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4102.0 - Australian Social Trends, 2001  
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 06/06/2001   
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Contents >> Family >> Family Formation: Older mothers

Family Formation: Older mothers

In 1979, almost one in four births were to women aged 30 years and over. By 1999 this had increased to almost one in every two births.

Since the late 1970s, an increasing number of women are having children later in life. Older motherhood can largely be seen as a consequence of later timing of the events in people’s lives which generally lead to family formation. Young adults are tending to live in the parental home longer and are more likely to be undertaking post-school education (see Australian Social Trends 2000, Young adults living in the parental home). They are also more likely to enter into de facto relationships which may be short-term or precede marriage, thus marrying or entering into long-term relationships later.1 Other changes in society, particularly the increased level of participation by women in the labour force and the widespread use of effective contraceptive methods, have also contributed to delayed family formation and subsequent older motherhood.


Births and fertility
Births data are provided by Registrars in each State and Territory. The data are derived from Birth Registrations which are generally completed by at least one parent.2

A birth is the delivery of a child, irrespective of the duration of pregnancy, who, after being born, breathes or shows any evidence of life, such as a heartbeat.

An age-specific fertility rate is the number of live births, according to the age of the mother, per 1,000 of the female resident population at the same age at 30 June.

The total fertility rate is the sum of age-specific fertility rates (live births at each age of mother per 1,000 female population of that age). It represents the number of babies a woman would bear during her lifetime if she experienced current age-specific fertility rates at each age of her reproductive life.


Changing age profile of mothers
Since the peak in 1961, the total fertility rate of Australian women has been declining. Between 1969 and 1979, the total fertility rate dropped from 2.9 to 1.9 babies per woman. Much of this drop can be attributed to a rapid decline in the fertility rates of women in the 20-24 and 25-29 year age groups, although women of all age groups experienced some decline in fertility rates during this period.

AGE-SPECIFIC FERTILITY RATES(a)

(a) Births per 1,000 females.

Source: Births, Australia, 1999 (cat. no. 3301.0).


Between 1979 and 1999, the total fertility rate decreased slightly from 1.9 to 1.7 babies per woman. However, this period saw a noticeable change in the timing of births. The fertility rate of women aged under 30 years continued to decline while that of women aged 30-34 years increased by 47% (from 74 births per 1,000 women in 1979 to 109 per 1,000 in 1999). At the same time, the fertility rate of women aged 35-39 years doubled (from 24 to 47 births per 1,000 women), as did that for women in the 40-44 years age group (from 5 to 9 births per 1,000 women). Nevertheless, the gains made in the older age groups did not make up for the drop in fertility in the younger age groups.

The changes in the proportion of births occurring to women of different age groups further illustrates the shift towards older motherhood. In 1979 nearly one in four births (24%) were to women aged 30 years and over. In 1999, nearly one in two births (47%) were to women aged 30 years and over. The biggest change has occurred in the 15-24 years age group, with the proportion of births declining from 46% of all births in 1969 to 20% in 1999. The proportion of births to women aged 25-29 years remained relatively steady.

PROPORTION OF ALL BIRTHS BY AGE OF MOTHER

Source: Births, Australia, 1969, 1979, 1989 and 1999 (cat. no. 3301.0).


Timing of first children
The falling fertility rates of women aged under 30 years and the rising fertility rates of women in their thirties and early forties, are consistent with women having their first and subsequent births later in life.

Although the proportion of first births to all births remained relatively steady between 1993 and 1999, there was a change in the age distribution of mothers having their first birth. Women experiencing their first birth in 1999 tended to be older than women having a first birth in 1993. Approximately 28% of all first births in 1993 were to women aged 30 years and over. By 1999 this had increased to 34%. In contrast, 31% of all first births in 1999 were to women aged 15-24 years (down from 37% in 1993).

Census data on the number of children ever born to a woman provide further evidence that women are tending to have their first child later in life. In 1986, 67% of women aged 20-24 years had not had a child. By 1996 this had increased to 76%. In 1986, 40% of women aged 25-29 years had not had a child. This increased to 53% in 1996.2 Not all of these women will give birth later in life as some will remain childless (26% based on 1999 rates).2

The later a woman has her first child, the later she will have other children. Between 1993 and 1999, the proportion of second births to women aged 30 years and over increased from 44% to 52%.

