Infant Mortality Related Definitions and Associated Formulas
LIVE BIRTH: The complete expulsion or extraction from its
mother of a product of human conception, irrespective of the duration of pregnancy,
which, after such expulsion or extraction, 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. (Definition recommended by World Health Organization in
1950). Heartbeats are to be distinguished from transient cardiac contractions;
respirations are to be distinguished from fleeting respiratory efforts or gasps.
AGE OF CHILD AT DEATH
INFANT DEATH: Death of a live born infant under one year of age.
NEONATAL DEATH: Death of a live born infant under 28 days of age.
PERINATAL DEATH: Death occurring during the perinatal period (i.e. to a live
born infant less than 28 days of age and a fetus that has passed the twentieth week
of gestation or weighs 350 grams or more).
POSTNEONATAL DEATH: Death of a live born infant 28-364 days of age.
MARITAL STATUS ON BIRTH CERTIFICATE:
UNMARRIED - a birth which occurs to a woman who has never been married or
who has been widowed or legally divorced from her husband in excess of 280 days.
MARRIED - a birth which occurs to a woman who has been married or was married
within 280 days from conception.
RATES:
INFANT MORTALITY RATE: Infant deaths per 1,000 annual live births(see animated
formulas).
CAUSE OF DEATH SPECIFIC RATE: Infant deaths due to a specific cause of death
per 100,000 annual live births.
AGE SPECIFIC RATE: Age specific infant deaths over total number of annual
live births per 1,000.
INDICATOR SPECIFIC RATE: Indicator specific infant deaths over indicator
specific annual live births per 1,000.
95% CONFIDENCE INTERVALS CALCULATION: r + 61.981*(r/n)
size="2">1/2
Where r = infant mortality rate, n = number of live births (denominator), and 61.981=1.96*(1000)1/2
When frequencies are less than 100 then 95% confidence intervals are calulated using
the formulas provided on pages 98-102 in the NCHS 2001 Birth Report a pdf document.
MATERNAL RISK FACTORS
MOTHERS RECEIVED PNC IN THE 1ST TRIMESTER: Mothers received prenatal care
in the 1st Trimester of pregnancy
MOTHERS DID NOT RECEIVE ANY PNC: Mother's received no prenatal care throughout
pregnancy
MOTHER'S LESS THAN 18 Births where the age of the mother was less than eighteen.
EDUCATION LESS THAN HIGH SCHOOL: Mother received less than 12 years of education.
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HOSPITAL LEVEL
LEVEL I
Level I hospitals provide services for uncomplicated deliveries and normal neonates.
They must have the capability to manage normal pregnant women and uncomplicated
labor and delivery of neonates who are at least 36 weeks of gestation with an anticipated
birth weight of greater than 2000 grams. These hospitals must be able to manage
an perinatal patient with acute or potentially life-threatening problems while preparing
for immediate transfer to a higher level hospital.
LEVEL II
Level II hospitals provide services for both the normal and selected high-risk obstetrical
and neonatal patients. This level of care includes the management of neonates who
are at least 32 weeks of gestation with an anticipated birth weight of at least
1500 grams. Neonates must be without acute distress or complex management requirements
and must not be in need of ventilatory support for more than six cumulative hours
nor require high frequency ventilation support. These hospitals manage no les than
an average of 500 deliveries annually, calculated over the previous three years.
LEVEL IIE+
In addition of Level II requirements, Level IIE+ hospitals provide services for
both normal and selected high-risk obstetrical and neonatal patients. This level
of neonatal care includes the management of neonates who are at least 30 weeks of
gestation with an anticipated birth weight of at least 1250 grams, as determined
by estimations based upon best professional judgment, ultrasound, and /or available
medical technology and instruments. Neonates are not in need of ventilatory support
for more than 24 cumulative hours and do not require high-frequency ventilation
support. These hospitals manage no less than an average of 1200 deliveries annually,
calculated over the previous three years.
