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About Birth Defects Data

about birth defects

Data on birth defects on the Tracking Network is provided by the Iowa Registry for Congenital and Inherited Disorders. The Iowa Registry for Congenital and Inherited Disorders was established in 1983 through the joint efforts of the University of Iowa, the Iowa Department of Public Health, and the Iowa Department of Human Services.

This page provides general information about the birth defects data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

What do these data tell us:

  • The prevalence rate of select birth defects in Iowa counties and statewide by year, race/ethnicity of mother, and age of mother.
  • If a segment of a population is at higher risk for select birth defects.

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How can we use these data:

  • To inform the public about select birth defects.
  • For program planning and evaluation by state and local partners.
  • Allow for consistent and rapid method for calculating and displaying prevalence at selected geographical areas.
  • Allow for a better understanding of spatial and temporal patterns of selected birth defects.

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What can these data not tell us:

  • These data cannot tell us what causes birth defects, or factors that lead to changes in birth defect rates.
  • Iowa Public Health Tracking birth defects measures are prevalence rates of 12 selected birth defects per 10,000 live births.
  • The incidence of birth defects would be the ideal measure for birth defects, but it cannot be determined as it requires information that is difficult to determine, such as the number of conceptions and the number of cases "lost" through fetal deaths (i.e., miscarriages, terminations).

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What is the source of the data:

  • Birth defects data on the Iowa Public Health Tracking portal is provided by the Iowa Registry for Congenital and Inherited Disorders (IRCID). The IRCID was established in 1983 through the joint efforts of the University of Iowa, the Iowa Department of Public Health, and the Iowa Department of Human Services.
  • State vital records data for the number of live births, by year.

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What time period of data is available:

  • The Iowa Public Health Tracking portal displays birth defect data from the year 2000 through the most recent year of data available.
  • There is usually a three or four-year lag period before birth defects data are available on the Iowa Public Health Tracking portal.

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How birth defects are identified:

  • The Iowa Registry for Congenital and Inherited Disorders performs active surveillance, which means trained abstractors review medical records to make sure all reported potential cases meet rigorous case definitions established by both Iowa and national experts.
  • Only live births are included on the Iowa Public Health Tracking portal. Iowa does not publish data that includes stillbirths or pregnancy terminations.
  • The Birth Defects Program uses multiple data sources to help ensure that all cases are identified. In addition to the primary case finding source of hospital medical records, they use birth certificates, death certificates, and newborn screening data for case finding.
  • Quality control and data evaluation efforts are performed annually, including an assessment of completeness, accuracy and timeliness. Because cases may be abstracted through one year of age and then subsequent quality control analysis must be performed, there is a 2-3 year data reporting lag.
  • These data include information about babies born in Iowa with certain health conditions (Anencephaly, Spina Bifida, Hypoplastic Left Heart Syndrome, Tetralogy of Fallot, Transposition of the Great Arteries, Cleft Lip, Cleft Palate, Hypospadias, Gastroschisis, Upper Limb Reductions, Lower Limb Reductions, Trisomy 21) diagnosed within the first year of life.

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What is the difference between a number and a prevalence rate? How would I use them?

Number:

  • The number indicates the total number of birth defects, not the number of people with birth defects.
  • To protect an individual's privacy, counts of 5 or less are suppressed.
  • Due to the small number of birth defects only the prevalence rates are displayed.

Prevalence Rate:

  • If you want to understand the probability or what is the underlying risk in a population, then use a rate.
  • In our analysis a prevalence rate is calculated using the number of events as the numerator (the number of birth defects during a period of time) divided by the number of people at risk as the denominator (the number of live births during the same period of time). This fraction is then multiplied by 10,000 to provide a more recognizable value.
  • To protect an individual's privacy, prevalence rates based on counts of 5 or less are suppressed.

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The limitations of the data:

  • Iowa Public Health Tracking birth defects measures are aggregated to include 5 years of data. Because birth defect rates are based on only five years of aggregated data, the rates may be suppressed or vary considerably when compared with data from other states that have been collecting birth defects information for a longer time period.
  • Ideally, incidence rates would be used instead of birth prevalence to measure birth defects occurrence. The numerator of the incidence would be the number of new cases of birth defect A in an area and time period and the denominator would be the number of conceptions at risk of developing birth defect A in that area and time period. Because the both the number of conceptions is unknown and the number of cases “lost” through spontaneous abortions (as well as terminations and later fetal losses depending on the source of ascertainment for the specific surveillance system), incidence cannot be calculated. Birth prevalence is the only appropriate measure that can be reported for birth defects occurrence.

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Where can I find more technical information about the data?

More detailed documentation of the birth defects data can be found in the following documents:

Indicator Profiles

Birth Defects Prevalence
Trisomy 21 Prevalence

Descriptive Metadata

Birth Defects Prevalence

Contact Us to learn more about birth defects data, or any of the measures displayed on the Iowa Public Health Tracking Portal.

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