Definitions and Associated Formulas
ANIMATED FORMULAS
This link shows formulas used to calculate rates with examples.
MOTHER'S HEALTH AND LIFESTYLE VARIABLES
This link lists all Mother's Health and Lifestyle Variables.
RESIDENCE DATA: Data allocated to the place in South Carolina
where the person normally resided, regardless of where the event occurred.
MATERNAL DEATH: Death of a woman whose cause of death is
assigned to Complications of Pregnancy, Childbirth, and Puerperium. If death occurred
more than 42 days after termination of pregnancy, the death is not considered to
be pregnancy-related.
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.
VERY LOW BIRTH WEIGHT: Very low birth weight is a weight
at birth which is less than 1,500 grams (3 pounds, 4 ounces), regardless of the
period of gestation.
LOW BIRTH WEIGHT: Low birth weight is a weight at birth
which is less than 2,500 grams (5 pounds, 8 ounces), regardless of the period of
gestation.
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:
CRUDE BIRTH RATE: Annual live births over total population
AGE SPECIFIC RATE: age specific live births over age specific female population
FERTILITY RATE: Annual live births over population of women 15-44 year of
age (see animated formulas)
95% CONFIDENCE INTERVALS CALCULATION: r + 61.981*(r/n)1/2
Where r = live birth rate, n = number of live births or population denominator,
and 61.981=1.96*(1000)1/2
When frequencies are less than 100 then 95% confidence intervals are calculated
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
EDUCATION LESS THAN HIGH SCHOOL: Mother received less than 12 years of education.
USED ALCOHOL DURING PREGNANCY: Mother reported using alcohol during pregnancy.
SMOKED DURING PREGNANCY: Mother reported smoking during pregnancy.
METHOD OF DELIVERY
PRIMARY C-SECTION DELIVERY: Delivery by cesarean section where no previous
cesarean section had been performed.
VAGINAL BIRTH AFTER PREVIOUS C-SECTION DELIVERY: Delivery by vaginal birth
where previous cesarean section had been performed.
REPEAT C-SECTION DELIVERY: Delivery by cesarean section where previous cesarean
section had been performed.
OBSTETRIC PROCEDURES
LIVE BIRTHS WITH AMNIOCENTESIS: Surgical transabdominal perforation of the
uterus to obtain amniotic fluid to be used in the detection of genetic disorders,
fetal abnormalities, and fetal lung maturity.
LIVE BIRTHS WITH ELECTRONIC FETAL MONITORING: Monitoring with external devices
applied to the maternal abdomen or with internal devices with an electrode attached
to the fetal scalp and a catheter through the cervix into the uterus, to detect
and record fetal heart tones and uterine contractions.
LIVE BIRTHS WITH INDUCTION OF LABOR: The initiation of uterine contractions
before the spontaneous onset of labor by medical and/or surgical means for the purpose
of delivery.
LIVE BIRTHS WITH STIMULATION OF LABOR: Augmentation of previously established
labor by use of oxytocin.
LIVE BIRTHS WITH TOCOLYSIS: Use of medications to inhibit preterm uterine
contractions to extend the length of pregnancy and, therefore, avoid a preterm birth.
LIVE BIRTHS WITH ULTRASOUND: Visualization of the fetus and the placenta
by means of sound waves amount of oxygen reaching fetal tissues).
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).
INTER-PREGNANCY INTERNAL: The time period (in months)
between the conception date of this pregnancy and the date of last pregnancy outcome
(could be live birth, abortion, fetal death, etc).
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. Other race group includes asian, pacific islander,
and native americans.
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.
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.
POPULATION DATA: With the exception of population data
by race and population data for selected age groups of teens, the 2000 Census data,
provided by the Office of Research and Statistics (South Carolina Budget and Control
Board), were used to calculate the rates in this report. Population data by race
and for selected age groups were modified.
POPULATION DATA BY RACE: The U.S. Census Bureau Population
data contains data for both "multiple race", and single race categories. This presents
problems for calculating vital statistical rates. The following methodology was
developed jointly by Office of Research and Statistics, South Carolina State Budget
and Control Board and the Division of Biostatistics and Health GIS, Public Health
Statistics and Information Services, SCDHEC.
The populations of these two race categories were allocated to the standard single
race categories by age, gender and county. This allocation was based on the proportional
distribution of the population of the standard single race categories within each
of these age, gender, county groups.
POPULATION DATA FOR SELECTED AGE GROUPS: For inter-census
years, ORS provides estimated population data for South Carolina by age for five-year
age groups. It is assumed that the population within each of these age categories
is distributed uniformly through out the age interval. Based on this assumption,
the population for females 14-17, 15-17 and 18-19 years is derived, consecutively,
as follows - (20% of the female population 10-14 years plus 60% of the female population
15-19 years), (60% of the female population 15-19), and (40% of the female population
15-19). Pregnancy data for these teenagers are published annually in the South
Carolina Vital and Morbidity Statistics reports and also in the South
Carolina Teen Pregnancy Data Book(s).
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
Changes in the 2004 birth certificates
In 2004, a revised certificate of live birth was implemented. This may affect comparisons
of variables to previous years. Some of the questions were removed from the birth
certificates while some new ones were added. This is why some indicators of the
Mother's Health and Lifestyle, such as ultrasound, amniocentesis, etc.., are no
longer available in year 2004 and thereafter. With some questions, the way of describing
the question or the layout of the questionnaire were different, thus it is possible
that the same variable in the new birth record has a subtle difference from the
old one. If user obtains statistics of both year 2004 and previous years, they should
be cautious in interpreting the trend since it may not be a real trend but due to
a different definition or data quality of the same variable.
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