LEVEL III HOSPITAL
Level III hospitals provides all aspects of perinatal care, including intensive
care and a range of continuously available, sub-specialty consultation as recommended
in the fourth edition of the Guidelines for Perinatal Care by the American Academy
of Pediatrics and the American College of Obstetricians and Gynecologists. In addition
to the Level II and IIE capabilities, Level III hospitals have the staffing and
technical capability to manage high-risk obstetric and complex neonatal patients,
including neonates requiring prolonged ventilatory support, surgical intervention,
or 24-hour availability of multispecialty management. Level III hospitals must have
no less than an average of 1500 deliveries annually, calculated over the previous
three years, or at least 125 neonate admissions who weigh less than 1500 grams each,
require ventilatory support, or require surgery.
REGIONAL PERINATAL CENTER
In addition to the Level III requirements for management of high-risk obstetric
and complex neonatal conditions, Regional Perinatal Center hospitals provide consultative,
outreach and support services to Level I, II, IIE and III hospitals in their region.
These hospitals manage no less than an average of 2000 deliveries annually, calculated
over the previous three years, or at least an average of 250 neonate admissions
who weigh less than 1500 grams each, require ventilatory support, or require surgery.
These hospitals must participate in residency programs for obstetrics, pediatrics
and/or family practice. Continuing education and outreach education programs must
be available to all referring hospitals, and physician-to-physician consultation
must be available 24 hours a days. Regional Perinatal Centers must provide a perinatal
transport system that operates 24 hours a day, seven days a week.
RATE CALCULATIONS WITH SMALL NUMBERS:
There are variations
in all statistics that are the result of chance. This characteristic is of particular
importance in classifications with small numbers of events where small variations
are proportionately large in relation to the base figure. As an example, small changes
in the number of deaths or births in small population areas or in the number of
deaths from uncommon causes could result in large changes in these crude rates.
For this reason, rates for counties with small populations or other small bases
should be used cautiously.
BIRTHWEIGHT:
VERY LOW BIRTHWEIGHT: Very low birthweight is a weight at birth which is
less than 1,500 grams (3 pounds, 4 ounces), regardless of the period of gestation.
LOW BIRTHWEIGHT: Low birthweight is a weight at birth which is less than
2,500 grams (5 pounds, 8 ounces), regardless of the period of gestation.
NORMAL BIRTHWEIGHT: Normal birthweight is a weight at birth which is greater
than 2,500 grams (5 pounds, 8 ounces), regardless of the period of gestation.
GRAMS WEIGHT CONVERSION CHART
500 grams or less = 1lb. 1 oz. or less
501 - 1,000 grams = 1 lb. 2 oz. - 2 lb. 3 oz.
1,001 - 1,500 grams = 2 lb. 4 oz. - 3 lb. 4 oz.
1,501 - 2,000 grams = 3 lb. 5 oz. - 4 lb. 6 oz.
2,001 - 2,500 grams = 4 lb. 7 oz. - 5 lb. 8 oz.
2,501 - 3,000 grams = 5 lb. 9 oz. - 6 lb. 9 oz.
3,000 - 3,500 grams = 6 lb. 10 oz. - 7 lb. 11 oz.
3,501 - 4,000 grams = 7 lb. 12 oz. - 8 lb. 13 oz.
4,001 - 4,500 grams = 8 lb. 14 oz. - 9 lb. 14 oz.
4,501 - 5,000 grams = 9 lb. 15 oz. - 11 lb. 0 oz.
5,001 grams or more = 11 lb. 1 oz - or more
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ADEQUACY OF PRENATAL CARE: KESSNER INDEX:
ADEQUATE*
Gestation (weeks)**** Number of Prenatal Visits
13 or less 1 or more or not stated
14-17 2 or more
18-21 3 or more
22-25 4 or more
26-29 5 or more
30-31 6 or more
32-33 7 or more
34-35 8 or more
36 or more 9 or more
INADEQUATE**
Gestation (weeks)**** Number of Prenatal Visits
14-21*** 0 or not stated
22-29 1 or less or not stated
30-31 2 or less or not stated
32-33 3 or less or not stated
34 or more 4 or less or not stated
INTERMEDIATE: All combinations other than specified above
* In addition to the specified number of visits indicated for adequate care, the
Interval to the first prenatal visit has to be 13 weeks or less (first trimester).
