Estimated Time:  15 minutes

Small Group Activity

Divide the students into groups of 3 or 4.   Give the groups a copy of the scientific method.  Using the scientific method below have the groups outline a plan to find the cause of these birth defects.  Then have group members discuss their plans with the class. 

Steps of the scientific method
1. Name the problem or question
2. Form an educated guess (hypothesis) of the cause of the problem and make predictions based upon the hypothesis
3. Test your hypothesis by doing an experiment or study (with proper controls)
4. Check and interpret your results
5. Report your results to the scientific community

Epidemiologists use different types of studies.  One type is observational.   This type watches people over a certain amount of time to see of their health habits or traits relate to whether or not they get certain diseases. The researcher does not change a person's habits or give them any treatments. They watch to see what people do and determine whether or not they get a disease. There are two types of observational studies: prospective and retrospective.  A prospective study looks at the characteristics of a group of people and then follows them to see who gets a disease and who doesn't.  This can take a while.  If we found 100 young women and found out about some of their lifestyle and genetic characteristics, and then followed them for five years to see which ones have babies with birth defects it would be an observational, prospective study.  

A retrospective study looks at the people who have the disease or health problem and tries to determine what characteristics they have that may have contributed to them getting the disease. For example, if we found 100 women who had babies with a birth defect and asked them questions about the types of food they ate, or where they worked, this would be an example of a retrospective study.  

A case-control study is a type of retrospective study. Epidemiologists use the information that they have collected to guess (form a hypothesis) about what caused the health problem. Then they try to determine who has the health problem or disease, and who does not. A case is the occurrence of the health problem or disease in a person. A control is the absence of the health problem or disease in a person.  Researchers compare the cases and controls by talking to the people who have the health problem or disease as well as the people who do not have the health problem or disease to see what is different between them. 

After an observational study suggests what may be the cause of the health problem or disease and how they plan to treat it, then researchers do another type of study. This is a testing (experimental) study.  One group of people is given something to take (exposed group), and another group is not given that substance (non-exposed group).  Then the scientists see if the group that received the substance has different results than the group that did not receive the substance.  

When doing a study, scientists must follow certain rules to treat people fairly:
    1)  The first principle of medicine is to DO NO HARM!   Scientists must not test something on people that is already known to be harmful.
    2)  If a treatment is proven helpful, the study must be stopped and the treatment must be offered to everyone who could be helped by it.
    3)  If during the study the results begin to show harm, the study must be stopped.

For example, many studies have already shown that smoking and alcohol can hurt babies before they are born.  Since this is known, it would be wrong for a study to ask pregnant women to smoke or drink alcohol to see how their babies turn out. 

Teachers:  Link for a larger copy of this chart.

Epidemiologists begin studies with a complete version of the scientific method.  Below are the 10 steps they use to conduct an investigation.  In real life, several steps may be done at the same time, or in a different order.  

Next, we will look at the methods used by epidemiologists to learn about the cause of the cluster of birth defects in the Texas babies.

Link to Lesson 4:  Scientific Investigation

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This page was last updated Wednesday, January 28, 2004

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Centers for Disease Control and Prevention
National Center on Birth Defects and Developmental Disabilities

The National Center on Birth Defects and Developmental Disabilities (NCBDDD) promotes the health of babies, children, and adults, and enhance the potential for full, productive living.  Our work includes identifying the causes of birth defects and developmental disabilities, helping children to develop and reach their full potential, and promoting health and well-being among people of all ages with disabilities.