Definitions of Measures Used in Birth-Related Modules
The information in the WISH birth-related modules is from Wisconsin resident birth certificate data. The Infant
Mortality module is based on both birth data and death certificate data.
Birth Order
The total number of live births to this mother, up to and including this birth.
Birthweight
The newborn’s weight is reported in grams, or pounds and ounces (converted to grams).
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Low birthweight: Infants weighing less than 2,500 grams (about 5.5 pounds) at birth.
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Very low birthweight: Infants weighing less than 1,500 grams (about 3.3 pounds) at birth.
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Extremely low birthweight: Infants weighing less than 1,000 grams (about 2.2 pounds) at birth.
Fertility Measures
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Birth Rate or Crude Birth Rate: The number of live births per 1,000 total population.
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General Fertility Rate: The number of live births per 1,000 females ages 15-44.
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Age-specific Fertility Rate: The number of live births per 1,000 females in an age group.
Gestational Age, Prematurity
Gestational age is based on the computed difference between the date of last normal menses and the date of the
infant’s birth. If the date of last normal menses is missing or the computed difference is less than 16 weeks or more
than 45 weeks, then the clinical estimate of gestational age reported by the attending physician is substituted. This
minimizes the number of births with unknown gestational age.
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Premature or preterm: Births are classified as premature (less than full term) if the gestational age was
less than 37 weeks. Births before 32 weeks of gestational age are "very preterm." Those 32 to 36 weeks are
"moderately preterm."
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Premature low birthweight: Births that have both a gestational age of less than 37 weeks and a birthweight of
less than 2,500 grams (about 5.5 pounds).
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Term low birthweight: Full-term births with low birthweight; that is, births that have a gestational age of
37 weeks or more and a weight at birth of less than 2,500 grams (about 5.5 pounds).
Infant Mortality
Infant mortality refers to deaths that occur within the first year of life.
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Infant mortality rate: The number of infant deaths per 1,000 live births during the year.
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Neonatal mortality: Infant deaths that occur before 28 days of age.
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Postneonatal mortality: Infant deaths that occur from 28 to 364 days of age.
Interval Since Last Delivery
The time between the mother’s last live birth and this delivery. This measure is computed from the birth date and the reported
month and year of last live birth. Unlike the Inter-Pregnancy Interval, it includes the gestation period of the current birth.
Multiple births have the same interval. Intervals of less than seven months or more than 30 years were coded as ‘missing.’
Inter-Pregnancy Interval
The time between the end of the mother’s last pregnancy and the estimated date of conception for this pregnancy. The reported
month and year of the mother’s last live birth is the best available measure of the end of the last pregnancy. The beginning
of this pregnancy is computed from the gestational age of this birth and the birth date.
Maternal Tobacco Use
Based on mother’s report of smoking during pregnancy (Yes/No indicator). Does not measure amount or duration of tobacco use
during pregnancy.
City of Milwaukee ZIP Codes
Birth Modules: ZIP code of mother’s mailing address, for those mothers reporting their residence is in the City of Milwaukee. WISH birth data
modules offer the 24 individual ZIP codes with at least 1,000 births since 1989. All other Milwaukee ZIP codes are
grouped into an ‘other’ category.
Infant Mortality Module: ZIP code of infant's residence at time of death, for those infants whose residence was in the City of
Milwaukee. This module offers the same ZIP code choices as in the birth modules.
Note: In previous editions of WISH, the following eight ZIP codes were grouped into one category: 53204, 53205, 53206, 53208, 53212,
53215, 53216, and 53233. All other ZIP codes reported by City of Milwaukee residents were grouped into a second ‘other’
category.
Mother’s Race and Ethnicity
Six groups based on first reported race of mother, and whether or not mother reported Hispanic/Latina ethnicity. The groups are:
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White (Non-Hispanic)
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Black (Non-Hispanic)
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American Indian (Non-Hispanic)
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Hispanic
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Laotian / Hmong (Non-Hispanic)
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Other (Non-Hispanic, almost entirely Asian)
Newborn Transferred to Another Hospital
Whether the infant was transferred from the birth hospital to a different hospital.
The birth hospital reports whether the infant was ‘treated in an NICU or transferred to another hospital’ and also reports the
name of the transfer/NICU hospital, which may be itself. If this item is checked on the birth report and the transfer/NICU
hospital is not the birth hospital, then this is coded ‘yes.’
NICU Utilization
Whether the infant was treated in a Level 3 neonatal intensive care unit, either in the birth hospital or in a hospital to
which the infant was transferred from the birth hospital.
The birth hospital reports whether the infant was ‘treated in an NICU or transferred to another hospital’ and also reports the
name of the transfer/NICU hospital, which may be itself. If this item is checked on the birth report and the birth hospital
has a Level 3 NICU, then NICU Utilization is ‘yes.’ If this item is checked and the birth hospital reports transferring the
infant to another hospital and that hospital has a Level 3 NICU, then NICU Utilization is also coded as ‘yes.’
Number of Previous Pregnancies
The number of previous pregnancies for this mother, regardless of outcome (live birth, miscarriage, other outcome).
Single or Multiple Birth
Plurality: the number of fetuses in this pregnancy (single, twins, triplets, etc.). Not all may result in live births.
Prenatal Care, Adequacy of Prenatal Care
Two common measures of adequate prenatal care are the ‘Kessner Index’ and the ‘Kotelchuck Index,’ both of which
consider the month care began and the number of visits, taking into account the gestational age at delivery.
The Kessner Index of Prenatal Care Adequacy uses the following classifications for a full-term birth:
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Adequate: Initiation in the first trimester with nine or more visits.
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Intermediate: Initiation in the first trimester with five to eight visits, or initiation in the second trimester with
five or more visits.
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Inadequate: Initiation in the second trimester with one to four visits, or initiation in the third trimester with one
or more visits.
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None: No prenatal care.
The number of visits is adjusted for preterm births.
The Kotelchuck Adequacy of Prenatal Care Utilization Index also takes into account the month that prenatal care began
and the number of prenatal visits, and adjusts for gestational age. It includes categories for adequate, intermediate, and
inadequate levels of prenatal care utilization. The number of prenatal visits is compared to the expected number for
gestational age, based on the American College of Obstetricians and Gynecologists prenatal care standards for uncomplicated
pregnancies.
Teen Births
Births to women less than 20 years of age are considered teen births. This group is often divided into older teens (18-19) and
younger teens (15-17). Very few births occur to females under age 15 and they are included in counts and rates for the ‘under
18’ and ‘under 20’ groups.
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Teen birth rate: The number of births to mothers less than 20 years of age per 1,000 females ages 15-19.
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Last Revised: July 18, 2010
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