CENTER FOR
HEALTH
STATISTICS
MINNESOTA VITALSIG S
MINNESOTA DEPARTMENT
OF HEALTH
August 2005 Vol. 1, No. 5
Births to Older Mothers
The number and rate of births to older mothers in the United States has increased substantially since the late 1970s
(National Center for Health Statistics, 2005). Since 1978, birth rates for women 35-39 and 40-44 years old have
more than doubled in the U.S. Researchers have proposed that these trends are the result of delayed childbirth due
to mothers’ careers and education and perhaps a reduction in medical risk in later childbearing years. This report
examines trends in births to older women (35 years of age and older) in Minnesota including the number and rate of
births, race, and prenatal care. In addition, birth outcomes including preterm births (less than 37 weeks gestation),
low birth weight (less than 2500 grams), and infant mortality rates (deaths per 1,000 live births) are also discussed.
Birth certificate data for older mothers were obtained for 1980-2003. Infant death rates were obtained from a linked
birth and death database for 1980-2002.
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
35-39
20
02
20
00
19
98
19
96
19
94
19
92
19
90
19
88
19
86
19
84
40-44
19
82
19
80
Rate
Figure 1: Birth Rate* by Selected Age Groups
Minnesota, 1980-2003
*per 1,000 population in that age group
Overview
The number of older women giving birth in Minnesota has increased dramatically over the years. Figure 1 indicates
that since 1980, birth rates have more than doubled for both 35-39 and 40-44 year olds. In 1980, the birth rate for
35-39 year old women was 20.0 per 1,000 females. Currently, the birth rate for women in this age group is 46.9 per
1,000 females 35-39 years old. Although the birth rate is considerably lower for the women in the 40-44 year old
age group, the rate has also more than doubled from 4.0 per 1,000 in 1980 to 8.5 per 1,000 in 2003. Birth rates for
women 45 and over are not reported due to small numbers.
August 2005
1
The actual number of births also demonstrates the growth in births to older mothers. In 2003, 10,657 births were to
women ages 35 and over which is greater than three times the number of births in 1980 for this same age group
(2,922). The percent of total births to women 35 and over increased from 4.3 percent in 1980 to 15.2 percent of
total births in 2003.
Table 1: Births by Age of Mother Minnesota (Selected Years)
Age Group
35-39
40-44
45 and Over
35 and Over Total
1980
Number of Births by Year
1985
1990
1995
2,485
408
29
2,922
3,804
432
35
4,271
5,587
785
44
6,416
7,109
1,166
56
8,331
8,764
1,786
107
10,657
Total
67,836
67,402
67,982
63,246
70,053
4.3%
6.3%
9.4%
13.2%
15.2%
% of Births to Women 35+
2003
First Time Mothers
Women are delaying the age at which they have their first child. 10.2 percent of women who had their first baby in
1980 were 35 years old and over. By 2003 this had increased to 22.2 percent (Figure 2), the highest since 1980.
Figure 2: Percent of First Births to Women 35 Years and Older
Minnesota, 1980-2003
25.0
22.2
Percent
20.0
15.0
10.2
10.0
5.0
0.0
1980
1983
1986
1989
1992
1995
1998
2001 2003
Race and Ethnicity
Most recent data indicate that the percent of births to women ages 35 and older has increased among Whites,
African Americans, American Indians, and Hispanics. The most dramatic of these increases are births to Whites
and African Americans. Currently, the percent of births to White and African American mothers 35 years and older
is over three times higher than 1980-85 figures. In the most recent time period, the percent of births to mothers 35
years and older has decreased for mothers of Asian descent though the 1999-2003 figures are higher than 1980-1984
figures.
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2
Figure 3: Percent of Births by Race and Age 35 Years and Older
by Minnesota, Selected Years
Percent
1980-1985
18.0
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
15.9
1990-1994
14.1
1999-2003
12.6
10.9
10.1
9.5
7.0
6.1
5.1
3.0
White
African
American
5.8
5.5
7.2
3.9
American Indian
Asian
Hispanic*
*Hispanic data was not available for the 1980-1985 time period.
Prematurity and Low Birth Weight
Preterm delivery and low birth weight are closely associated with poor birth outcomes. Data indicate that the
incidence of low birth weight births (under 2,500 grams) has increased among 35-39, 40-44, and 45 years and older
age groups. Most notable is the increase in low birth weight births among those 45 years and older where the
percent of low birth weight in this age group is more than three times the percent in 1980-84. Also, while the
percent of low birth weight births is lower among 35-39 and 40-44 year olds, the percent of low birth weight births
has continued to increase from previous years reporting.
