If you and your partner are newly pregnant, you may be amazed at
the number and variety of
prenatal tests
available to you. Blood tests, urine tests, monthly medical exams,
diet questionnaires, and family history tracking - each helps to
assess the health of you and your baby, and to predict any
potential health risks.
Unlike your parents, you may also have the option of
genetic testing
. These tests identify the likelihood of passing certain genetic
diseases or disorders (those caused by a defect in the genes - the
tiny, DNA-containing units of heredity that determine the
characteristics and functioning of the entire body) to your
children.
Some of the more familiar genetic disorders are:
If your history suggests that genetic testing would be helpful,
you may be referred to a genetic counselor. Or, you might decide to
seek out genetic counseling yourself.
But what do genetic counselors do, and how can they help your
family?
What Is Genetic Counseling?
Genetic counseling is the process of:
- evaluating family history and medical records
- ordering genetic tests
- evaluating the results of this investigation
- helping parents understand and reach decisions about what to
do next
Genetic tests are done by analyzing small samples of blood or
body tissues. They determine whether you, your partner, or your
baby carry genes for certain inherited disorders.
Genes
are made up of DNA molecules, which are the simplest building
blocks of heredity. They're grouped together in specific
patterns within a person's chromosomes, forming the unique
"blueprint" for every physical and biological
characteristic of that person.
Humans have 46 chromosomes, arranged in pairs in every living
cell of our bodies. When the egg and sperm join at conception, half
of each chromosomal pair is inherited from each parent. This newly
formed combination of chromosomes then copies itself again and
again during fetal growth and development, passing identical
genetic information to each new cell in the growing fetus.
Current science suggests that human chromosomes carry from
25,000 to 35,000 genes. An error in just one gene (and in some
instances, even the alteration of a single piece of DNA) can
sometimes be the cause for a serious medical condition.
Some diseases, such as Huntington's disease (a degenerative
nerve disease) and Marfan syndrome (a connective tissue disorder),
can be inherited from just one parent. Most disorders,
including cystic fibrosis, sickle cell anemia, and Tay-Sachs
disease, cannot occur unless both the mother and father pass along
the gene.
Other genetic conditions, such as Down syndrome, are usually not
inherited. In general, they result from an error (mutation) in the
cell division process during conception or fetal development. Still
others, such as achondroplasia (the most common form of dwarfism),
may either be inherited or the result of a genetic mutation.
Genetic tests don't yield easy-to-understand results. They
can reveal the presence, absence, or malformation of genes or
chromosomes. Deciphering what these complex tests mean is where a
genetic counselor comes in.
About Genetic Counselors
Genetic counselors are professionals who have completed a
master's program in medical genetics and counseling skills.
They then pass a certification exam administered by the American
Board of Genetic Counseling.
Genetic counselors can help identify and interpret the risks of
an inherited disorder, explain inheritance patterns, suggest
testing, and lay out possible scenarios. (They refer you to a
doctor or a laboratory for the actual tests.) They will explain the
meaning of the medical science involved, provide support, and
address any emotional issues raised by the results of the genetic
testing.
Who Should See One?
Most couples planning a pregnancy or who are expecting don't
need genetic counseling. About 3% of babies are born with birth
defects each year, according to the Centers for Disease Control and
Prevention (CDC) - and of the malformations that do occur, the
most common are also among the most treatable.
Cleft palate
and clubfoot, two of the more common birth defects, can be
surgically repaired, as can many heart malformations.
The best time to seek genetic counseling is before becoming
pregnant, when a counselor can help assess your risk factors. But
even after you become pregnant, a meeting with a genetic counselor
can still be helpful. For example, sometimes babies have been
diagnosed with spina bifida before birth. Recent research suggests
that delivering a baby with spina bifida via cesarean section
(avoiding the trauma of travel through the birth canal) can
minimize damage to the spine - and perhaps reduce the likelihood
that the child will need a wheelchair.
Experts recommend that all pregnant women, regardless of age or
circumstance, be offered genetic counseling and testing to screen
for Down syndrome.
