7. Most common age at childbirth continues to increase

Fertility rates (live births per thousand women of childbearing age) continue to rise mainly for women over 30 years but are declining for those younger than 30 years. Childbearing in teenage years remains low, as just 6% of 20-year-old women from the 1997 cohort had given birth by age 20 years. There has been a gradual decline since the 1991 cohort in which 10% of women had given birth by age 20 years. In the 1945 cohort, 17% had had at least one child by age 20 years, almost treble the percentage of the 1997 cohort.

Figure 4 shows the changing pattern of fertility that we have seen in England and Wales over the last 70 years, from selected cohorts born between 1925 and 1995.

Figure 4: Live births per thousand women for ages 15 to 45 years, selected cohorts born between 1925 and 1995 England and Wales Source: Birth registrations, Office for National Statistics Notes: These data are presented by age in completed years. Download this chart Figure 4: Live births per thousand women for ages 15 to 45 years, selected cohorts born between 1925 and 1995 Image .csv .xls

This chart shows the age at which births were most prevalent for each of the selected cohorts. Data for the 1925, 1935 and 1945 cohorts show the highest number of births per thousand women were occurring when women were in their early to mid-twenties. By the 1955 and 1965 cohorts, the peak age at which women were having children was in their mid-to-late 20s and by the 1975 and 1985 cohort, who have yet to complete their childbearing years, the highest number of live births per thousand women occurred when women were in their early 30s. This is evidence that women are tending to delay their childbearing.

The fertility of the latest cohort likely to have completed their childbearing, born in 1972, peaked at the age of 31 years.

It is clear also, that for the later cohorts, the data points have “flattened” out, suggesting that women are tending to spread births more over their childbearing lifetime than previous cohorts. There is evidence (as depicted in Figure 4) that women are generally having fewer children at a given age; for instance, at its highest point, the 1935 cohort had close to 200 births per thousand women in a single year but by the 1985 cohort, the highest number was just under 120 births per thousand.

The 1975 cohort shows a clearly higher fertility rate for women in their mid- to late-30s than for previous cohorts. The most recent cohort visible on the chart (born in 1995) is so far displaying a “flatter” trend, showing the recent decrease in births to teenage mothers. It is probable that the 1995 cohort will continue in the same way as the 1975 and 1985 cohorts, in that there will be a lower fertility rate in their 20s compared to previous cohorts, but higher fertility rates at older ages.

Changes in the fertility rate (number of births per thousand women) for women aged between 20 and 45 years are shown in Figure 5.

Figure 5: Age-specific fertility rates at selected ages, by year of birth of woman, 1920 to 1997 England and Wales Source: Birth registrations, Office for National Statistics Notes: These data are presented by age in completed years. The 1945 cohort is assumed to be their mothers' generation because the average age of mothers giving birth in 1972 was 27 years, and so women of that age were assumed to be born in 1945. Download this chart Figure 5: Age-specific fertility rates at selected ages, by year of birth of woman, 1920 to 1997 Image .csv .xls

In general, fertility rates for women aged 20 and 25 years have fallen but rates for over-30s have risen; this trend is most evident for the latest cohorts. Proportions for the latest cohorts to reach ages 20 and 25 years are the lowest rates recorded to date. Women aged 25 in 2017 had a rate of just 77 births per thousand, while for women born in 1997, who turned 20 in 2017, the rate at age 20 years had fallen below 40 births per thousand.

At age 30 years, considered to be the mid-point of the childbearing years, births per thousand women have steadied at around 115 births per thousand women. Fertility rates at age 40 and 45 years are at the highest levels recorded to date for the latest cohorts to reach those ages. Women aged 40 years in 2016 and 2017 had a rate of 30 births per thousand women, while women aged 45 years in 2017 had a rate of six births per thousand.

The latest data reflects a tendency for women to postpone childbearing. Some of the reasons may include:

participating in higher education

Delaying marriage and/or partnership formation

wanting to start a career, get on the housing ladder and ensure financial stability before starting a family1

Notes for: Most common age at childbirth continues to increase