Source of Birth Data

Information on Colorado births is collected from the Certificate of Live Birth. Data items are presented as reported on the certificate. Completeness and accuracy of items on the birth certificate may vary by facility and year. Data for all births that occurred within the state of Colorado, resident and nonresident, are collected; however, at this time, CoHID only reports data for Colorado resident births. Resident births are births to those individuals who reported being residents of Colorado, even if the birth occurred to residents while outside of Colorado. Interstate agreements allow for the exchange of vital information about births to Colorado residents that occurred in other states. County-specific data are for births reported as occurring for residents of those counties.

Clarifications on Birth Data

Race/Ethnicity

In 1989 the National Center for Health Statistics adopted the use of race/ethnicity of the mother for birth data, rather than race/ethnicity of the child, as a standard classification. Since that time Colorado birth statistics have also been presented by race/ethnicity of the mother.

Race and ethnic backgrounds are determined by responses to race and Hispanic origin questions on the birth certificate. In order to best approximate the race and ethnic groups found among the Colorado population, and to follow standard measures of race, CoHID presents the following race categories: all, white, black, Asian, and American Indian. Used together with ethnicity (all, Hispanic, and non-Hispanic), most combinations of race and ethnicity found in Colorado can be constructed.

The unknown category is used to classify those cases where race was either stated as unknown or left blank on the certificate.

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Gestational Age

A birth that is less than 37 weeks gestation is defined as preterm. Preterm birth is a major cause of infant mortality. Preterm babies are also at greater risk of neurodevelopmental and respiratory disorders.

CoHID presents the clinical estimate of gestational age at birth, which is determined by the physician attending the birth and is based on physical examination of the infant.

Prenatal Care

Early entry into prenatal care can promote healthier births by detecting and managing pre-existing medical conditions and providing health behavior advice.

"Early entry into prenatal care" is care started in the first trimester (first 3 months) of pregnancy. "Late prenatal care" has been interpreted in two different ways. The more traditional definition, used by the National Center for Health Statistics, includes care started in the third trimester, care at delivery only, and no care. More recently, however, a new definition of "late prenatal care," based on the Health Status Indicator for the Year 2000. U.S. Department of Health and Human Services, was introduced as care beginning later than the first trimester.

The Health Status Indicator for the Year 2010 is to increase to at least 90 percent the proportion of all pregnant women who receive prenatal care in the first trimester.

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Multiple (Plural) Births

According to the National Center for Health Statistics (NCHS), multiple births are at greater risk than singletons of being born too early and too small and, accordingly, of not surviving the first year of life.

NCHS has reported that much of the increase in multiple births has been related to the increased use of fertility-enhancing techniques. Birth certificate data do not indicate whether a birth resulted from the use of fertility-enhancing techniques.

Birth Weight

By definition, a newborn weighing less than 2,500 grams (less than 5lb 9oz) is considered a low weight birth. A newborn weighing less than 1,500 grams (less than 3lb 5oz) is considered a very low weight birth. According to the National Center for Health Statistics, infants born at low weight are at much greater risk for long-term morbidity and early death.

Studies have identified a number of risk factors for low birth weight, including insufficient weight gain during pregnancy, maternal smoking, younger and older maternal age, low socioeconomic status, low level of mother's education, late entry into prenatal care, and substance abuse during pregnancy. Multiple births are most likely to be born too small.

Birth Rates and Fertility Rates

A birth rate is the number of births that occur within a certain population (or area) over a specified time period in relation to the total population of the area. Specifically, it is the number of births per 1,000 total population.

A fertility rate is the measure of fertility (births) among the females of a population. The general fertility rate measures the fertility among women of childbearing age, defined as ages 15-44. The general fertility rate is the total number of births per 1,000 females ages 15-44 in the population. An age-specific fertility rate is the number of births for a specified age group per 1,000 females in the age group.

Because birth rates and fertility rates are derived using population estimates, these rates are sensitive to changes in the methods used for estimating populations. The fertility rates derived from CoHID for some age groups may vary from those published in other reports due to the changes in the methods used for calculating the population estimates.

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Data Quality

Many quality control edits are built into the data reporting and compilation system on CoHID. However, as with all large, complex data sets, completeness and accuracy of reporting may vary by individual data item. Birth data are presented as reported on birth certificates. The unknown category is used to classify those cases where the value or characteristic was either stated as unknown or left blank on the certificate.

Confidentiality

Birth records are confidential in accordance with Colorado statutes (Section 25-2-117). To maintain confidentiality and prevent the identification of an individual, the results of any search returning fewer than three events will be suppressed.

Definitions

Birth Rate: The number of births that occur within a certain population or geographical area, over a specified time period, in relation to the total population of the group or area. Specifically, the number of births per 1,000 total population.

Birth to Unmarried Woman: A mother is considered to be unmarried if she was not married at the time of conception and did not marry at any time between conception and delivery. Common-law marriages are recognized as legal marriages in Colorado.

Birth Weight: The first weight of the fetus or newborn obtained after birth. This weight preferably is measured within the 1st hour of life, before a significant postnatal weight loss has occurred.

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Fertility Rate (age-specific): The number of births for a specified age group of females within a certain population or area per 1,000 total females in the age group.

General Fertility Rate: A measure of the fertility among women of childbearing age, defined as ages 15-44. Specifically, the number of births to all females over a certain time period per 1,000 females aged 15-44 in the population.

Gestation age: Completed weeks of pregnancy from the first day of the mother's last normal menstrual period.

Live Birth: The complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of pregnancy, which, after such separation, breathes, or shows any other evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached; each product of such a birth is considered live born. Birth data on CoHID are for live births only.

Low Weight Birth: Birth weight of less than 2,500 grams (less than 5lb 9oz). A very low weight birth is less than 1500 grams (less than 3lb 5oz).

Multiple Birth: More than one child born resulting from a single pregnancy. Also called plural birth.

Perinatal: Pertaining to or occurring in the period shortly before and after birth. There are several commonly used definitions for the perinatal period, extending from 20 weeks of gestation to 4 weeks after birth.

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Postterm: Births occurring at a gestational age greater than or equal to 42 weeks (>293 days).

Premature Birth: Birth occurring prior to 37 completed weeks of gestation, but after that stage of viability at about 20 weeks gestation.

Prenatal: Existing or occurring before birth.

Prenatal Care: Medical care during pregnancy before birth.

Prenatal Visits: The number of visits made to a physician or other health care provider during the prenatal period for medical supervision of a pregnancy.

Preterm: Births occurring prior to 37 completed weeks of gestation (<259 days).

Singleton: Single birth.

Term: Births occurring between 37 and 41 completed weeks of gestation (259-293 days).

Trimester: A 3-month period of time. First trimester care, for example, refers to care initiated in the 1st three months of pregnancy.

For more information on birth data not contained on CoHID, or for data prior to 1990, please contact the Health Statistics and Evaluation Branch of the Colorado Department of Public Health and Environment at 303-692-2160.

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