Pregnancy and Childbirth Among Females Aged 10–19 Years — United States, 2007–2010

Stephanie J. Ventura, MA

Brady E. Hamilton, PhD

T.J. Mathews, MS

National Center for Health Statistics, CDC

Corresponding author: Stephanie J. Ventura, Division of Vital Statistics, National Center for Health Statistics, CDC. Telephone: 301-458-4547; E-mail: sventura@cdc.gov.

Introduction

Pregnancy and childbirth among females aged <20 years have been the subject of long-standing concern among the public, the public health community, and policy makers (1–3). Teenagers who give birth are much more likely than older women to deliver a low birthweight or preterm infant, and their babies are at higher risk for dying in infancy (4–6). The annual public costs associated with births among teenage girls are an estimated $10.9 billion (7). According to the 2006–2010 National Survey of Family Growth (NSFG), an estimated 77% of births to teenagers aged 15–19 years were unintended (8).

The 2010 U.S. birth rate among females aged 15–19 was 34.2 births per 1,000. This is a 10% decrease from 2009 (37.9) and an 18% decrease from 2007 (41.5) (9). A long-term decrease that began in 1991 was continuous except for a brief increase during 2005–2007; the birth rate among females aged 15–19 years decreased by 45% from 1991 (61.8 per 1,000) to 2010 (9,10). An analysis found that if the 1991 birth rates for females aged 15–19 years had remained the same during 1992–2010, an additional 3.4 million births would have occurred among women aged 15–19 years in the United States (11). Significant decreases in birth rates for females aged 15–19 years occurred among all race and Hispanic ethnicity groups from 2007 to 2010, including non-Hispanic whites, non-Hispanic blacks, American Indian/Alaska Natives (AI/ANs), Asians or Pacific Islanders (A/PIs), and Hispanics. Rates also decreased for certain Hispanic groups, including those of Mexican and Puerto Rican origin. Despite the widespread decreases, disparities persist (9,11), and the U.S. birth rate for females aged 15–19 years remains one of the highest among industrialized countries (12).

This report is part of the second CDC Health Disparities and Inequalities Report (CHDIR) and updates information presented in the first CHDIR (13). The 2011 CHDIR (14) was the first CDC report to assess disparities across a wide range of diseases, behavioral risk factors, environmental exposures, social determinants, and health-care access. The topics presented in this report are based on criteria that are described in the 2013 CHDIR Introduction (15). The purposes of this pregnancy and childbirth analysis and discussion are to highlight and raise awareness of differences in the characteristics of females aged <20 years (including 10–14, 15–19, 15–17, and 18–19 years) who become pregnant and give birth and to prompt actions to reduce these disparities.

Methods

To analyze recent trends and variations in birth rates and pregnancy rates by selected characteristics among females aged 10–19 years, CDC examined final 2007 and 2010 natality data from the National Vital Statistics System (NVSS) and comparable data for earlier years. Characteristics analyzed varied by rate calculated and included four age groups (10–14, 15–19, 15–17, and 18–19 years), race, ethnicity, and state, including the District of Columbia. Household income and educational attainment were not analyzed because income information is not collected on the birth certificate, and data on educational attainment are collected in different ways across the states. Thus, national data on educational attainment are not available.

Data by maternal race and Hispanic ethnicity are based on information reported by the mother during the birth registration process. Race and ethnicity are reported separately on birth certificates, and persons of Hispanic origin might be of any race. Race categories are consistent with the 1977 Office of Management and Budget standards (4,9). In 2010, a total of 38 states and the District of Columbia reported multiple-race data that were bridged to the single-race categories for comparability with other states (9). Population estimates with bridged-race categories for the rates in this report were produced under a collaborative arrangement with the U.S. Census Bureau. Rates for 2010 are based on the 2010 U.S. census, and rates for earlier years are based on intercensal estimates (9,16,17). Rates are not shown when the number of births in a given group is <20 or, for specified Hispanic groups, if <50 females are in the denominator in the census year 2010 or <75,000 females are in the denominator for all other years.

Birth rates were calculated as the number of births to females per 1,000 female population in the specified age, race, and Hispanic origin group. The rate in 2010 was compared with 2007 and previously published rates for 1991. The change in birth rate over time (i.e., relative difference) was calculated by subtracting the rate at the end of the period from the rate at the beginning of the period, dividing the difference by the rate at the beginning of the period, and then multiplying by 100. Percentage change for birth rates in 2007 and 2010 was assessed for statistical significance by using the z test at the 95% confidence level (18). Disparities were measured as the deviations from a referent category rate. Absolute difference was measured as the simple difference between a population group estimate and the estimate for its respective reference group. The relative difference, a percentage, was calculated by dividing the absolute difference by the value in the referent category and multiplying by 100.

