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Section 2. Natality - Narrative

Center for Health Statistics and Vital Records      

Oregon Vital Statistics Annual Report 1995, Volume 1 

 

Natality

INDICATORS OF BIRTHING TRENDS

In 1995, Oregon recorded 42,715 resident births. Though there were 883 more resident births than in 1994, the crude birth rate remained unchanged at 13.6 per 1,000 population (the lowest rate since 1935). The fertility rate increased slightly to 62.3 per 1000 women 15-44. [Table 1-2]. Oregon's crude birth rate (the number of babies born divided by the total state population) peaked in 1947 at 25.4 per 1,000 population. For the last quarter century, however, Oregon's rates have held in the mid-teens, ranging from the 1994-1995 low of 13.6 to a high of 16.9 in 1970. Except for the period between 1976 and 1981, Oregon's crude birth rate has remained lower than the national rate. In 1995, Oregon's rate was 8.1 percent lower than the nation's (13.6 vs. 14.8). 1 [Figure 1-1].

AGE-SPECIFIC BIRTH AND FERTILITY RATES

The fertility rate is based on the number of births per 1,000 women age 15-44. Unlike the crude rate, it considers only those women who are of childbearing age, making it a more precise measurement of changes in behavioral patterns. Oregon's 1995 fertility rate increased 2 percent from the 1994 rate ( see sidebar). Age-specific birth rates increased in every age group. The largest increase was among women 40-44 (7%) followed by women age 25-29 (5%). Table 2-2 shows the change in age-specific birth rates over time. The birth rate for teens declined, with minor fluctuations, over a 36-year period that ended in 1986. It then rose annually until 1991, reaching 55.2 per 1,000 15- to 19-year-olds, the highest rate since 1971. The teen birth rate then began another decline. Between 1991 and 1994, it fell 7 percent to a level below that recorded in 1990. In 1995, the rate increased slightly to 52.2 per 1,000. The youngest mothers were 12 years old, the oldest 54. (For more discussion, see the Teen Pregnancy Section of this report.)

MARITAL STATUS OF MOTHER

Unmarried mothers as a group have poorer birth outcomes than married women. They generally have a greater proportion of babies with low birthweight and low Apgar scores than do their married counterparts. Their infants are also more likely to require neonatal intensive care, to have congenital anomalies, or to die before age 1. Over the last 20 years, the percentage of births to unmarried mothers has tripled in Oregon. [Figure 2-2].


In 1995, 28.9 percent of all Oregon births were to unmarried mothers, an all-time high. [Table 1-2]. Although Oregon has consistently had lower unmarried rates than the U.S., the gap between the two rates has narrowed in recent years. In 1983, the U.S. rate was 26 percent higher than the Oregon rate. In 1995, Oregon's rate was 10 percent lower. 1 [Figure 2-2]. Among women giving birth in 1995, the percentage who were unmarried varied widely by ethnic and racial group (see sidebar). Non-Hispanic African American mothers had the highest percentage of unmarried mothers (70.7%), followed by non-Hispanic American Indian mothers (53.7%). Non-Hispanic Chinese mothers were least likely to be unmarried (5.0%). Younger mothers were very likely to be single, since Oregon law prohibits marriage under age 17. Although 74 percent of mothers 15-19 were unmarried, this percentage dropped by nearly 50 percent for women 20-24, and by another 50 percent for women 25-29. Further decreases occurred in the two older age groups: Mothers 40-44 were least likely to be unmarried (12.4%), while 12.8 percent of mothers age 35-39 were unmarried. [Table 2-3]. Ten of Oregon's 36 counties had significantly higher rates of unmarried mothers to total births compared to the state average. [Table 2-7]. Wheeler had the highest rate (409.1 per 1,000), followed by Coos (396.3 per 1,000). Six Oregon counties had unmarried rates significantly lower than the state average, with the lowest rate in Wallowa County (134.3). A county's unmarried rate should be viewed in part as a function of its own specific population mix. Younger mothers, minority mothers, and mothers with a lower level of education often have higher unmarried rates. Variations in population composition involving any of these factors will likely result in significant differences between counties.

MATERNAL RACE/ETHNICITY

Because precise population data are available only for Census years, it is not possible to calculate birth rates by racial and ethnic group, only the number of births. Beginning in 1981 and continuing through 1988, Hispanic ethnicity was classified as a race category on the birth certificate. Since 1989, there has been a separate question about Hispanic ethnicity. These changes are associated with some of the increase in reporting of births to Hispanic mothers. An increased willingness to self-report minority affiliation may also be occurring among all groups. The number of resident births to non-Hispanic white women decreased 4 percent since 1989. There have also been decreases in the number of births to non-Hispanic American Indian mothers (12%) and non-Hispanic African American mothers (4%). [Figure 2-3]. The number of births to mothers of Hispanic ethnicity increased 124 percent since 1989. [Table 2-4]. In two Oregon counties, over 40 percent of residents giving birth in 1995 identified themselves as Hispanic: Malheur (42.4%) and Hood River (41.3%). [Table 2-6]. However, the 340 births to Hispanic residents of these counties represented less than one percent of the state's total births and 6.8 percent of the state's births to Hispanic mothers.


