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The NBDPS is a research study. Research involves collecting information in an organized way to answer specific questions about a certain topic. The collected information is then analyzed to answer the questions that were asked. Because the study is done in a structured and systematic way, we have some proof that the answers we find are true. More specifically, the NBDPS is an observational, population-based, case-control study. That’s a mouthful! Let’s take the terms one at a time.

• The study is observational because it simply looks at what is already going on. It does not test medicines or treatments or ask people to do anything differently. In the NBDPS, interviewers interview the families and send out the cheek cell kits, and the researchers analyze the information from the interviews and kits.
• The NBDPS is population-based because it looks at all people with a certain health outcome who live in a certain area. That area could be a state or a number of counties. One of the important things to watch is whether the number of people with a given outcome in the study area changes over time.
• The NBDPS is a case-control study because information is collected from both people who have a health issue (cases) and people who do not have the health issue (controls). The controls might also be called the comparison group. In the NBDPS, controls are selected randomly from the birth certificate records of birth hospitals.

What are the components of the study?
The study has two parts: a telephone interview and collection of cheek cells from family members. Interviewers talk to women who have had pregnancies or babies affected by birth defects, as well as mothers of babies with no birth defects.

The interviewers ask women about their pregnancy experience and health. There is no way to recreate the many events and exposures that happen during pregnancy—only women can give us this information. After the interview, the study researchers send small brushes to each family for collection of cheek cells from mothers, fathers, and babies. Cheek cells contain genetic material called DNA, which we use to examine the role that genetic factors play in the development of a baby.