FIRST AND SECOND BIRTHS

1993
1999

%
%
Age of mother at first birth
    15-24 years
37.3
31.0
    25-29 years
35.2
35.0
    30-34 years
20.8
24.1
    35 years and over
6.8
9.9
    Total
100.0
100.0

Total mothers (no.)
112,906
104,735
First births as a proportion of all births (%)
43.4
42.1
Second births to women aged 30 years and over(a) (%)
44.2
51.6

(a) As a proportion of all second births.

Source: ABS 1993 and 1999 Births Collection.


Later family formation and older motherhood
Between 1979 and 1999, the median age of all women giving birth increased by three years.2 The shift towards having children later in life results from young people tending to reach the milestones which usually precede parenthood (leaving the parental home, gaining economic independence, and marrying or forming long-term de facto relationships) later than was the case in previous decades.

Those who decide to become partners and parents are more likely to do so after establishing themselves in a job or career.3 A lack of economic independence may therefore constrain family formation. A number of indicators suggest that it is taking young people longer to gain economic independence. These indicators include: a higher proportion of young adults under the age of 25 years in post-school education, a higher proportion of people in this age group living in the parental home and the increased rates of part-time employment and underemployment for persons in this age group (see Australian Social Trends 1999, Decline of the standard working week).

Social and economic changes occurring in the latter half of the 20th century triggered a shift in attitudes towards family formation, reproduction and women’s participation in the labour force. As a result, women have taken on alternative roles and life styles to motherhood.4 Labour force participation rates for women have increased noticeably since the 1970s and much of the increase can be attributed to greater numbers of married women entering the labour force. The labour force participation rates of married women in the 20-34 year age group (the major child-bearing ages during the last two decades) increased from 48% in 1979 to 65% in 1999. Increased access to the oral contraceptive pill from the 1960s (see Australian Social Trends 1998, Family planning) also enabled women to delay parenthood while participating in the labour force.

The changing nature and permanency of partnerships may also be factors in the timing of parenthood. It is becoming more likely for a person to live with more than one partner over a lifetime, in either a registered marriage or a de facto relationship, some of which are of a temporary nature.1

Of marriages registered in 1999, 69% were preceded by a period of cohabitation. If couples form de facto relationships to trial their compatibility or suitability for marriage, they may delay parenthood until they are confident in the permanency of a relationship. Increasing divorce rates (almost one in two marriages will end in divorce based on 1999 rates)5 may also contribute to later parenthood if women repartner and begin a second family at older ages.

SELECTED INDICATORS RELATING TO LATER FAMILY FORMATION

1979
1999

Living in the parental home
    Males aged 20-24 years (%)
(a)51.3
53.7
    Males aged 25-29 years (%)
(a)17.2
22.1
    Females aged 20-24 years (%)
(a)31.6
40.5
    Females aged 25-29 years (%)
(a)6.8
11.5
Education participation rates
    Males aged 15-19 years (%)
(b)59.5
77.9
    Males aged 20-24 years (%)
(b)20.0
33.9
    Females aged 15-19 years (%)
(b)51.6
77.8
    Females aged 20-24 years (%)
(b)13.0
34.8
Female’s participation in the labour force
    Females aged 20-34 years (%)
57.1
71.7
    Married females aged 20-34 years (%)
48.3
65.4
Co-habitation
    Registered marriages preceded by cohabitation (%)
23.0
68.9
Median age at first marriage
    Males (years)
24.1
28.2
    Females (years)
21.7
26.4
Median age of females giving birth
    Nuptial (years)
26.9
30.6
    Exnuptial (years)
21.6
25.9
    All births (years)
26.5
29.7
Median age at remarriage
    Divorced males remarrying (years)
36.1
42.2
    Divorced females remarrying (years)
32.6
38.6

(a) June 1986 data.
(b) May 1982 data.