LOW BIRTHWEIGHT


National Healthy People 2000 Objective


Reduce low birthweight to an incidence of no more than 5.0 percent of live births.
Percentage of Oregon low birthweight births 1995: 5.5%


Of the thousands of infants born every year, not all thrive and become healthy adults. Birth outcome may be measured by several indicators, but the best predictor of an infant's future health is its birthweight. The low birthweight rate is the proportion of infants who weigh less than 2,500 grams (5.5 pounds) at birth. These infants are more likely to need extensive medical treatment, and some may have lifelong disabling conditions.

The National Public Health Service has set a year 2000 objective to reduce the percentage of low birthweight infants to 5 percent. The 1995 percentage of low birthweight infants in Oregon was slightly above the year 2000 objective at 5.5 percent. In 1995, there were 2,345 low birthweight babies born to Oregon mothers, a rate of 54.9 per 1,000 live births. Although this is slightly higher than the 1994 figure of 53.0, the rate has fluctuated little over the last 15 years. [Table 1-6; Figure 2-4]. Oregon's low birthweight rates are typically 25 percent lower than those of the U.S. In 1987, this difference had dropped to 22 percent. [Tables 1-5 and 1-6]. In 1995, Oregon's rate was 25 percent lower than the nation's. Since 1992, both the state and national low birthweight rates have increased. Major factors contributing to the risk of having a low birthweight baby are multiple gestation births, tobacco use, and chronic hypertension. Other factors include: non-white race, mother's age (younger than 18 or older than 35), lack of prenatal care, low income, single marital status, a previous fetal or infant death, low maternal education, and short spacing between births. 2 Low birthweight is the major predictor of infant death, which in turn is a fundamental measure of the health of a population. (For more information, see the Perinatal and Infant Death section to be published in Volume 2 of the Oregon Vital Statistics Annual Report.)

TOBACCO USE


Oregon Benchmark for the year 2000


Percentage of infants whose mothers (self-reported) used tobacco during pregnancy.
Year 2000 Goal: 15.0 percent
1995: 17.8 percent


Women who smoke when pregnant have a far higher incidence of low birthweight babies than nonsmokers. 3 In 1995, the difference was nearly 2 to 1 (90.4 per 1,000 live births vs. 46.6). Nearly one out of five mothers (17.8%) reported using tobacco during pregnancy, a rate virtually unchanged in the last three years. Unmarried mothers were over three times more likely to smoke than married mothers (35.3% vs. 10.8%). Smoking trends by marital status differed according to age. The rates for married mothers declined with age. Among unmarried mothers, the rate was highest in the 30-34 year old age group. The lowest smoking prevalence rates were among married women age 40 and older. Smoking prevalence as reported on birth certificates varied among racial and ethnic groups. (When reviewing these prevalence rates, note that data gathering procedures may not have been uniform. Consequently, the figures may not reflect the extent to which smoking rates varied among these groups. It is possible that physicians, practitioners, and birth certificate clerks may have been more diligent in investigating smoking practices for racial/ethnic groups considered at higher risk for delivery of low birthweight infants. This may be true for other behavioral risk factors as well.) Non-Hispanic Hawaiians and non-Hispanic American Indians had the highest reported smoking rates: 33.3 percent for each group. Non-Hispanic Chinese women reported no tobacco use during pregnancy. [Table 2-20].

ALCOHOL USE

Oregon Benchmark for the year 2000


Percentage of infants whose mothers (self-reported) used alcohol during pregnancy.
Year 2000 Goal: 2.0 percent
1995: 2.5 percent


Used during pregnancy, alcohol can cause deformity, mental retardation, and other severe developmental problems. 4 Low birthweight rates were 1.3 times higher for mothers who consumed alcohol (71.9 per 1,000 vs. 53.6). Based on self-reporting from birth certificates, 2.5 percent of Oregon mothers (1,071 women) drank alcohol during pregnancy in 1995. This represents a 47 percent decline from 1990, when 4.7 percent of mothers reported alcohol use. Non-Hispanic American Indian women were most likely to have reported using alcohol during pregnancy (7.3%), followed by non-Hispanic African American women ( 4.0%). [Table 2-20]. Non-Hispanic Chinese women reported no alcohol use during pregnancy.

