CHAPTER 4
PRENATAL DEVELOPMENT
Section 3- Problems in
Prenatal Development
LOSING A BABY
• Sometimes a pregnancy begins, but the baby doesn’t
develop normally. In some of those cases, the baby dies. If this
happened prior to the 20th week of pregnancy, the event is
called a miscarriage. If they baby dies after that time, it is
called a stillbirth.
• Unfortunately, miscarriages are not all that uncommon.
Approximately 15 to 20 percent of all recognized pregnancies
end in miscarriage. Medical professionals don’t completely
understand that causes.
• Stillbirth occurs in about 2 percent of pregnancies. The most
common causes are problems with the placenta, abnormal
chromosomes, poor growth, and infections.
DEALING WITH GRIEF
• The loss of a child by miscarriage or stillbirth can be very
unexpected or painful for parents. Most couples look
forward to a baby’s birth and feel a great sense of
attachment long before the birth. When they lose their
baby, they may go through stages of grief similar to those
experienced by the loss of a child that was already born.
Sometimes, these parents feel terribly alone and may
blame themselves for the death. In most cases, however,
these tragedies are completely beyond the parents’
control. Couples may need support to work through their
grief. Most couples who suffer a miscarriage or stillbirth are
later able to have healthy children.
TYPES OF BIRTH DEFECTS
Birth Defect
Description
Causes
Detection
Treatment
Cerebral Palsy
Cerebral palsy is a
general term for a
variety of problems of
the motor system. The
symptoms can include
lack of coordination,
stiffness, jerkiness,
difficulty with speech,
and paralysis.
Results from
damage to
the brain
before,
during, or
shortly after
birth. The
causes vary.
The symptoms
usually appear
during the first
year of life. The
child usually
does not
develop motor
skills as quickly
as other babies.
The damage
caused to the
brain is
irreversible.
However,
physical
therapy, speech
therapy, surgery,
and medication
can often lessen
the effects of
the damage.
Cleft Lip and/or Cleft
Palate
A gap in the upper lip
or palate (roof of the
mouth) causes
problems with eating,
swallowing, speech,
and appearance.
Condition
may be
caused by
hereditary or
environment
al factors or
both.
Both cleft lip
and cleft palate
are apparent at
birth. They can
often be
detected by
ultrasound
before birth.
Surgery corrects
the gap and
helps eliminate
problems
associated with
it.
TYPES OF BIRTH DEFECTS
Birth Defect
Description
Causes
Detection
Treatment
Cystic Fibrosis
Cystic Fibrosis (CF)
affects the respiratory
and digestive systems.
Many with CF die
before reaching
adulthood, although
treatment now allows
sufferers with the
condition to live longer
than in the past.
It is far more
likely to affect
Caucasians
than African or
Asian
Americans. CF
is caused by
inheriting
defective
recessive genes
from both
parents.
Symptoms
include very
salty sweat and
a cough that
doesn’t go
away. Blood
tests can
identify carriers
of the gene
and sweat tests
can diagnose
an affected
child.
There is no known
cure. Those with CF
can be helped
through special diets,
lung exercises, and
therapies and
medication to help
treat symptoms.
Down Syndrome
A group of problems
that may include,
among other
conditions, mental
retardation; problems
of the heart, blood,
and digestive system;
and poor muscle tone.
Down
syndrome is
caused by the
presence of an
extra
chromosome
21.
It can be
detected in a
fetus by
amniocentesis
or chorionic villi
sampling, or
after birth by a
blood test.
Treatment includes
therapy, special
educational
assistance, and in
some cases corrective
surgery. The earlier
treatment begins, the
better for the child.
TYPES OF BIRTH DEFECTS
Birth Defect
Description
Causes
Detection
Treatment
Muscular Dystrophy
There are many
different types of
muscular dystrophy; all
involve a progressive
weakness and
shrinking of the
muscles. The most
common form begins
between the ages of
two and six.
Most types of
muscular
dystrophy are
hereditary. The
most common
form is
transmitted by
female carriers
of the gene
but affects
only males.
The disease is
recognized
once
symptoms
appear.
Genetic
counseling
can identify
carriers.
There is no
known cure.
Physical therapy
can minimize the
disabilities.
PKU
PKU (phenylketonuria)
is a condition in which
the body is unable to
process and use a
specific protein that is
present in nearly all
foods. Brain damage
and mental
retardation can result.
A child with
PKU inherits
defective
recessive
genes from
both parents.
Newborns
are tested for
PKU, as
required by
law in all
states.
There is no
known cure for
PKU. If it is
diagnosed early,
a special diet
can reduce or
prevent brain
damage.
TYPES OF BIRTH DEFECTS
Birth Defect
Description
Causes
Detection
Treatment
Sickle Cell Anemia
Malformed
red blood cells
interfere with
the supply of
oxygen to all
parts of the
body. The
symptoms
include
tiredness, lack
of appetite,
and pain.