Pregnancy rates are presented by pregnancy outcome (live births, induced abortions, and fetal losses), race, and Hispanic ethnicity. Data on live births are based on complete counts of births provided by every state to CDC through the Vital Statistics Cooperative Program of NVSS (18). Abortion estimates are from abortion surveillance information on the characteristics of women who have abortions collected from most states by CDC; these estimates are adjusted to national totals by the Guttmacher Institute (19–22). Fetal loss rates are derived from pregnancy history data collected from several cycles of the National Survey of Family Growth (NSFG) conducted by CDC (22,23). Data regarding pregnancy are not as current, complete, or comprehensive as NVSS data regarding births. The most recent pregnancy estimates that include data on live births, induced abortions, and fetal losses are for 2008 (22).

Results

In 2010, birth rates for females aged 15–19 years varied considerably by race and Hispanic origin (Table 1). The rates for Hispanics (55.7 births per 1,000 females aged 15–19 years) and non-Hispanic blacks (51.5 births) were approximately five times the rate for A/PIs (10.9 births) and approximately twice the rate for non-Hispanic whites (23.5 births). The rate for AI/ANs aged 15–19 years was intermediate (38.7 births per 1,000 females aged 15–19 years). Rates varied considerably across specified Hispanic groups. The rate in 2010 was highest for "other" Hispanics aged 15–19 years (65.4 births per 1,000), followed by Mexican (55.5 births), Puerto Rican (43.7 births), and Cuban (24.4 births).

From 2007 to 2010, birth rates for females aged 15–19 years decreased significantly for all race groups and for nearly all specified Hispanic groups (Table 1). Decreases for females aged 15–19 years ranged from 14% to 17% for non-Hispanic whites and non-Hispanic blacks, respectively, to 32% for Mexicans. Among females aged 15–17 years, significant decreases from 2007 to 2010 ranged from 16% to 21% among non-Hispanic whites and non-Hispanic blacks, respectively, to 35% for Mexicans. Among females aged 18–19 years, decreases ranged from 16% to 19% among non-Hispanic whites and non-Hispanic blacks, respectively, to 30% for Mexicans. The trends cannot be reliably analyzed for Cubans because the numbers of births were too few and for Puerto Ricans aged 18–19 years because the estimated number of females in this age group in 2007 was <75,000.

In 2010, birth rates among females aged 15–19 years by state ranged from <20 per 1,000 females aged 15–19 years in four states (New Hampshire [15.7 births], Massachusetts [17.2 births], Vermont [17.9 births], and Connecticut [18.7 births]) to 50 per 1,000 or more in five states (Oklahoma [50.4 births], Texas [52.2 births], Arkansas [52.5 births], New Mexico [53.0 births], and Mississippi [55.0 births]) (Table 2) (9,11). From 2007 to 2010, rates decreased significantly in all but three states (Montana, North Dakota, and West Virginia). Decreases in 16 states ranged from 20% to 30%.

The pregnancy rate for teenagers aged 15–19 years was 69.8 per 1,000 in 2008. The rates by pregnancy outcome were 40.2 for live births, 17.8 for induced abortions, and 11.8 for fetal losses; substantial demographic differences were found in these rates (Table 3) (22). Within each age group from 10–14 years through 18–19 years, pregnancy rates among non-Hispanic black and Hispanic females were two to three times higher than rates for non-Hispanic white females (22). The rate decreased by 3% from 71.9 pregnancies per 1,000 females aged 15–19 years in 2007 to 69.8 per 1,000 in 2008 (Table 3) (22). Pregnancy rates have decreased for females aged 10–14, 15–17, and 18–19 years and for non-Hispanic white, non-Hispanic black, and Hispanic females aged 15–19, 15–17, and 18–19 years.

