What is genetic screening?
If you are planning to have a baby, you may be concerned
about illnesses in one or both sides of your family that a
child might inherit. You can ask your health care provider
for genetic counseling or screening. Genetic screening is
a way to learn more about inherited diseases.
It is best to have genetic screening before you are
pregnant. It may also be done at your first prenatal visit
and later in your pregnancy.
When is it used?
Some of the reasons for a couple to have genetic screening
are:
- The mother will be 35 years old or older at the time of
delivery.
- You have had a child with an inherited disease or birth
defect.
- Someone in the family has had mental retardation or
other chromosome problems.
- You have had stillbirths or several miscarriages.
Stillbirths are babies born dead after 28 weeks of
pregnancy.
- Something about the pregnancy is not normal. For
example, blood test results have been abnormal. Or
there is too much or not enough amniotic fluid around
the baby.
- Someone in your family has had thalassemia. This is a
disorder that causes abnormal red blood cells. It is
most common in people from Asia and Mediterranean
countries (for example, Italians and Greeks).
- Someone in your family has had Tay-Sachs disease. This
is a brain problem that can cause early death. It is
most common in Jews who have an Eastern European
Ashkenazic ancestry.
- Members of your family have had other inherited
problems, such as hemophilia, cystic fibrosis, or
fragile X syndrome.
- Someone in your family has had sickle cell anemia. This
problem causes abnormal red blood cells. It is most
common in North American blacks.
- The mother had diabetes before she became pregnant.
How do I prepare for genetic screening?
Learn the medical history of members of your family. Try to
get details of any inherited diseases in your family. Ask
your parents if there have been any children in their
families who have been retarded or disabled, or who had
other birth defects.
Be ready to give the following information about yourself:
- past miscarriages
- exposure to chemicals, radiation (including x-rays), or
other environmental hazards before or during pregnancy
(for example, at work or from hobbies)
- any history of drug or alcohol abuse
- prescription, nonprescription, and herbal medicines taken
during pregnancy, including before you knew you were
pregnant.
Thinking carefully about your beliefs and goals will help
prepare you to make choices that are best for you and your
family. It's very important to discuss your choices and
options before you find out any test results.
How is genetic screening done?
Your health care provider or genetic counselor will review
your family and personal medical histories. You will be
asked about diseases, disorders, and birth defects in your
families. Both parents may have blood tests. If you are
pregnant, tests of the baby may also be done.
The following tests may be used to look for birth defects
and inherited diseases when you are pregnant:
- Tests of the mother's blood, including a check of the
level of alpha fetoprotein (AFP). AFP is a protein made
by the baby. The AFP test is done between the 15th and
18th weeks of pregnancy. If the amount of AFP is high or
low, your health care provider may do other tests. The
tests look for defects in the nervous system called
neural tube defects, such as spina bifida. They also
look for chromosome defects, such as Down syndrome.
- Ultrasound scans to check the baby for birth defects of
the brain, heart, spine, legs, arms, or other organs.
- Chorionic villus sampling to test a sample of tissue from
the placenta for chromosomal problems. This test is done
between the 10th weeks and 12th weeks of a pregnancy.
- Amniocentesis to test the amniotic fluid around the baby
or abnormal chromosomes and other substances such as
alpha fetoprotein. This test is first done between the
15th and 18th weeks of a pregnancy.
- Tests of DNA in a sample of tissue from the baby
(obtained, for example, by amniocentesis) to look for
problems in the genetic code.
- Percutaneous umbilical cord blood sampling, also called
PUBS, umbilical vein sampling, fetal blood sampling, or
cordocentesis. This procedure, similar to
amniocentesis, tests a sample of the baby's blood from
the vein in the umbilical cord. The blood can be tested
to look for chromosome problems, infection, blood
disorders, or other problems.
- Fetoscopic tissue sampling, which involves inserting a
tiny scope into the amniotic sac to test a sample of
the baby's skin for certain severe skin problems.
Your health care provider or counselor will discuss the
screening results with you. If there is a problem, they
will help you understand the problem. They will describe
your choices for prevention or treatment.
For support and information about genetic screening,
you can contact:
Disclaimer: This content is reviewed periodically and is subject to
change as new health information becomes available. The
information provided is intended to be informative and educational and is not a
replacement for professional medical evaluation, advice, diagnosis or
treatment by a healthcare professional.
HIA File WOM5240F.HTM Release 9.0/2006
Copyright © 2006 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.
Copyright © 2006 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.