Teenage pregnancy and fertility in New South Wales: an examination of fertility trends, abortion and birth outcomes Pamela L. Adelson, Michael S. Frommer, Margaret A. Pym and George L. Rubin Epidemiology and Health Services Evaluation Branch, New South Wales Health Department Abstract:This paper reviews the data available in New South Wales on teenage fertility rates and pregnancy outcomes. Teenage births comprise six per cent of all births in New South Wales, but they constitute a significant public health problem because they are associated with elevated rates of adverse pregnancy outcomes, which include low birthweight, perinatal death and pre-eclampsia. Risk is concentrated in females under 18 years of age. Pregnancy outcomes for females aged 18 to 19 years are similar to those of women aged 20 to 24 years. Teenage fertility rates have remained stable since the mid-l980s, following a decline which began in the early 1970s. There are large geographic variations in teenage fertility within the state, with the highest rates in the far west of New South Wales and in western Sydney. Teenage p r e p n q in New South Wales (as distinct from fertility which reflects births) cannot be assessed accurately because of the lack of information on terminations of pregnancy. However, available data suggest that teenage pregnancy rates have not increased d;riGg the’1980s. (AustJ Public Health 1992; 16: 238-44)
P
ublic health strategies aimed at improving pregnancy outcomes depend upon identifying and characterising population subgroups having adverse outcomes. In Australia, teenage females comprise such a subgroup; reports from Australia and overseas have shown that, compared with women aged 20 years or more, infants born to teenagers are at greater risk of having low birthweight and have higher perinatal mortality. 1t4.y.4 The pregnant teenager frequently faces unfavourable social and economic circumstances, and available evidence suggests that socioeconomic forces may outweigh the influence of biological factors in teenagers’ adverse pregnancy outcomes.Y Epidemiological data on teenage pregnancy in New South Wales is patchy. Teenage fertility rates, as recorded by the Australian Bureau of Statistics (ABS),have declined markedly from 58 live births per 1000 teenage females in 1971 to 21 per 1000 in 1989. Most of this decline occurred during the 1970s, and has been attributed to improved contraceptive practice, a decline in nuptial births, and an increase in terminations of pregnan~y.~ Information on teenage pegnumy (as distinct from fertility, which reflects births) is scanty, the major gap being statistics about induced and spontaneous abortions. This paper synthesises the available information on teenage pregnancy in New South Wales in the context of information from elsewhere in Australia. Specifically, it examines trends in teenage fertility: antenatal and obstetric factors associated with teenage pregnancy, and key determinants of Correspondence to Ms Pamela L Adelson, Epidemiology and Health Services Evaluation Branch, NSW Health Department, Locked Bag 961, North Sydney 2060
238
perinatal outcomes of teenage pregnancy. The paper also discusses the available data on termination of pregnancy in teenagers.
Methods Because definitions and the ascertainment of rates relevant to teenage pregnancy are not standardised, equivalent rates published elsewhere may differ slightly from those given in this paper. The following represent conventional expressions: A teenager is a female aged 13 to 19 years. The teenage fertility rate is the number of live births registered during a calendar year to mothers aged 13 to 19 years at the time of confinement, per 1000 of the estimated female resident population aged 15 to 19 years on 30 June of the same year. Females aged 13 to 14 years are included in the numerator but not the denominator. They account for only 0.5 per cent of all teenage births. An abortion is taken to mean an induced termination of pregnancy. The abortion rate is the number of abortions per 1000 females in a specified age group. For consistency with the teenage fertility rate, the teenage abortion rate is defined as the number of abortions to females aged 13 to 19 years in a calendar year, per 1000 of the estimated female resident population aged 15 to 19 years on 30 June of the same year. The abortion ratio is the number of abortions divided by the sum of the number of abortions and the number of live births in the same time period. Strictly speaking it is a proportion rather than a ratio. The teenage abortion ratio applies specifically to females aged 13 to 19 years.
