Chapter 4: Prenatal Development
4.1 The Developing Baby
4.2 Problems in Prenatal Development
4.3 Avoiding Dangers to the Baby
Chapter 4 Objectives
•List the methods of family planning
•Outline what occurs during each of the three stages of prenatal
development
•Contrast miscarriage and stillbirth
•Identify how ten major birth defects can be diagnosed
•Summarize the hazards that alcohol and other drugs pose to prenatal
development
•Assess why environmental hazards must be avoided during
pregnancy
•Describe how a fetus can be affected by certain illnesses the mother
The Developing Baby
Chapter 4 Section 1
Family Planning
Many families carefully consider whether to have children
and when to have them. However, anytime a couple has
sexual intercourse, a pregnancy can occur. The only sure
way to prevent pregnancy is abstinence, or avoiding
sexual activity.
Do you think this statement is true or false?
Conception
About every 28 days, an ovum (egg) is released by one of a
woman’s two ovaries.
This is called ovulation; at the same time certain hormones are
released
During ovulation, the inner lining of the uterus grows and
thickens.
If the ovum is not fertilized, the lining breaks down and passes
out of the body
The menstrual period
When an ovum is released it travels through the fallopian
tube (connects the ovary to the uterus)
This journey takes about 2-3 days
Conception
When the ovum reaches the uterus unfertilized, it typically
breaks up
When a sperm, the male cell, reaches the fallopian tube
it may penetrate and fertilize the ovum
The process when the sperm fertilizes the egg is called
conception
Ovum's usually live 12-24 hours while sperm are capable
of fertilizing an ovum for about 48 to 72 hours
During a woman’s cycle, there are only about 3-4 days in
which conception can occur
Conception
The Role of Genetics
People inherit many physical traits from their parents
Skin color
Hair color and texture
Eye color
Size and shape of ears
Much more…
Some children are more likely to have talents like musical
talents or athletic ability
The Role of Genetics
At the moment of conception, every human baby receives
46 chromosomes
A chromosome is a tiny threadlike structure in the nucleus of
every cell
Chromosomes come in 23 pairs
The fathers sperm and mothers ovum contribute 1 to
each pair
Has hundreds to thousands of gene
A gene is a unit that determines a human’s inherited
characteristics
The complete blueprint for the creation of a person is called
a genome
The complex molecules that make up genes are called DNA
Dominant and Recessive Genes
Dominant
Recessive
A dominant gene is a
stronger gene
A recessive gene is a
weaker one and will not be
expressed
•The terms dominant and recessive only refer to the relationship of
genes to each other
•What factor determines the characteristic that a person will express is
the dominant gene
•EX: Red hair genes often skip a generation because the gene is
recessive
•Most traits are influenced by multiple genes
•Height, weight, personality, and intelligence
Let’s Practice
Making a Unique Person
Heredity explains why people in some families look so
much alike and why some do not
EX: one child with brown hair and another with bright blond
hair
The gender of the child is
determined at conception
Sex chromosomes come in
two types X and Y
Woman carries the X, and the
man carries the X or Y
1st Month
At 2 weeks: size of a pin
head
Egg attaches to the lining
of the uterus
Critical stage for brain and
spinal cord development
Internal organs and
circulatory system begin to
form
The heart begins to beat
2nd Month
Size about ¼” long at the
beginning of the month
Face, eyes, ears, and limbs
take shapes
Bones begin to form
3rd Month
Size about 1” as the month
begins
Nostrils, mouth, lips, and
eyelids form
Buds for all 20 baby teeth
appear
Fingers and toes almost
complete
All organs present but still
immature
4th Month
About 3” long; weighs 1
ounce as the month
begins
Can suck its thumb,
swallow, hiccup, and
move around
Facial features become
clearer
5th Month
About 6 ½’-7” long and
weighs 4-5 oz as month
begins
Hair, eyelashes, and
eyebrows appear
Teeth continue to develop
Organs are maturing
Becomes more active
6th Month
Size about 8-10” long and
weighs 8-12 oz. as the
month begins
Fat deposits under skin, but
fetus appears wrinkled