Discussion

In 2010, the U.S. birth rate for females aged 15–19 years had decreased 45% since the 1991 peak (from 61.8 in 1991 to 34.2 in 2010) (9–11) Trends in birth rates by age and by race and Hispanic ethnicity group indictae that the long-term reductions since 1991 have been experienced by all population groups but were somewhat greater for certain groups (9–11). The birth rate for females aged 10–14 years decreased 71%, from 1.4 per 1,000 in 1991 to 0.4 in 2010; rates for those aged 10–14 years decreased approximately 60% in each racial and Hispanic origin group. The birth rate for all females aged 15–17 years decreased more by approximately half, from 38.6 per 1,000 in 1991 to 17.3 in 2010; decreases ranged from 53% for Hispanics aged 15–17 years to 68%–69% for non-Hispanic blacks and A/PIs (9). The overall decrease in the rate for females aged 18–19 years was 38%, from 94.0 per 1,000 in 1991 to 58.2 in 2010; decreases ranged from 40% and 42% for non-Hispanic white and Hispanic females aged 18–19 years, to 47% to 56% for non-Hispanic black, AI/AN, and A/PI females aged 18–19 years (9,11).

The recent decreases in birth rates have coincided with decreases in pregnancy, abortion, and fetal loss rates among females aged 10–14, 15–19, 15–17, and 18–19 years (22). The pregnancy rate in 2008 for females aged 15–19 years was the lowest ever in the more than 3 decades for which a national series of rates is available (22,24). However, disparities in rates by race and ethnicity have changed little since 1990.

The findings in this report and a recent overview of state-level birth rates both have documented the persistent large variation across states (Table 2) (11). Birth rates for females aged 15–19 years tend to be highest in the South and Southwest and lowest in the Northeast and upper Midwest, a pattern that has persisted for many years (25,26). Some of the variation among states reflects differences in the racial/ethnic composition of the population within states (26). More in-depth analysis of trends and variations in state-specific rates by race and Hispanic ethnicity is forthcoming with the recent availability of revised intercensal population estimates (9).

Limitations

The findings in this report are subject to at least four limitations. First, a full assessment of disparities in childbearing among females aged 10–19 years depends on having complete data on patterns of pregnancies in this age group. The downward trend since 1991 in abortions among females aged <20 years has been more substantial than the downward trend among births. For example, the abortion rate for females aged 15–19 years decreased 52% from 1991 to 2008, whereas the birth rate decreased 35% during this period. A full understanding of patterns in pregnancy among females aged <20 years requires timely data on abortions and fetal losses as well as live births. The birth rate decreased 15% during 2008–2010. The extent to which the downward trends in abortions continued from 2008 to 2010 is not yet known. Second, the components of the pregnancy estimates and pregnancy outcome estimates vary in quality and completeness. Birth data are complete counts, whereas the abortion estimates are based on incomplete surveillance and survey data, and the fetal loss estimates are based on pregnancy histories collected from survey data (9,19,21,22,24). Third, data on teen pregnancy are available only for the largest population groups: non-Hispanic white, non-Hispanic black, and Hispanic. The necessary information on abortions and fetal losses is not available for other race groups (i.e., A/PI or AI/AN) or for specific Hispanic groups (19–21,23,24). Finally, evaluating trends and disparities in state-specific birth rates depends on having accurate population estimates by age, race, and Hispanic ethnicity. Recently released revised intercensal population estimates provide detailed data at the state and county level by single year of age. In years going forward, these newly released population estimates and estimates from the American Community Survey for Hispanic population groups will be used to improve the precision of the estimated rates.

Conclusion

Data from the 2006–2010 NSFG conducted by CDC have shown little change in the proportion of males and females aged 15–19 years who have ever had sex (27). This finding was corroborated in data released from the 2011 Youth Risk Behavior Surveillance report (28). For the period from 2002 to 2006–2010, NSFG found a significant decrease only among non-Hispanic black females aged 15–19 years in the percentage of those who were sexually experienced; changes for other groups were not significant. However, virtually all race and Hispanic origin groups have experienced significant long-term decreases in the proportion of those who are sexually experienced (27). The 2006–2010 NSFG also documents increased use, compared with 2002 and earlier rounds of the NSFG, of contraception at first intercourse and increased use of two methods of contraception (i.e., condoms and hormonal methods) among sexually active male and female teenagers (27). The recent NSFG data show fewer differences than in previous years by race and Hispanic origin in overall contraceptive use at first and last sex, largely reflecting increasing condom use among all groups (27). Various other factors contribute to the observed variations in teenage birth rates, including differences in education and income and in attitudes among teenagers toward pregnancy and childbearing; these factors in turn affect sexual activity and contraceptive use (27). The impact of strong and consistent pregnancy prevention messages and programs directed toward teenagers aged <20 years has been credited with the long-term decline in teenage birth rates. These programs were implemented in the aftermath of rapid increases in teenage birth rates from 1986 to 1991. Studies have shown that to be effective, programs must be designed to meet the specific needs of different groups of teenagers, and continually evaluating interventions and programs to assess their effectiveness is important (1–3,29–32).

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