Percent
Figure 4: Percent Low Birth Weight* Babies by Selected Age Groups
Minnesota, Selected Years
16.0
14.7
14.0
12.0
10.0
8.0
10.1
8.2
7.2
5.2
6.0
5.9
7.0
6.8
6.3**
4.5
4.0
2.0
0.0
1980-1984
35-39 Yrs
1990-1994
40-44 Yrs
1999-2003
45 Yrs and Over
*Less than 2500 grams
**Overall percent of low birth weight babies for Minnesota in 2003
Prematurity (37 weeks or less gestation) is an increasing concern for women giving birth at 35 years and older.
While the overall percent of premature births in 2003 was 9.9 percent, the percent of premature births for women 45
years and older is 17.6 percent. Figure 5 shows that for older women, the risk of having an infant
prematurely increases with age.
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3
Figure 5: Percent Premature* Births by Age of Mother
Minnesota, Selected Years
20.0
17.6
Percent
15.0
7.8
10.0
13.6
12.0
9.4
9.0
10.7
10.5
11.9
9.9**
5.0
0.0
1980-1984
35-39 Yrs
1990-1994
40-44 Yrs
1999-2003
45 Yrs and Over
*Less than 37 weeks gestation
**Overall percent of babies born prematurely for Minnesota in 2003
Prenatal Care
Early and regular prenatal care can lead to improved birth outcomes. It is especially important for older women
because as data in this edition has shown, having children later in life increases the risk for poor birth outcomes.
The data indicate several trends for older women seeking prenatal care. In 2003, the overall percent of mothers in
Minnesota receiving late or no prenatal care was 2.1 percent. Among women 35-39 years old, the percent of
women receiving late or no prenatal care was lower than the overall rate. Just 1.6 percent of the 35-39 year olds
initiated prenatal care in the third trimester or not at all. Interestingly, the percent of women in the 40-44 year old
age group (2.7 percent) is higher than the overall percent. Also interesting is the high percent of women 45 years
and older (3.9 percent) receiving prenatal care in the third trimester or not at all.
Figure 6: Percent of Women Receiving Prenatal Care in the Third
Trimester of Not at All, Minnesota, Selected Years
25.0
19.1
Percent
20.0
16.4
15.0
7.3
10.0
5.0
3.9
2.2
4.3
3.9
1.6 2.7
2.1*
0.0
1980-1984
35-39 Yrs
1990-1994
40-44 Yrs
1999-2003
45 Yrs and Over
*Percent of overall births in 2003 in which prenatal care was initiated in the third
trimester or not at all
Multiple Births
See Minnesota Vital Signs (Volume 1, No. 3). This volume indicates that the rate of multiple pregnancy increases
with age.
August 2005
4
Labor and Delivery
The percent of births to mothers 35 years and older delivered via Cesarean section has increased from 22.4 percent
in 1990 to 30.5 percent in 2003 (Figure 7). While the trend is similar for all births, the percent of Cesarean births
for mothers 35 years and older remains higher.
Figure 7: Percent Cesarean Sections,
Minnesota 1970-2003
35
30
Percent
25
20
15
35+
10
All Births
5
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1980
1970
0
Infant Mortality
In 2003, the overall infant death rate (number deaths to infants under 1 year of age per 1,000 live births) in
Minnesota was 4.7 per 1,000 births, one of the lowest in the country. These figures reflect dramatic decreases in
infant deaths since the 1930s. For women 35-39 and 40-44 years old the infant mortality rate has also decreased as
shown in Figure 9.
Figure 9: Infant Mortality Rate* by Age of Mother
Minnesota, Selected Years
Rate
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
12.0
10.1
9.1
8.1
6.8
5.5
4.7**
1980-84
1990-1994
35-39 Yrs
1998-2002
40-44 Yrs
*Number of deaths to infants under 1 year of age per 1,000 live births
**Overall infant mortality rate for Minnesota in 2003
For women 35-39 and 40-44 years old, infant mortality rates show a steady decline from 1980-84 figures. While
the current rate for the 35-39 year old age group of 5.5 per 1,000 births is only slightly higher than the overall rate,
the rate for 40-44 year olds (8.1 per 1,000) is dramatically higher.
August 2005
5
Minnesota Vital Signs
Minnesota Center for Health Statistics
Office of Health Policy, Statistics and Informatics
Minnesota Department of Health
Vital Signs is available on the Minnesota Center for Health Statistics website,
http://www.health.state.mn.us/divs/chs/vitalsigns/index.html. If you require this document in
another format such as large print, Braille, or cassette tape call 651/296-1232 or email
[email protected].
Protecting, maintaining and improving the health of all Minnesotans