted Infections (STIs)
– Syphilis can cause miscarriage, stillbirth, or congenital syphilis
– About one-quarter babies born to HIV/AIDS infected mothers are
infected also
• Many are infected during childbirth
• HIV is also found in breast milk
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
A Closer Look
Preventing One’s Baby from
Being Infected with HIV
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Maternal Health Problems?
• Rubella (German measles)
– Viral infection may cause birth defects
• Toxemia
– Characterized by high blood pressure, may be linked to malnutrition
– May cause premature or undersized babies
– Cause of maternal death
• Rh Incompatibility
– Transfer of maternal antibodies that may cause brain damage or
death
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Drugs Taken by the Mother?
• Thalidomide
– missing or stunted limbs
• Antibiotics
– Tetracycline may lead to yellowed teeth and bone abnormalities
• Hormones
– Progestin can masculinize external sex organs of female embryo
– DES can cause cervical and testicular cancer
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Drugs Taken by the Mother?
• Vitamins
– High doses of vitamins A and D are associated with central nervous
system damage, small head size and heart defects
• Heroin and Methadone
– Maternal addiction linked to low birthweight, prematurity and
toxemia
– Baby may be born addicted
• Marijuana
– Risk of low birthweight, immature development of nervous system
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Drugs Taken by the Mother?
• Cocaine
– Maternal use of cocaine increases risk of stillbirth, low birthweight,
and birth defects
– In utero exposure results in problems throughout childhood
• Alcohol
– Alcohol passes through placenta and poses risks for death of fetus
and neonate, malformations, growth deficiencies
– Fetal Alcohol Syndrome (FAS)
• physical and psychological defects
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Drugs Taken by the Mother?
• Caffeine
– Connected with miscarriage and low-birthweight
• Cigarettes
– Nicotine and carbon monoxide pass through the placenta
• nicotine stimulates fetus
• carbon monoxide is toxic and decreases oxygen to fetus
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Environmental Hazards?
• Heavy metals (lead, zinc, mercury)
– Threatens cognitive development
• Prenatal exposure to PCBs
– Connected with smaller, less responsive babies
– More likely to develop cognitive deficits
• Fetal exposure to radiation
– Risks for neural and skeletal problems
• Fathers exposure to heavy metals and radiation may also cause
abnormalities in baby
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
What are the Effects of Maternal Stress?
• Maternal stress linked to secretion of hormones
– Adrenaline passes through placenta
• Connected to complications during pregnancy and labor
• Connected to low preterm, low-birthweight, and irritable babies
Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus
Chapter 3
Is the Parents’ Age Connected with the
Outcome of Pregnancy?
• Teenage mothers
– Higher incidence of infant mortality and low-birthweight children
• Women over age 30
– Increasing risk of chromosomal abnormalities, stillborn or preterm
babies