Past studies of birth defects have been hampered by limited perspective. Epidemiologic research—looking at occurrence patterns in a population—assumes that all individuals are equally susceptible to environmental exposures. Genetic studies—looking at biologic variation between individuals— tend to ignore environmental influences. In either case, misclassification of conditions (for example, lumping together defects with different origins) can mask links between birth defects and their causes.
The California Birth Defects Monitoring Program is at the forefront of a new era of birth defects research, combining both genetic and environmental information. Recent studies take advantage of genetic discoveries accompanying the Human Genome Project as well as technologic advances in measuring exposures. When combined with in-depth interview data, biologic testing often clarifies associations. Some of the techniques we use include:
|DNA testing. Study subjects are often asked to swab the inside of their mouths to painlessly collect cells for genetic analysis. These results help supplement exposure information gained from interviews.|
|Biomarkers. Saved blood samples from prenatal or newborn screening tests can be analyzed for substances that indicate the presence of infection or other environmental exposures at the time of fetal development|
|Refined classification. Genetic tests can help distinguish different types of birth defects, guiding the search for clues. For example, determining whether the extra chromosome seen in Down syndrome came from the egg or sperm can focus attention to exposures in either the mother or father.|