AUSTRALIAN JOURNAL OF PUBLIC HEALTH
1992
VOL.16 NO.
3
TEENAGE PREGNANCY
The 1987 New South Wales Maternal and Perinatal Collection (NSWMPC) (later renamed the Midwives' Data Collection), was used to examine teenage births for the year 1987.6Whenever a birth occurred in New South Wales, the attending midwife filled in a data-collection form which included demo-. graphic items and items on maternal health, the pregnancy, labour, delivery, and perinatal outcomes. Completed forms were sent to the Epidemiology Branch, NSW Health Department, where they were compiled into a database. In 1987, a total of 4 690 births to 4 655 teenage mothers were reported to the NSWMPC, which was 98 per cent complete for this age range.6 The NSWMPC was known to be incomplete for perinatal deaths as the NSWMPC form was filled in by the attending midwife at birth. Therefore the perinatal mortality rates published by the ABS were higher than those obtained from the NSWMPC. The NSWMPC was notified of 62 perinatal deaths following teenage pregnancies, while 71 were known to have been registered and recorded in ABS statistics. Australian Bureau of Statistics (ABS) published reports were used to examine trends in fertility rates, and provided denominator data for New South Wales and other States and territorie~.~.~?." Relative risks and confidence intervals were used when reporting associations of risk factors with poor perinatal outcomes.
1980
'81
'82
-NT
- - Tas
Figure
'84 '85 Ye=
83
-.I.- a
--- WA
'86
llll~l~lsl
NSW SA
'87
'88
'89
-wc
.....
ACT
1 : Teenage fertility rotes, Australian states and territories,
1 980-1 989.
Results Teenage fertility rates There was a dramatic decline in teenage fertility rates across Australia during the 1970s which continued (although at a slower pace) during the 1980s. The teenage fertility rate for Australia as a whole was 57.8 per 1000 teenage females in 1971,27.6 in 1980 and 20.6 in 1989. While all states and territories have shown a downward trend, large differences in teenage fertility rates among the states and territories have persisted throughout the 1980s (Figure 1). Teenage fertility rates for the year 1989 are shown in Table 1. The New South Wales teenage fertility rate during the 1980s declined from 28.7 per 1000 in 1980 (based on 6 276 live births) to 21 .O per 1000 in 1989 (based on 4 824 live births). Teenage births as a pro-
portion of all New South Wales births remained stable at about 5.5 per cent over the years 1985 to 1989. Births to young teenagers (aged under 18 years) during the later 1980s also remained stable, representing 28 to 31 per cent of all teenage births. An examination of teenage fertility characteristics using the 1987 NSWMPC showed that the majority of teenage confinements (83 per cent) were of females giving birth for the first time, and 70 per cent of teenage confinements were of females aged 18 to 19 years (Table 2). However, confinements of Aboriginal teenagers had a different pattern, with Aboriginal Australians being overrepresented in the number of teenage confinements, as well as being younger (Table 3). New South Wales Aboriginal teenagers had a fertility rate of 83.0 compared with a fertility rate of 19.6 for non-Aboriginal teenagers. Of the 1283 births to New South Wales Aboriginal Australians of all ages in 1987, 26 per cent were to teenagers; only 5 per cent of non-Aboriginal births were to teenagers. Teenage fertility rates also showed great variation among the 16 Area Health Services in New South Wales, with rural regions and Western Sydney having the highest rates (Table 4).
Table 1 : Teenage fertility rates (live births per 1000 females aged I5 to 19) in Australia, 1989
Table 2: Teenage maternal age by parity, New South Wales, 1987
State or Territory
Fertility Rate
Victoria
77.6 26.8 24.1 22.2 21.2 21 .o 14.9
Australian Capital Territory
10.8
Northern Territory Tasmania Queensland Western Australia South Australia New South Wales
Maternol age
13 14 15 16
17 18 19 Total
Note: Source - ABS
AUSTRALIAN JOURNAL
OF
PUBLIC HEALTH
1992
Primiparae Multiparae
Total
n
n
n
5 19 97 400 762 1 I72 1402 3857
0 0 0 16 79 23 1 472 798
5 19 97 416 841 1403 1874 4655
VOL. 16 NO.
