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A birth defect is an abnormality of structure, function, or metabolism (body chemistry) present at birth that results in physical or mental disabilities or, sometimes, even death.

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Did You Know?
About 120,000 babies (1 in 33) in the United States are born each year with birth defects. Source: March of Dimes 2013

In the United States, about 3% or one out of every 33 babies is born with a birth defect. Most birth defects are thought to be caused by a complex mix of genetic, behavioral, and environmental factors, although for many birth defects, exactly how these factors work together is unclear.

The causes of between 70 and 80 percent of birth defects are unknown. Sometimes they just happen with no clear cause. Sometimes the cause of a birth defect is determined after the baby is born.

It is not clear how many birth defects are related to environmental exposures, such as chemicals, ionizing radiation, drugs, and infections. Researchers are looking at a wide variety of environmental exposures and risk factors as possible causes.

Birth defects data reported on this website are obtained from the Massachusetts Center for Birth Defects Research and Prevention within the Massachusetts Department of Public Health/Bureau of Family Health and Nutrition. This center collects birth defects data from birthing hospitals and other medical facilities throughout Massachusetts.

Twelve birth defects are included on the EPHT network. They include: anencephaly, spina bifida (without anencephaly), hypoplastic left heart syndrome, tetralogy of Fallot, transposition of the great arteries (vessels), cleft lip with cleft palate, cleft lip without cleft palate, cleft palate without cleft lip, hypospadias, gastroschisis, limb deficiencies, and trisomy 21. Definitions of these birth defects can be found in the Birth Defect Descriptions tab and glossary.

Data Considerations

When reviewing and interpreting birth defects data, it is important to take into consideration the following:

  • Prevalence estimates are based on the residential location of the mother at the time of the child’s diagnosis.
  • Defects related to early fetal deaths (gestational age < 20 weeks) and/or terminations are not included in prevalence estimates. Furthermore, defects that are not diagnosed at birth, that do not need hospitalization or that are diagnosed after age one may be underreported.
  • When looking at a smaller geographic area, such as a county, cell suppression rules may be applied to protect the privacy of a child with a birth defect and their family.
  • Counts and prevalence estimates may differ slightly from those contained in other publications. These differences may be due to file updates, differences in calculation methods (such as grouping ages differently or rounding off numbers at different points in calculations), and updates or differences in population estimates.

For additional information, please read the FAQ.

Available Data on Birth Defects

Use the Explore Maps & Tables link on this page to access the following measures for birth defects in your community. The most current available data will be shown. Be sure to check the site periodically as new data are added each year. To protect privacy, no information is shown that could identify an individual.

  • Annual state birth defects prevalence per 10,000 live births by birth defect
  • 5-year birth defects prevalence per 10,000 live births for Massachusetts counties and statewide by birth defect
More About the Data
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