** In addition to the specified number of visits indicated for inadequate care,
all Women who started their prenatal care during the third trimester (28 weeks or
later) are considered inadequate.
*** For this gestation group, care is considered inadequate if the time of the first
visit is not stated.
**** When month and year are specified but day is missing, input 15 for day. Adequacy
categories are in accord with recommendations of American College of Obstetrics
and Gynecology and the World Health Organization.
ADEQUACY OF PRENATAL CARE: KOTELCHUCK INDEX:
The Kotelchuck Index, also called the Adequacy of Prenatal Care Utilization (APNCU)
Index, uses two crucial elements obtained from birth certificate data-when prenatal
care began (initiation) and the number of prenatal visits from when prenatal care
began until delivery (received services). The Kotelchuck index classifies the adequacy
of initiation as follows: pregnancy months 1 and 2, months 3 and 4, months 5 and
6, and months 7 to 9, with the underlying assumption that the earlier prenatal care
begins the better. To classify the adequacy of received services, the number of
prenatal visits is compared to the expected number of visits for the period between
when care began and the delivery date. The expected number of visits is based on
the American College of Obstetricians and Gynecologists prenatal care standards
for uncomplicated pregnancies and is adjusted for the gestational age when care
began and for the gestational age at delivery.
A ratio of observed to expected visits is calculated and grouped into four categories-Inadequate
(received less than 50% of expected visits), Intermediate (50%-79%), Adequate (80%-109%),
and Adequate Plus (110% or more). The final Kotelchuck index measure combines these
two dimensions into a single summary score. The profiles define adequate prenatal
care as a score of 80% or greater on the Kotelchuck Index, or the sum of the Adequate
and Adequate Plus categories.
The Kotelchuck Index does not measure the quality of prenatal care. It also depends
on the accuracy of the patient or health care provider's recall of the timing of
the first visit and the number of subsequent visits. The Kotelchuck Index uses recommendations
for low-risk pregnancies, and may not measure the adequacy of care for high-risk
women. The Kotelchuck Index is preferable to other indices because it includes a
category for women who receive more than the recommended amount of care (adequate
plus, or intensive utilization).
RACE: Information on race of the mother and father is reported
on birth and fetal death certificates, and the race of the decedent is reported
on death certificates. Fetal deaths are reported by race of mother. As of 1990,
Live Births are reported by race of mother instead of race of child. This change
allows South Carolina's birth data to be consistent with the National Center for
Health Statistics and other states throughout the United States. Race is reported
as White, Black Other, and Unknown.
ETHNICITY: Ethnicity is reported independently of race
on the birth certificate. Hispanic refers to those people whose origins are from
Spain, Mexico or the Spanish-speaking countries of Central and South America. Tabulation
categories are Hispanic, non-Hispanic, and unknown. If data is missing it is then
assigned to the unknown category.
RESIDENCE DATA: Data allocated to the place in South Carolina
where the person normally resided, regardless of where the event occurred.
COMPARABILITY: In order that disease classifications may
be consistent with advances in medical science and changes in diagnostic practice,
any system for categorizing causes of death must periodically be revised. Major
revisions in the International Classification of Diseases (ICD), by which causes
of death are classified, occur approximately every ten years, and each decennial
revision of the ICD has produced some break in comparability of cause of death statistics.
In South Carolina, the Sixth Revision of the ICD was used from 1949-1957; the Seventh
Revision for 1958-1968; the Eighth 1969-1978; and the Ninth Revision went 1979-1998;and
the Tenth Revision went into effect in 1999.