Breathing movements
begin
7th Month
Size about 10-12” long and
weighs 1 ½-2 lbs as month
begins
Has periods of activity
followed by periods of rest
and quiet
8th Month
Size about 14-16” long, 2
½-3 lbs as the month
begins
May react to loud noises
with a reflex jerking action
Moves into a head-down
position
9th Month
Size about 17-18” long and weighs
about 5-6 lbs as month begins
Weight gain continues
Skin becomes smooth as fat
deposits continue to form
Movements decrease as the fetus
has less room to move around
Acquires disease-fighting
antibodies from the mother’s blood
Descends into pelvis, ready for
birth
Chapter 4 Section 2
Problems in Prenatal Development
Losing a Baby
Sometimes a baby does not develop normally
Sometimes the developing baby dies
Miscarriage is when a baby dies prior to the 20th week of
pregnancy
Still birth is when a baby dies after the 20th week of pregnancy
About 15% of recognized pregnancies end in miscarriage
Causes are still not medically known
Still birth occurs in about 2% of pregnancies
Most common causes are problems with the placenta, abnormal
chromosomes, poor growth, and infections
Dealing with Grief
Most couples feel a long sense of attachment prior to a
baby’s birth
May go through similar stages of grief that a parent would to
a child that was already born
Parents may blame themselves and feel alone
Couples may need support to deal with grief
Most couples that experience a miscarriage or stillbirth
still have healthy children later
Birth Defects
A serious problem that threatens a baby’s health, and is
present at birth, is called a birth defect
Some are mild that no one would ever know the child
has a birth defect
Others can result in disabilities or even death
Approximately 120,000 babies are born each year in the
US with a birth defect
Scientists are still trying to identify some causes
If found, could possibly decrease the occurrence of birth
defects
Types and Causes of Birth
Defects
Some defects cause an
abnormality in the structure
of the body
EX: extra or missing
fingers/toes
Some defects cause one
or more systems in the
body to not function
properly
EX: blindness, deafness,
and mental retardation
Some abnormalities are
not discovered until
months or years after birth
4 main causes of birth
defects currently:
Environment
Hereditary
Errors in chromosomes
Combination of
environment and
hereditary factors
Types and Causes of Birth
Defects
Environmental
Hereditary
Nutritional balance of the
mothers diet
Parents can pass off faulty
recessive genes
Any diseases or infection the
mother has
Harmful substances; alcohol,
over-the-counter medication,
illegal drugs, etc.
Some medicines help the
mother but hurt the baby
Air pollution
Exposure to X-Rays and high
levels of radiation
This is called recessive
inheritance
Tay-Sachs disease
Cystic Fibrosis
Types and Causes of Birth
Defects
Errors in Chromosomes
When a baby has too many or too
few chromosomes
Most common birth defect is Down
syndrome
1 in 800 children are born with
a form of Down syndrome
When you have too many or too
few it can affect the body’s
systems
Heart defects
Leukemia
Poor muscle tone
Physical growth or motor
development
Interactions of Heredity
and Environment
When an environmental and
hereditary factors are
present
Examples
Cleft lip
Cleft palate
Heredity and
medications
Spina bifida
A predisposition,
tendency, are
combined
medications
during pregnancy
Prevention and Diagnosis
Changing of your lifestyle
Frequent doctors visits for prenatal check-ups
Genetic counseling
Assesses their risk of having a child with a birth defect that is
caused by a defect in genes
Compiling a family history
Prenatal Tests
More than 100 kinds of birth defects can be detected
before birth
Prenatal Tests
Alpha-fetoprotein
(AFP)
Blood test between 15 and
20 weeks
AFP is produced in the liver
of the fetus and shows up
in the mothers blood
Abnormal levels can
indicate a possible birth
defect
Ultrasound
Is a test that uses sound
waves to make a video
image of an unborn baby
Can monitor problems with
a baby’s skeletal,
circulatory, or nervous
system
Usually during their 20th week
Many doctors now do 3D
ultrasounds
Prenatal Tests
Amniocentesis
The process of withdrawing a
sample of the amniotic fluid
surrounding the unborn baby
Often used as a test for Down
syndrome with the mother is
