The rise of the older mother.

Author:Kippen, Rebecca

In Australia, declining fertility among younger women is partly off-set by increasing fertility among women over 30. Women born in 1971 are projected to have an average of 1.9 children each, with almost half their children born after the age of 30. Levels of childlessness for these women will be much less than previously estimated. Future levels of fertility will depend on whether birth rates at older ages continue to rise. From a demographic perspective there is potential for further increase, since probably half of women are still fecund at age 40. From an individual perspective, women should have children before age 35 if circumstances are conducive.


For the first time in Australia's recorded history, women are now more likely to give birth in their thirties or forties than in their teens or twenties. (1) Over the past 30 years, birth rates under the age of 30 have dropped 50 per cent, while rates over age 30 have risen by more than half. The mean age of mothers at birth has steadily increased over the same period, from 26.7 years in 1974 to 30.0 years in 2004. (2) Almost half of all 30-year-old women in 2004 had not had children, (3) up from 20 per cent in 1981. (4) However most of these women still expect to have children at some time in the future. (5)

One fundamental question is whether fertility at younger ages will continue to decline and, if so, whether these declines will be offset in the future by increasing birth rates at older ages. This leads to another question about women's capacity to continue delaying childbearing given that the vast majority of women hit a reproductive impasse in their late thirties or forties.

This paper briefly discusses the causes and possible consequences of delayed motherhood. It then examines long-term trends in Australian fertility by age and long-term patterns of parity distribution, the implications of these for future fertility, and the potential for future increase in fertility rates at older ages.


The trend to delayed parenting has been attributed to several factors. Research in Australia and elsewhere shows a strong correlation between education and deferred parenthood. For example, Australian women born between 1945 and 1964 delayed their first birth by 0.75 years for every extra year of education between the ages of 15 and 24 years. (6) Thus, increasing levels of education herald further delays in childbearing. Rising levels of female labour force participation are also associated with postponed parenthood. (7) McDonald argues that the trend to delayed parenting is because--in an increasingly competitive labour market--young people need to build up human capital based on education and work experience before taking on the parental role. (8)

Related to this, young Australians are leaving home, gaining financial independence and forming stable relationships progressively later in life, delays which inhibit the commencement of family formation. (9) Overarching all these factors are scientific advances. These have resulted in greater reproductive autonomy, allowing potential parents to delay childbearing or to avoid parenthood altogether.

Although the trend to deferred motherhood is tied to rising levels of education, labour force participation and reproductive autonomy, all of which are laudable changes, the trend itself is of concern for several related reasons.

First, some women who defer motherhood run out of time and end their reproductive years childless, or with fewer children than they had intended to have. Cannold documents the heartache of 'thwarted mothers': women whose desire to have children has not been realised. (10)

Second, all else being equal, older mothers (35 years and over) are at greater risk of health problems during pregnancy. Age is also associated with an increased likelihood of chromosomal abnormalities, premature birth, miscarriage and perinatal mortality. On the positive side, older mothers and their babies today enjoy significantly better outcomes than their counterparts of 20 years ago (11) and, overall, the risks are small. (12)

The third reason concerns Australia's birthrate, as mentioned above. Studies show that age at first birth is strongly negatively correlated with completed fertility. (13) That is, on average, the later you start, the fewer you have. In Australia, women's average age at first birth increased from 25.6 years in 1981 to 28.3 years in 2000. (14) Progressively later entry into parenthood implies a continuing decline of Australian fertility, a possibility which attracts widespread public concern. (15) Substantial falls in fertility could lead to hyper-ageing of the population, contraction of labour supply and spiralling population decline. (16)



The most commonly cited measure of fertility internationally is the Total Fertility Rate (TFR). For any one year, the TFR gives the average number of births a woman would have over her lifetime if she were to experience the age-specific fertility rates of that particular year. Age-specific fertility rates are calculated as the annual number of births to women of a particular age divided by the mid-year female population of that age. The TFR is thus a hypothetical measure of the average number of children born over a woman's lifetime, since it refers to cross-sectional (or period) data on births rather than to births of a real cohort of women. Its advantage is that it requires only one year of data and gives a very current view of fertility.

Australia's TFR over the years 1921 to 2005 is shown in Figure 1, disaggregated by age group. (17) The interpretation of these rates is straightforward. For example, a hypothetical group of women experiencing the age-specific fertility rates of 2004, would have had, on average, 0.1 of a child each in their teens, 0.3 at age 20-24, 0.5 at age 25-29, 0.6 at age 30-34, 0.3 at age 35-39, and 0.1 in their forties, making for a total of 1.8 births each over their (hypothetical) lifetimes.

In the 1920s, fertility rates at all ages were higher than they are today. What is particularly striking is the level of fertility over the age of 35 years, which is more than twice that of 2004 (the most recent year for which age-specific data are available). The 1930s depression saw a contraction of fertility at all ages. In the 1940s and 1950s fertility increased at all ages under 40, and particularly under age 30. The collapse of fertility through the 1960s and early 1970s was associated with declining fertility at every age bar the teenage years.


Over the period 1984-2005, Australia's TFR sat between 1.7 and 1.9 births per woman. This is the lowest it has been since national-level data collection began in 1921. Although aggregate fertility has varied little over the past two decades, fertility at different ages has changed greatly. Since 1984, fertility under the age of 30 years has fallen by more than one-third. This decline has been partly compensated for by increases at older ages, such that women in their thirties now have more children than do women in their twenties.

A question raised in the introduction to this paper is whether fertility at younger ages will continue to decline and, if so, whether these declines will...

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