3
%
0.1 0.4 2.1 8.9 18.1 30.1 40.3 100.0
239
ADELSON ET AL.
Table 3: Teenage confinements by maternal age and Aboriginality, New South Wales, 1987 Age in years
< I5
Aboriginal
Nan-Aboriginal
%
n
15 16 17 18 19
3 18 45 63 97 102
Totol
328
1
Total teenagers
%
n
n
%
P
ublic health strategies aimed at improving pregnancy outcomes depend upon identifying and characterising population subgroups having adverse outcomes. In Australia, teenage females comprise such a subgroup; reports from Australia and overseas have shown that, compared with women aged 20 years or more, infants born to teenagers are at greater risk of having low birthweight and have higher perinatal mortality. 1t4.y.4 The pregnant teenager frequently faces unfavourable social and economic circumstances, and available evidence suggests that socioeconomic forces may outweigh the influence of biological factors in teenagers’ adverse pregnancy outcomes.Y Epidemiological data on teenage pregnancy in New South Wales is patchy. Teenage fertility rates, as recorded by the Australian Bureau of Statistics (ABS),have declined markedly from 58 live births per 1000 teenage females in 1971 to 21 per 1000 in 1989. Most of this decline occurred during the 1970s, and has been attributed to improved contraceptive practice, a decline in nuptial births, and an increase in terminations of pregnan~y.~ Information on teenage pegnumy (as distinct from fertility, which reflects births) is scanty, the major gap being statistics about induced and spontaneous abortions. This paper synthesises the available information on teenage pregnancy in New South Wales in the context of information from elsewhere in Australia. Specifically, it examines trends in teenage fertility: antenatal and obstetric factors associated with teenage pregnancy, and key determinants of Correspondence to Ms Pamela L Adelson, Epidemiology and Health Services Evaluation Branch, NSW Health Department, Locked Bag 961, North Sydney 2060
238
perinatal outcomes of teenage pregnancy. The paper also discusses the available data on termination of pregnancy in teenagers.
Methods Because definitions and the ascertainment of rates relevant to teenage pregnancy are not standardised, equivalent rates published elsewhere may differ slightly from those given in this paper. The following represent conventional expressions: A teenager is a female aged 13 to 19 years. The teenage fertility rate is the number of live births registered during a calendar year to mothers aged 13 to 19 years at the time of confinement, per 1000 of the estimated female resident population aged 15 to 19 years on 30 June of the same year. Females aged 13 to 14 years are included in the numerator but not the denominator. They account for only 0.5 per cent of all teenage births. An abortion is taken to mean an induced termination of pregnancy. The abortion rate is the number of abortions per 1000 females in a specified age group. For consistency with the teenage fertility rate, the teenage abortion rate is defined as the number of abortions to females aged 13 to 19 years in a calendar year, per 1000 of the estimated female resident population aged 15 to 19 years on 30 June of the same year. The abortion ratio is the number of abortions divided by the sum of the number of abortions and the number of live births in the same time period. Strictly speaking it is a proportion rather than a ratio. The teenage abortion ratio applies specifically to females aged 13 to 19 years.
AUSTRALIAN JOURNAL OF PUBLIC HEALTH
1992
VOL.16 NO.
