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Lesson 2: Case Description
In April 1991, three babies with
anencephaly were born in a Brownsville, Texas,
hospital within 36 hours. The three babies died soon after birth. Since this
was an unusual cluster, it got the notice of the health workers in the
area. Doctors in the Texas State Department of Health asked epidemiologists
from the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, to
help them look into the problem. See headlines.
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CLUSTER.
A group of cases close in time and place. For example, if
illness occurred in several students after they ate in the
cafeteria, these illnesses would be called "a cluster
of cases." |
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 Background on Brownsville,
Texas in Cameron County
Brownsville is the most southern city in Texas. It is in Cameron
County on the Mexico border. In 1989, over 80% of the people were
Hispanic and over 40% of the families had low incomes. In 1990, 270,524
people lived in Cameron County.
When these cases occurred in Cameron County in 1991, little was known
about what causes NTDs like anencephaly. It was known that, in
the United States, NTDs are most common among Hispanics and least common in African
Americans. The birth defects are also more common in families with less money.
Community members thought the birth defect problems could be related to pollution from
pesticide use and assembly plant industries along the Mexico/U.S. border.
To tell the class:
A birth defect happens while a baby is developing inside the mother.
At that time, the baby is fragile and defenseless. Many things that
the mother eats, drinks, and breathes her baby also eats, drinks, and
breathes. Because the baby is small and changing so fast, it is more
sensitive than the mother. Many birth defects happen in the first
three months (first trimester) of pregnancy. Neural tube defects like
anencephaly happen in the first month of pregnancy, before most women know
they are pregnant.
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Small
Group
Activity Print the
graphic of the pregnant woman and make a
transparency and copies of the page for groups of 3 or 4 students. Divide the class
into groups and have the students brainstorm a list of risk factors for the
neural tube birth defects. See definition of risk factors in box. Have group
members write or draw the factors they think could have occurred, then discuss these
ideas. When the groups are finished, record the class ideas on the overhead
transparency, post each group's papers on the wall, and discuss. |
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RISK FACTOR.
Personal behavior or lifestyle, an environmental exposure,
or a family trait that might cause a health problem. |
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Factors that have been linked to birth defects and other problems for
babies include: genetics, toxic chemicals, drugs, certain medicines (for example
epilepsy medication, and Accutane® for acne), illness in mothers (such as
diabetes), mother's age, environmental factors, physical injury during pregnancy,
contaminated water, alcohol, tobacco, inhalants, poor nutrition, and some infectious
diseases, viruses, and bacteria.
 To read: In the United States, 1 of every 1,000
babies is born with a neural tube defect. The rates are lowest on the West Coast,
and highest in the Appalachian region of the U.S. Rates were highest in the
U.S. in the
1930's at 5 per 1,000 births. In certain parts of China, the rate of neural
tube defects is 5-6 per 1,000 births. In Mexico, the rate is 3-4 per 1,000 births.
Group Discussion
What are some possible
reasons rates of birth defects vary by region of the country in the U.S., in different
parts of the world, and over time?
Eating patterns, genetics, racial/ethnic characteristics, environmental factors, and
poverty may affect rates of birth defects. In summary, the rates of birth defects
may depend on individual, location, and time of exposure.
Link to Lesson 3: Scientific
Method
Date: September 1, 2006
Content source: National Center on Birth Defects and Developmental
Disabilities
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