older than 35 years or older
Also may be completed if
uncertain results are obtained
from the AFP
Done between the 15th and 20th
week
Chorionic Villi
Sampling
Uses a sample of tissue
from the membrane that
encases the fetus to check
for birth defects
Tissue is cut off and
analyzed
Chapter 4 Section 3
Avoiding Dangers to the Baby
Effects of Alcohol and Other Drugs on
Pregnancy
Essential parts of good prenatal care is avoiding hazards
such as
Alcohol
Drugs
Smoking
X-Rays
Hazardous chemicals
Other harmful substances
Infections
Environmental Factors
Alcohol
Fetal Alcohol Syndrome
Even small amounts can harm
the baby
Doctors do not know the exact
amount that can harm a baby
Avoid any amounts when
trying to become pregnant
Incurable condition found in
some children of mothers that
consumed alcohol during
pregnancy
1 in 5 babies born with FAS do
not live to 1 year old
Those that survive can have
problems
Delayed physical growth
Heart, liver, kidney defects
Hyperactivity
Facial deformity
Mental retardation
Learning Disabilities
Alcohol
Fetal Alcohol Effects
Abnormalities caused by
the mother consuming
alcohol during pregnancy
Suffer less than children
with FAS
Extent of damage is
directly related to the
amount the mother drinks
Binge drinking increases
your risk of having a
child with FAS
Prescription Drugs and Over-TheCounter Drugs
Extreme example of unsafe mediation is thalidomide
1950s- to relieve morning sickness
After proved harmful, 5,000 babies were born with birth defects
Missing or deformed arms, legs
Some acne medicine has been proven to cause problems
Chemicals found in some medications can cause mental
retardation in the first 3 months
4-9 months, OTC drugs can cause slow growth, infections, and
bleeding at birth
Caffeine
Passes easily through the
placenta
Cause high blood levels
of caffeine for fetus
Increases fetal heart rate
and movement
Consumed in large amounts:
Miscarriage
Premature birth
Low birth weight
Can draw fluid and calcium
out of the body
Small amounts (2 cups of
coffee or soft drinks per day)
not a huge risk
Tobacco
Cause:
Low birth weight
Premature birth
Linked to:
Respiratory infections
Allergies
Illegal Drugs
Mothers pass their addiction to
their baby
After birth, babies must go
through a painful period of
withdrawal
Long-term effects can be
learning and behavioral
disabilities
Cocaine causes miscarriage, still
birth, and premature births
Causes unborn child to have
strokes resulting in brain and
heart damage or even
death
Low birth weight
Smaller heads
Risk of seizures
Risk of SIDS (sudden infant
death syndrome)
Tremors
Exaggerated startle response
Irritability and
developmental delays
Feeding and sleeping
problems
Illegal Drugs
Marijuana and
methamphetamine use is
liked to low birth weight
and premature delivery
Breathing problems
Poor attention span
Drowsiness
Heart defects
Environmental Hazards
Two possible hazards to unborn babies include X-rays
and hazardous chemicals.
Radiation from X-rays, or from other sources, can cause
birth defects
If an X-ray is necessary during pregnancy, inform your
medical staff because precautions can be taken
Dental X-rays are generally considered safe
Environmental Hazards
Hazardous Substances and Chemicals
Paint
Pesticides
Lead in water or paint
Carbon monoxide
Mercury found in some fish
Solvents, paint thinners, and formaldehyde
Diseases and Infections
Rubella
Toxoplasmosis
Rubella is also called the
German measles
Caused by a parasite
Most people have immune systems to
fight it off
Developing babies cannot
Causes:
Blindness
Hearing loss
Learning disabilities
Severe cases
Death
Long-term learning
disabilities
Precautions:
Never clean a cats litter box
Mother contracts it
Birth defects can happen
within 1st three months
Blindness
Deafness
Heart disease
Mental retardation
Diseases and Infections
Chicken Pox
Sexually Transmitted
Infections
Viral infection
Passed from mother to baby
Depending when infection
occurs during pregnancy will
affect the outcome to the baby
For Example:
1st half of pregnancy
Congenital Varicella
Syndrome
Causes scarring of the
skin, limb defects, eye
problems
Some cases miscarriage
Syphilis can be treated if
caught early to the
unborn baby
Can cause skin rash or
lesions, bone/facial
deformities, deafness,
brain damage
2% end in miscarriage,
stillbirth, or death