Source: ABS 1979, 1986 and 1999, Labour Force Survey (data have not been revised to reflect definitional changes introduced in April 2001); Transition from Education to Work, Australia, 1982 (cat. no. 6227.0); ABS Transition from Education to Work Survey; Marriages and Divorces, Australia (ABS cat. no. 3310.0); Marriages, Australia, 1979 (cat. no. 3306.0); Births, Australia, 1979 and 1999 (cat. no. 3301.0).


Health and reproduction issues associated with older motherhood
There are health risks which escalate when a woman has children later in life, particularly if she is aged 35 years or over. These risks can include potentially life-threatening conditions for the mother and/or the baby, and the increased chance of giving birth to a child with a chromosomal disorder. Also, although quite low, the perinatal death rate is higher for babies born to women who are 40 years and over than it is for women in the 20-39 years age group. Between 1992 and 1997 the perinatal death rate for babies born to women aged 40 years and over varied between 12 and 18 deaths per 1,000 births. The perinatal death rate for babies born to women aged 20-39 years varied between 9 and 10 deaths per 1,000 births.

PERINATAL(a) DEATH RATES(b) BY AGE OF MOTHER

(a) A perinatal death is stillbirth or a death recorded within 28 days of birth.
(b) Deaths per 1,000 births.

Source: Day, P., Sullivan, E.A., Ford, J. and Lancaster, P. 1999, Australia’s Mothers and Babies 1997, AIHW National Perinatal Statistics Unit: Perinatal Statistics Series no. 9, Sydney.


The ability to conceive declines markedly from age 35 years onwards.6 The proportion of assisted conception pregnancies to women aged 35 years and over in Australia and New Zealand increased from 29% of all assisted conception pregnancies in 1990 to 41% in 1997. During this time the number of assisted conception pregnancies doubled. Given that women aged 35 years and over have a lower overall ability to conceive, the increase is a reflection of the trend towards older motherhood. One of the issues facing women considering assisted conception is the increased likelihood of multiple births. Multiple pregnancies occurred in 20% of IVF (in-vitro fertilisation) pregnancies in 1997. The rate was slightly lower that year for GIFT (gamete intrafallopian transfer) pregnancies.7 This is much higher than the overall proportion of multiple births (1.4%) that occurred in Australia in 1997.2

IVF(a) AND GIFT(b) PREGNANCIES(c) BY AGE OF MOTHER, AUSTRALIA AND NEW ZEALAND

1990
1997


no.
%
no.
%

15-24 years
42
2.1
75
1.9
25-29 years
521
26.1
688
17.2
30-34 years
854
42.8
1,588
39.8
35-39 years
485
24.3
1,294
32.4
40 years and over
93
4.7
346
8.7
Total
1,995
100
3,991
100.0

(a) In-vitro fertilisation.
(b) Gamete intrafallopian transfer.
(c) Includes ectopic pregnancy, blighted ovum and spontaneous abortion.

Source: AIHW National Perinatal Statistics Unit, Assisted conception, Australia and New Zealand, 1990 and 1997.


Endnotes
1 Australian Parliament 1998, To have and to hold, a report of the inquiry into aspects of family services, House of Representatives Standing Committee on Legal and Constitutional Affairs, Can Print Communications, Pty Ltd, Parliamentary Paper 95, Canberra.

2 Australian Bureau of Statistics 2000, Births, Australia, 1999, cat. no. 3301.0, ABS, Canberra.

3 Australian Bureau of Statistics 1994, Focus on Families: Work and Family Responsibilities, cat. no. 4422.0, ABS, Canberra.

4 Jain, S. and McDonald, P, ‘Fertility of Australian Birth Cohorts: Components and Differentials’, Journal of the Australian Population Association, vol 14, no. 1, 1997, pp. 31-46.

5 Australian Bureau of Statistics 2000, Marriages and Divorces, Australia, 1999, cat. no. 3310.0, ABS, Canberra.

6 Bourne, G, and Gillard, M.1995, Pregnancy, Pan Books, London.

7 Hurst, T., Shafir, E. and Lancaster, P. 1999, Assisted Conception Australia and New Zealand 1997, AIHW National Perinatal Statistics Unit, Sydney.



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