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Small Area Investigations

Although the California Birth Defects Monitoring Program does not routinely analyze data from small areas such as zip codes or census tracts, we have developed a protocol to respond to specific community concerns about the environment.

The protocol looks for hallmarks seen when an environmental agent has been found to cause birth defects:

  • Dramatic increase in a specific condition
  • Characteristic pattern of defects
  • Common exposure.

The protocol will uncover major birth defects problems, but generally cannot determine if environmental conditions are causing birth defects. For this, sizeable studies with accurate exposure information are needed.

Steps for evaluating small areas include:

  • Comparing the area’s overall birth defects rate to county and registry-wide rates.
  • Examining rates of 7 specific birth defects which are common and likely to be uniformly diagnosed statewide: heart defects, chromosome abnormalities, pyloric stenosis, oral clefts, limb defects, neural tube defects and intestinal atresias.
  • Evaluating rates of other conditions if past scientific studies suggest possible links to the environmental exposure of concern.
  • Reviewing cases to look for recurring patterns of defects or other similarities.