Sickle cell
anemia can
lead to early
death.
Sickle cell
anemia is
caused by
inheriting
defective
recessive genes
from both
parents. African
Americans are
more likely to
have this
condition than
any other group.
Amniocentesis
or chorionic villi
sampling can
identify sickle
cell anemia in a
fetus. Genetic
counseling can
identify parents
who carry the
gene. Blood
tests can show
the presence of
the condition
after birth.
There is no
known
cure for
sickle cell
anemia.
Medication
can treat
the
symptoms.
TYPES OF BIRTH DEFECTS
Birth Defect
Description
Causes
Detection
Treatment
Spina Bifida and
Hydrocephalus
In spina bifida, an
incompletely
formed spinal cord
may lead to stiff
joints, difficulty
moving the legs,
partial paralysis,
and problems with
the kidneys and
urinary tract.
Seventy out of
every 100 children
with spina bifida
also have
hydrocephalus, in
which an excess
of fluid surrounds
the brain.
The problem
seems to be
caused by a
combination
of hereditary
and
environmental
factors. Taking
a folic acid
supplement
during
pregnancy
may help
reduce
incidence.
Spina bifida is
apparent at
birth.
Hydrocephalus
is indicated by
overly rapid
growth of the
head. Tests of
the mother’s
blood,
amniocentesis,
and ultrasound
can reveal
suspected
cases in a
fetus.
Corrective
surgery,
physical
therapy, and
special
schooling can
minimize
disabilities
cause by spina
bifida.
Hydrocephalus
can be helped
by surgically
implanting a
shunt that
relieves the
fluid that has
built up.
TYPES OF BIRTH DEFECTS
Birth Defect
Description
Causes
Detection
Treatment
Tay-Sachs Disease
Babies born with
Tay-Sachs
disease lack a
certain
chemical in their
blood that
makes their
bodies unable to
process and use
certain fats in
the brain and
nerve cells. The
condition leads
to severe brain
damage and to
death, usually by
the age of four.
Tay-Sachs
disease is
caused by
inheriting
defective
recessive
genes from
both
parents. It is
most
common in
families of
eastern
European
Jewish
descent.
Amniocentesis
or chorionic villi
sampling can
identify TaySachs disease in
a fetus. Blood
tests can
identify those
who carry the
defective gene
and can test for
the condition
after birth.
There is no
known cure
for this
disease.
Treatment
consists of
doing
everything
possible to
make the
child
comfortable.
WHAT CAN A CONCERNED COUPLE
DO ABOUT GENETIC BIRTH DEFECTS?
• For some couples, considering having a baby brings up concerns
about genetic birth defects. This typically happens if the inherited
diseases seem to occur in the family of one or both of the couple.
The first step would be for the couple to share their concerns with
their family doctor or obstetrician. If there is a family history of one
specific disease or symptoms of a genetic disorder, individuals
may wish to be tested. There are a few different types of genetic
testing Prior to pregnancy, testing can show whether a person
carries the traits for cystic fibrosis, Tay-Sachs disease, or sickle cell. If
necessary, the doctor can refer the couple to a genetic counselor.
• THINKING IT THROUGH- Discuss possible ethical, legal, and social
issues regarding genetic testing. How do you feel about these
issues?
CAUSES OF BIRTH DEFECTS
• At this time, scientists don’t fully understand the exact
causes of most birth defects. However, they are
constantly working to understand why they occur; which
they hope will lead to two wars for these condition. So
far, they have determined that there are four main
causes for birth defects, and research is continuing in
each area. Factors in the environment of the developing
baby cause some birth defects. Hereditary factors cause
others. Abnormal genes or chromosomal errors can also
cause birth defects, and some are caused by a
combination of environmental and hereditary factors.
ENVIRONMENTAL CAUSES
• During the first few weeks after conception, a baby
develops all the bodily systems needed for survival and a
healthy, normal life. During this time, the developing
baby depends completely on the mother’s body for
nourishment and oxygen.
• This early development is critical and many choices the
mother makes, possibly even before she knows she is
pregnant, can affect the lifelong health of her baby.
There may also be environmental factors that the mother
is unaware of that can affect the development of the
baby.
ENVIRONMENTAL CAUSES
(CONTINUED)
• Some environmental causes of birth defects include the
following:
• The nutritional balance of the mothers diet.
• Any diseases or infections a mother has during pregnancy.
• Harmful substances the mother consumes, including
alcohol, over-the-counter medications, and illegal drugs.
• Some medicines that benefit the mother, but hurt the
baby.
• Exposure to hazards, such as certain chemicals, high levels
of radiation, and X rays, especially early in pregnancy.
