For the first time in eight years, the number of births in the United States rose in 1998, by 2% from 1997, according to a report by the National Center for Health Statistics.1 Among women in their 30s, birthrates rose to their highest points in decades. The birthrate among teenagers, by contrast, continued its seven-year decline, decreasing 2%, to 51.1 births per 1,000 women aged 15-19; the rate among 15-17-year-olds reached a record low. While overall rates of preterm birth and low birth weight increased slightly in 1998, there also was an increase in the proportion of women who received prenatal care in the first trimester, continuing a nine-year trend.
The number of births in the United States rose to 3,941,553 in 1998, marking a 2% increase from 1997 and the first increase since 1990. The fertility rate rose 1% in 1998, to 65.6 births per 1,000 women aged 15-44, after decreasing 8% between 1990 and 1997. Non-Hispanic women are largely responsible for the change in the fertility rate: While rates fell among both non-Hispanic white and non-Hispanic black women between 1990 and 1997, they rose 1% (to 57.7 and 73.0 per 1,000, respectively) in 1998. By contrast, Hispanic women's fertility rate also has been declining, but did not make a turnaround in 1998: The rate decreased almost 2%, to 101.1 per 1,000--its lowest point in nine years.
The total fertility rate, or the estimated number of births that a hypothetical group of 1,000 women would have if during their childbearing years they experienced the age-specific birthrates recorded in a given year, increased 1% in 1998 to 2,059. This rate has increased 2% since 1995, but remains below replacement level (2,100 births per 1,000 women).
The birthrate among 15-19-year-olds fell 2% in 1998, to 51.1 births per 1,000 women. The rate has declined 18% since 1991, when it reached its peak of 62.1 per 1,000. The birthrate for 15-17-year-olds reached 30.4 per 1,000, a record low. Although the birthrate for 18-19-year-olds decreased 2% (to 82.0 per 1,000), the number of births increased 3% because the number of women in this age-group increased 5% from 1997 to 1998.
The decline in the teenage birthrate from 1997 to 1998 occurred among all racial and Hispanic-origin groups except for women of American Indian, Puerto Rican and "other" Hispanic descent. Between 1991 and 1998, the birthrate decreased 12% among Hispanic teenagers (to 93.6 per 1,000), 19% among non-Hispanic whites (to 35.2) and 26% among non-Hispanic blacks (to 88.2).
Teenage birthrates varied widely by state--from 24.4 per 1,000 women aged 15-19 in Vermont to 73.0 per 1,000 in Mississippi. The rates were lower in 1998 than in 1997 in all but nine states. When compared with 1991 rates, however, the 1998 rates were lower in all states and the District of Columbia. Thirteen states and the District of Columbia achieved declines of 20% or more between 1991 and 1998; five states achieved declines of 25% or more.
Birthrates for women in their 20s, who are in the peak reproductive years, have been relatively stable during the past two decades. They increased between 1997 and 1998--by 1%, to 111.2 per 1,000, among women aged 20-24 and by 2%, to 115.9 per 1,000, among those 25-29.
Unlike other age-groups, women in their 30s have had steadily increasing birthrates since the late 1970s; in 1998, the birthrate for these women reached its highest recorded level in three decades. In 1998, the birthrate for 30-34-year-olds increased 2%, to 87.4 per 1,000, and the rate for 35-39-year-olds increased 4%, to 37.4 per 1,000.
The birthrate for women aged 40-44 increased slightly between 1997 and 1998, from 7.1 to 7.3 per 1,000, but the number of births among this group increased 6%. Similarly, for women 45-49 years old, the birthrate was unchanged (at 0.4 per 1,000), but the number of births rose 9%, reaching the highest total recorded since 1968.
Though the birthrate among unmarried women has experienced a general decline in recent years, it increased 1% in 1998, to 44.3 per 1,000 unmarried women aged 15-44. Among unmarried women, those aged 18-19 and 20-24 have a higher birthrate (64.5 and 72.3 per 1,000, respectively) than other age-groups. The birthrate among unmarried Hispanic women is 90.1 per 1,000. The rates among unmarried white and black women of any ethnicity are 37.5 per 1,000 and 73.3 per 1,000, respectively.
The proportion of all births that occurred to unmarried women increased in 1998 to 33% from 32% in 1997. Sixty-nine percent of births to non-Hispanic black women were to unmarried women, as were 42% of births to Hispanic women and 22% of births to non-Hispanic white women.
Birthrates among unmarried teenagers have been declining since 1994 and reached 41.5 per 1,000 in 1998. Between 1994 and 1998, the rate declined 16%, to 27.0 per 1,000, among 15-17-year-olds and 8%, to 64.5 per 1,000, among 18-19-year-olds. Among unmarried black women aged 15-19, birthrates have declined 23% since 1991, to a 1998 rate of 83.4 per 1,000.
Pregnancy, Delivery and Birth Weight
The proportion of women who received prenatal care in the first trimester has increased 10% since 1989. In 1998, 83% of pregnant women began prenatal care in the first trimester; 4% received care only in the third trimester or not at all. Among women aged 15 and older in all racial groups, 15-19-year-olds were the most likely to receive late or no prenatal care--7%, compared with 3-5% of older women.
Thirteen percent of women who were pregnant in 1998 smoked cigarettes--a 34% decline since 1989, and a 2% decline since 1997. The proportion of women who smoked during pregnancy declined or remained the same among most racial and ethnic groups. For the fourth consecutive year, smoking among pregnant teenagers increased, by approximately 1%, to 18% of those aged 15-19.
The rate of cesarean delivery increased 2% in 1998, to 21.2 per 100 live births. The primary cesarean rate, or the rate of cesarean delivery among women who had had no previous cesarean, also increased 2%, to 14.9 per 100 live births. Non-Hispanic black women had a higher cesarean rate--22.4 per 100 live births--than did non-Hispanic white women and Hispanic women (21.2 and 20.6 per 100, respectively). The percentage increase in cesarean rates also was highest among black women.
The proportion of births that were preterm, or that occurred earlier than 37 weeks of gestation, increased to 11.6%, from 11.4% in 1997. The 1998 rate represents an overall increase of 9% since 1990. Among non-Hispanic white women, the rate of preterm births has increased 20% since 1989, partly because of increases in the rate of multiple births. The rate of preterm births among non-Hispanic black women remained at 17.6% in 1998, and the rate among Hispanic women rose slightly, from 11.2% to 11.4% between 1997 and 1998.
The proportion of infants who had a low birth weight (less than 2,500 g at birth) increased slightly, from 7.5% to 7.6%. This rate is as high as rates recorded in the 1970s, a result of the increases in the proportion of multiple births, which have a substantially higher association with low birth weight than singleton births. Among singletons, low birth weight decreased slightly, from 6.08% in 1997 to 6.05% in 1998. Although the incidence of low birth weight has risen 9% overall since 1989, it has increased less than 1% among singletons.--B. Brown
1. Ventura SJ et al., Births: final data for 1998, National Vital Statistics Reports, 2000, Vol. 48, No. 3.