3
TEENAGE PREGNANCY
The 1987 New South Wales Maternal and Perinatal Collection (NSWMPC) (later renamed the Midwives' Data Collection), was used to examine teenage births for the year 1987.6Whenever a birth occurred in New South Wales, the attending midwife filled in a data-collection form which included demo-. graphic items and items on maternal health, the pregnancy, labour, delivery, and perinatal outcomes. Completed forms were sent to the Epidemiology Branch, NSW Health Department, where they were compiled into a database. In 1987, a total of 4 690 births to 4 655 teenage mothers were reported to the NSWMPC, which was 98 per cent complete for this age range.6 The NSWMPC was known to be incomplete for perinatal deaths as the NSWMPC form was filled in by the attending midwife at birth. Therefore the perinatal mortality rates published by the ABS were higher than those obtained from the NSWMPC. The NSWMPC was notified of 62 perinatal deaths following teenage pregnancies, while 71 were known to have been registered and recorded in ABS statistics. Australian Bureau of Statistics (ABS) published reports were used to examine trends in fertility rates, and provided denominator data for New South Wales and other States and territorie~.~.~?." Relative risks and confidence intervals were used when reporting associations of risk factors with poor perinatal outcomes.
1980
'81
'82
-NT
- - Tas
Figure
'84 '85 Ye=
83
-.I.- a
--- WA
'86
llll~l~lsl
NSW SA
'87
'88
'89
-wc
.....
ACT
1 : Teenage fertility rotes, Australian states and territories,
1 980-1 989.
Results Teenage fertility rates There was a dramatic decline in teenage fertility rates across Australia during the 1970s which continued (although at a slower pace) during the 1980s. The teenage fertility rate for Australia as a whole was 57.8 per 1000 teenage females in 1971,27.6 in 1980 and 20.6 in 1989. While all states and territories have shown a downward trend, large differences in teenage fertility rates among the states and territories have persisted throughout the 1980s (Figure 1). Teenage fertility rates for the year 1989 are shown in Table 1. The New South Wales teenage fertility rate during the 1980s declined from 28.7 per 1000 in 1980 (based on 6 276 live births) to 21 .O per 1000 in 1989 (based on 4 824 live births). Teenage births as a pro-
portion of all New South Wales births remained stable at about 5.5 per cent over the years 1985 to 1989. Births to young teenagers (aged under 18 years) during the later 1980s also remained stable, representing 28 to 31 per cent of all teenage births. An examination of teenage fertility characteristics using the 1987 NSWMPC showed that the majority of teenage confinements (83 per cent) were of females giving birth for the first time, and 70 per cent of teenage confinements were of females aged 18 to 19 years (Table 2). However, confinements of Aboriginal teenagers had a different pattern, with Aboriginal Australians being overrepresented in the number of teenage confinements, as well as being younger (Table 3). New South Wales Aboriginal teenagers had a fertility rate of 83.0 compared with a fertility rate of 19.6 for non-Aboriginal teenagers. Of the 1283 births to New South Wales Aboriginal Australians of all ages in 1987, 26 per cent were to teenagers; only 5 per cent of non-Aboriginal births were to teenagers. Teenage fertility rates also showed great variation among the 16 Area Health Services in New South Wales, with rural regions and Western Sydney having the highest rates (Table 4).
Table 1 : Teenage fertility rates (live births per 1000 females aged I5 to 19) in Australia, 1989
Table 2: Teenage maternal age by parity, New South Wales, 1987
State or Territory
Fertility Rate
Victoria
77.6 26.8 24.1 22.2 21.2 21 .o 14.9
Australian Capital Territory
10.8
Northern Territory Tasmania Queensland Western Australia South Australia New South Wales
Maternol age
13 14 15 16
17 18 19 Total
Note: Source - ABS
AUSTRALIAN JOURNAL
OF
PUBLIC HEALTH
1992
Primiparae Multiparae
Total
n
n
n
5 19 97 400 762 1 I72 1402 3857
0 0 0 16 79 23 1 472 798
5 19 97 416 841 1403 1874 4655
VOL. 16 NO.
3
%
0.1 0.4 2.1 8.9 18.1 30.1 40.3 100.0
239
ADELSON ET AL.
Table 3: Teenage confinements by maternal age and Aboriginality, New South Wales, 1987 Age in years
< I5
Aboriginal
Nan-Aboriginal
%
n
15 16 17 18 19
3 18 45 63 97 102
Totol
328
1
Total teenagers
%
n
n
%