HEREDITARY FACTORS
• Every person has approximately 20,000 to 25,000 genes that
not only determine traits such as eye color and height, but
also directed the growth and development of every system in
the body. Half of each child’s genes come from the mother
and half from the father. Children typically get five or six
imperfect recessive and genes passed on to them. In the
majority of cases, though, a single copy of an imperfect
recess if the gene will have no affect on the development of
the baby. However, sometimes both parents will pass on the
same imperfect recessive gene, causing the baby to have a
birth defect. This is called recessive inheritance. Two
examples of conditions caused by recessive inheritance are
Tay-Sachs disease and cystic fibrosis.
HEREDITARY FACTORS (CONTINUED)
• Sometimes a child inherits a defective gene that is dominant.
It is only necessary for this gene to be passed on by one
parent for the child to have the birth defect. This is called
dominant inheritance. Huntington’s disease is a condition
caused by dominant inheritance. Some inherited conditions
only affect one sex. Hemophilia, a condition that prevents the
blood from clotting, is passed on from the mother only to her
sons. Like color blindness and Duchenne muscular dystrophy,
hemophilia usually only affects males.
ERRORS IN CHROMOSOMES
• Several types of birth defects
are caused by problems in the
number or structure of
chromosomes. An error may
occur when an egg or sperm
cell is developing, causing a
baby to have too many or too
few chromosomes or to have
broken or rearrange the
chromosomes. These are not
hereditary defects because
neither parent has the
abnormal chromosome.
ERRORS IN CHROMOSOMES
(CONTINUED)
• The most common birth defect of this type is Down syndrome.
A child with Down syndrome may have some degree of mental
retardation, plus physical problems. One in 800 to 1,000 babies
has this condition. Under normal conditions, each sperm and
egg cell carries 23 chromosomes. Sometimes an error occurs
when an egg or sperm cell is forming, causing there to be an
extra copy of chromosome 21. Instead of having two copies of
chromosome 21, a child has three because each chromosome
Carries hundreds of gene, the defect and interfere with element
in many ways including an increased risk of heart defects and
leukemia, poor muscle tone, problems with vision and hearing,
delayed physical growth and motor development, and
distinctive physical characteristics. Their risk for having a child
with Down syndrome is higher for older mothers.
INTERACTION OF HEREDITY
AND ENVIRONMENT
• Some birth defects are caused by a combination of heredity and the
environment. For example, a child may inherit the tendency that may
later lead to a heart defect. If a factor such as a drug or virus affects the
baby during pregnancy, the baby will have the heart defect. If the baby
did not inherit the gene for the heart defect, or did not get exposed to the
drug or virus, the heart would be normal. Because both the inherited
factor and the environmental factor were present, the baby’s heart had a
defect.
• Birth defects such as cleft lip, cleft palate, and spinal bifida may be
caused by a combination of hereditary and environmental factors. Both
cleft lip and cleft palates may be caused by a number of inherited genes
in combination with exposure during pregnancy to certain medications,
infections, illnesses, and tobacco or alcohol. The genetic predisposition for
spinal bifida, combined with the use of medications for the treatment of
diabetes and a seizure disorder during pregnancy, increase the likelihood
of a child having the defect.
PREVENTION AND DIAGNOSIS
OF BIRTH DEFECTS
• It can be challenging for a child born with a serious birth defect to
lead a normal, productive life. Other family members are
affected by the emotional and financial strain the defect causes.
However, advances in treatment and support groups are helping
children and their families cope. While not all causes of birth
defects can be anticipated or controlled, there are several things
that couples can do to minimize the chances of having a child
with birth defects.
• Before it even trying to conceive, perspective parents can
schedule the checkup to evaluate their overall health. They can
discuss lifestyle changes that may improve their chances for a
successful pregnancy and healthy baby. For example, women
should stop using tobacco and alcohol prior to pregnancy, as
these substances can lead to health problems and birth defects.
PREVENTION AND DIAGNOSIS
OF BIRTH DEFECTS (CONTINUED)
• Because many women do not know they are pregnant in the
early weeks, it is safer to quit smoking and drinking before there is
even the possibility of pregnancy. Men, too, are advised to either
cut back on or avoid alcohol, as it has been linked to low sperm
count.
• One said she is pregnant, the expectant mother can visit her
doctor for prenatal care. Such care goes a long way toward a
successful pregnancy, as her doctor can monitor her health and
the baby’s growth and development. The mother can also
continue to abstain from alcohol, illegal drugs, and tobacco. She
can talk to her doctor about the effects of any over-the-counter
and prescription medications on her baby. She should not take
any medication that is not approved by her doctor.
GENETIC COUNSELING
• Some people seek genetic counseling to assess their risk of having a
child with a birth defect that is caused by a defect in the genes. The
patients might be a couple who wish to have a child but are
concerned about having a child has a serious birth defects. There
may be a history of birth defects in the family. Some couples may
already have a child with a birth defect and want to learn more
about the risks for subsequent children. Genetic counselors don’t tell
people what to do about the information they receive; they only
explaining the options and risks.