It's especially important to consider genetic counseling if
any of the following risk factors apply to you:
- a standard prenatal screening test (such as the alpha
fetoprotein test) yields an abnormal result
- an amniocentesis yields an unexpected result (such as a
chromosomal defect in the unborn baby)
- either parent or a close relative has an inherited disease or
birth defect
- either parent already has children with birth defects or
genetic disorders
- the mother-to-be has had two or more miscarriages or babies
that died in infancy
- the mother-to-be will be 35 or older when the baby is born.
Chances of having a child with Down syndrome increase with the
mother's age: a woman has a 1 in 350 chance of conceiving a
child with Down syndrome at age 35, a 1 in 110 chance at age 40,
and a 1 in 30 chance at age 45.
- you are concerned about genetic defects that occur frequently
in certain ethnic or racial groups. For example, couples of
African descent are most at risk for having a child with sickle
cell anemia; couples of central or eastern European Jewish
(Ashekenazi), Cajun, or Irish descent may be carriers of
Tay-Sachs disease; and couples of Italian, Greek, or Middle
Eastern descent may carry the gene for thalassemia, a red blood
cell disorder.
Meeting With a Genetic Counselor
Before you meet with a genetic counselor in person, you'll
be asked to gather information about your family history. The
counselor will want to know of any relatives with genetic
disorders, multiple miscarriages, and early or unexplained deaths.
The counselor will also want to look over your medical records,
including any ultrasounds, prenatal test results, past pregnancies,
and medications you may have taken before or during pregnancy.
If more tests are necessary, the counselor will help you set up
those appointments and track the paperwork. When the results come
in, the counselor will call you with the news and often will
encourage you to come in for a discussion.
The counselor will study your records before meeting with you,
so you can make the best use of your time together. During the
session, you'll go over any gaps or potential problem areas in
your family or medical history. The counselor can help you
understand the inheritance patterns of any potential disorders and
help assess your chances of having a child with those
disorders.
The counselor will distinguish between risks that every
pregnancy faces and risks that you personally face. Even if you
discover you have a particular problem gene, science can't
always predict the severity of the related disease. For instance, a
child with cystic fibrosis can have debilitating lung problems or,
less commonly, milder respiratory symptoms.
After Counseling
Genetic counselors can help you understand your options and
adjust to any uncertainties you face, but you and your family will
have to decide what to do next.
If you've learned prior to conception that you and/or your
partner are at high risk for having a child with a severe or fatal
defect, your options might include:
- pre-implantation diagnosis - when eggs that have been
fertilized in vitro (in a laboratory, outside of the womb) are
tested for defects at the 8-cell (blastocyst) stage, and only
nonaffected blastocysts are implanted in the uterus to establish
a pregnancy
- using donor sperm or donor eggs
-
adoption
If you've received a diagnosis of a severe or fatal defect
after conception, your options might include:
- preparing yourself for the challenges you'll face when
you have your baby
- fetal surgery to repair the defect before birth (surgery can
only be used to treat some defects, such as spina bifida or
congenital diaphragmatic hernia, a hole in the diaphragm that can
cause severely underdeveloped lungs. Most defects cannot be
surgically repaired.)
- ending the pregnancy
For some families, knowing that they'll have an infant with
a severe or fatal genetic condition seems too much to bear. Other
families are able to adapt to the news - and to the birth -
remarkably well.
Genetic counselors can share the experiences they've had
with other families in your situation. But they will not suggest a
particular course of action. A good genetic counselor understands
that what is right for one family may not be right for another.
Genetic counselors can, however, refer you to specialists for
further help. For instance, many babies with Down syndrome are born
with heart defects. Your counselor might encourage you to meet with
a cardiologist to discuss heart surgery, and a neonatologist to
discuss the care of a post-operative newborn. Genetic counselors
can also refer you to social workers, support groups, or mental
health professionals to help you adjust to and prepare for your
complex new reality.
Finding a Genetic Counselor
Working with a genetic counselor can be reassuring and
informative, especially if you or your partner have known risk
factors. Talk to your doctor if you feel you would benefit from
genetic counseling. Many doctors have a list of local genetic
counselors with whom they work. You can also contact the National
Society of Genetic Counselors for more information.
Reviewed by:
Linda Nicholson, MS, MC
Date reviewed: April 2007
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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