PRENATAL CARE

Oregon Benchmark for the year 2000


Percentage of infants whose mothers received early prenatal care (first trimester).
Year 2000 Goal: 90.0 percent
1995: 78.5 percent


Public health services and private care providers seek to minimize the risk of death and disability, and to reduce costs associated with low birthweight infants by providing comprehensive prenatal care services. There are two preferred ways to measure prenatal care: 1) "inadequate prenatal care," defined as no care until the third trimester or fewer than five prenatal visits; and 2) "early care," defined as care beginning during the first three months of pregnancy, regardless of the number of total prenatal visits. Early or first trimester care has been adopted as an Oregon Benchmark with a goal to ensure that 100 percent of pregnant women begin prenatal care in the first three months. Just under 6 percent of 1995 mothers giving birth received inadequate care. They were 2.3 times more likely to give birth to a low birthweight child. In 1995, 21.5 percent of mothers did not receive first trimester care. They were 1.2 times more likely to have a low birthweight child. [Table 2-12]. In 1995, the number of women who received early care totaled 33,534, a slight increase from 1994. The percentage (78.5%), however, was slightly lower than in 1994. [Figure 2-6]. The proportion who received no prenatal care or who received third trimester care also increased. [Figure 2-7]. Women under 15 were least likely to have obtained first trimester care and those 35-39 were most likely (43.3% vs. 85.6%). [Table 2-15].


The mother's level of education was closely related to patterns of prenatal care. [Table 2-11]. Women with less than a high school education were least likely to obtain adequate prenatal care; those who had college degrees or higher were most likely to have adequate care.

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Thirteen of Oregon's 36 counties had first trimester care rates significantly lower than the statewide rate: Coos, Crook, Curry, Jackson, Jefferson, Josephine, Klamath, Lake, Lane, Malheur, Marion, Morrow, and Umatilla. Eight counties had rates significantly higher than the statewide rate: Baker, Benton, Clackamas, Douglas, Deschutes, Polk, Union and Washington. [Table 2-13].

BIRTH ATTENDANT

A major shift over the past few years has been the increasing prevalence of births attended by certified nurse midwives (CNM). In 1995, the percentage of CNM-attended deliveries was 12.6 percent, an increase of 14 percent over 1994, and over twice the percent in 1988 (5.9%). Most in-hospital births (84.3%) were delivered by MDs, a slightly lower rate than in 1994. Certified nurse midwives delivered 12.5 percent of in-hospital births, a 12 percent increase over 1994. [Table 2-23].

OUT-OF-HOSPITAL BIRTHS

In 1991, Oregon had a higher proportion of out-of-hospital births (2.2%) than any other state. In 1995, the Oregon figure remained at 2.2 percent of Oregon occurrence births. Outcomes have generally been positive for out-of-hospital births, which may reflect the screening process used by out-of-hospital birth providers. The mothers who delivered out-of-hospital, were generally not high-risk patients. In 1995, only 25 infants born out of hospital in Oregon had low birthweights (2.6%). However, fourteen (1.4%) were reported to have a congenital anomaly, which is nearly identical to the percentage for in-hospital births. The type of attendant varies by birth setting. Licensed direct entry midwives, a new category of attendant in 1994, were predominant in out-of-hospital births, delivering nearly one-third (32.2%) of these births in 1995. Licensed direct entry midwives are lay midwives who have volunteered for state licensure to provide natality care for Oregon women. Lay midwives delivered 24.3 percent of out-of-hospital births. In addition, CNMs delivered one in six babies (16.5%), and naturopathic physicians delivered one in nine babies (10.8%).

SOURCE OF PAYMENT Primary source of payment for delivery is noted on Oregon birth certificates under four categories: 1) private insurance, 2) self-pay [no insurance], 3) public insurance [Medicaid/Oregon Health Plan], and 4) other [other public insurance]. The specific type of private insurance coverage or public health payer source is not defined. Multiple payment sources can be indicated. Slightly more than one percent of mothers received delivery payments were from multiple sources. The majority of deliveries in Oregon were paid for by private insurance companies (57.9%), but the percentage increased in the last two years (see sidebar). [Table 2-17 ]. More than one-third of Oregon resident births (35.5%) were paid for by Medicaid (e.g., Oregon Health Plan). This percentage has been increasing since 1990, partly because of Oregon Medicaid's adoption of less restrictive income requirements for pregnant women, based on a federal mandate. Implemented on April 1, 1990, this action enabled more births to qualify for public insurance. In 1989, by contrast, public insurance programs paid for just over one-fourth of total births. Delivery costs were more likely to be paid for by public insurance if the mother was not married or under 18 years of age. Among mothers 25 or older, unmarried women were over four times more likely than married women to report payment by public insurance (63.2% vs. 15.0%). [Table 2-17].

REFERENCES

  1. Rosenberg HM, Ventura SJ, Mauer JD, et al. Births and Deaths: United States 1995. Monthly Vital Statistics Report; vol. 45, no. 3, supp. 2. Hyattsville, Maryland: National Center for Health Statistics. 1996.
  2. National Center for Health Statistics. Healthy People 2000 Review, 1995-96. Hyattsville, Maryland: Public Health Service. 1996.
  3. Tobacco and Oregonians, A Legacy of Illness and Death. Center for Health Statistics, Health Services, Oregon Department of Human Resources. Portland, Oregon. 1992.
  4. Alcohol and Drugs in Oregon, 1989. Center for Health Statistics, Health Services, Oregon Department of Human Resources. Portland, Oregon. 1992.

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