• Family doctors can perform genetic counseling, but most patients
are referred to a genetic counselor. This specialist usually begins
working with a couple by evaluating the family history of both the
mother and the father. This includes information relating to the
medical histories, diseases, and causes of death of all known family
members.
GENETIC COUNSELING (CONTINUED)
• Along with their family history, a genetic counselor will usually request
a complete physical examination for both parents. If specific birth
defects are of concern, some other members of the family may
receive physical examinations as well. Special laboratory tests may
also be performed. Small samples of blood and body tissue may be
analyzed. For example, a blood sample can be tested to determine
whether the parents are carriers for the gene that causes cystic
fibrosis.
• Once all of the testing is complete, the genetic counselor can
usually tell the couple what their risks are for having a child with
certain genetic birth defects. It is the couple’s decision whether or
not to have children. If they do, they will be aware of extra testing
that may be needed during pregnancy to closely monitor the
development of the baby.
PRENATAL TESTS
• More than 100 kinds of birth defects can now be detected
before a baby is born there are many tests that are standard for
prenatal care in this country that help a doctor decide whether
or not a baby might have a birth defect. These tests can help
determine what treatments, if any, are necessary for the child
before or after birth.
• Sometimes prenatal tests are simple blood test. Other tests
involve procedures that carry more risks. The couple must
weigh the potential value of the information to be gained
against possible risks for the developing baby or the mother.
• Prenatal tests include: alpha-fetoprotein (AFP), ultrasound,
amniocentesis, and chorionic villi sampling.
ALPHA-FETOPROTEIN (AFP)
• This blood test is performed
on the expectant mother
between weeks 15 and 20
of a pregnancy. AFP is a
protein produced in the
liver of the fetus that is
detectable in the mother’s
blood. Abnormal AFP
levels can indicate a
possible birth defect.
Further testing can be
done to determine if a
birth defect does exist and
what it might be.
ULTRASOUND
• Ultrasound uses sound waves to make a video image,
called a sonogram, of an unborn baby. It can help the
doctor monitor the development of the baby, pinpoint
the baby’s age, and detect certain birth defects.
Problems with the baby’s skeletal, circulatory, or nervous
system may be detected during an ultrasound. The
sonogram also helps confirm the due date and the
presence of more than one fetus.
• Many women have an ultrasound during their pregnancy,
usually near the 20th week. Many doctors now perform 3D
ultrasounds, which provide more detailed images and
information about the baby’s development. While
research has shown that an ultrasound poses no threat to
the unborn child or the mother, it should be performed
only when there is a real medical reason for doing so.
AMNIOCENTESIS
• The process of withdrawing a sample of the amniotic fluid
surrounding the unborn baby is called amniocentesis. The
doctor uses the view from an ultrasound to guide a
needle through the mother’s abdomen into the amniotic
sac. Some cells from the fetus are in the amniotic fluid.
The sample is taken to a lab and tested for evidence of
birth defects and other health problems.
• Amniocentesis is most often used as a test for Down
syndrome when the expectant mother is over age 35.
The test may also be performed after questionable results
have been obtained through an ultrasound or the AFP
blood test. Amniocentesis involves some risk to the fetus
and is performed only when there is a strong medical
reason to do so.
CHORIONIC VILLI SAMPLING
• Chorionic villi sampling uses a
sample of the tissue from the
membrane that encases the fetus
to check for specific birth defects.
Samples of that as you are
snipped or suctioned off and
analyzed.
• Chorionic villi sampling tests for the
same disorders as amniocentesis,
but it is used less often because its
risks are much greater. One
advantage is that it can be
performed much earlier in the
pregnancy than amniocentesis.
PRENATAL TESTS (CONTINUED)
• Several other methods of prenatal diagnosis are now in
the experimental stages. These may someday provide
more accurate information at earlier stages of
development. For example, it is possible to view the
fetus directly through a special instrument called a
laparoscope. Doctors can also obtain samples of fetal
blood and tissue and even perform surgery on an
unborn child. Currently, these procedures carry a risk.
Further advances in medical research and technology
may make these procedures and safe enough for
widespread use.
SECTION 4-3 REVIEW QUESTIONS
1) How are a miscarriage and a stillbirth similar? How are they
different?
2) What is the cause of Down syndrome? What is one factor
that increases the risk of Down syndrome?
3) What group is most likely to have sickle cell anemia?
4) What are the four categories of birth defects?
5) Why might a person who has a parent with a genetic birth
defect want to consult with a genetic counselor?
6) What steps are involved in the genetic counseling process?
7) What are the two most common tests that check for
possible birth defects during pregnancy?