Prior to 1949, under the first five revisions, cause of death was selected on the
basis of priority tables for multiple causes, as set forth in The Manual For Joint
Causes of Death. Under the Sixth, Seventh, Eighth, and Ninth Revisions of the International
Lists, the cause selected for tabulation has been the "underlying" cause, defined
as the "disease or injury which initiated the train of morbid events, leading directly
to death." (ICDA, Eighth Revision, 1968, Vol. 1, page xxix).
The introduction of the concept of "underlying" cause in 1949, with the Sixth Revision,
resulted in a basic change in classification of death which seriously affects the
interpretation of mortality trends before and after 1949. The Seventh Revision was
essentially a clarification of the Sixth Revision, but the Eighth Revision introduced
some major modifications in classification lists and coding procedures. The Ninth
Revision also brought some major changes in classification and coding. However,
the Tenth Revision introduced some of the most dramatic changes so far.
In order to make valid comparisons of mortality by cause for events classified by
different revisions of the ICD, comparability ratios were developed. Comparability
ratios are computed by the National Center for Health Statistics from the results
of dual coding of certificates according to the old and the new procedures. Taking
the number of deaths classified to a given cause by the Tenth Revision and dividing
the result by the number of deaths classified to that cause by the Eighth Revision
derived the comparability ratios used with the Tenth Revision. Provisional comparability
ratios for the United States as a whole, based on the Ninth and Tenth Revisions,
have been developed for a limited number of causes published by the National Center
for Health Statistics.
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IMPLEMENTATION OF THE INTERNATIONAL CLASSIFICATION OF DISEASES (ICD
)10TH REVISION
The ICD is a classification system developed collaboratively between the World Health
Organization (WHO) and 10 international centers so that the medical terms reported
by physicians, medical examiners, and coroners on death certificates can be grouped
together for statistical purposes. ICD-10 replaces the ICD-9, used with 1979-1998
data.
The purpose of the ICD and of WHO sponsorship is to promote international comparability
in the collection, classification, processing and presentation of mortality statistics.
New revisions of the ICD are implemented periodically so that the classification
reflects advances in medical science.
ICD-10 affects the classification, processing, and presentation of mortality data.
Some titles have changed. The total number of categories has doubled as a result
of the addition or deletion of terms used to describe diseases or conditions. The
transfer of certain diseases from one section to another reflects new discoveries
and advances in knowledge on the nature or causes of particular diseases. The addition
of separate categories identifies specific diseases or particular complications
of diseases that are of growing interest. Additionally, the codes associated with
each title have been converted from numeric to alphanumeric entities. The ICD rules
for processing mortality data are generally similar but account for some changes
observed in mortality statistics.
HOW ICD-10 COMPARES TO ICD-9
The intent of developing new revisions is to incorporate changes in medical knowledge.
Compared with ICD-9, the ICD-10 has:
· expanded detail for many conditions (e.g., viral hepatitis has been expanded from
ICD-9 code 070, a single 3-digit category, to ICD-10 codes B15-B19, five 3-digit
categories)
· transferred conditions around the classification (e.g., hemorrhage has been moved
from the circulatory chapter to the symptoms and signs chapter)
· used alphanumeric codes instead of numeric codes (e.g., code for diabetes mellitus
was 250 in ICD-9 and is E10-E14 in ICD-10)
· modified coding rules (e.g., the "Old pneumonia, influenza, and maternal conditions"
and "Error and accidents in medical care" coding rules have been eliminated)
· modified the tabulations lists (e.g., the US' ICD-10 113-cause list replaces the
US' ICD-9 72-cause list)
Assistance in using the ICD-10 can be obtained by contacting the National Center
for Health Statistics, Data Dissemination Branch, 6525 Belcrest Road, Room 1064
Hyattsville, Maryland 20782-2003
(301) 458-4636 (voice) (301) 458-4027 (fax)
For more information about the ICD-10:
ICD-10 Web page at: www.cdc.gov/nchs/icd9.htm
Or see the National Center for Health Statistics(NCHS) Web site at:
www.cdc.gov/nchs/
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