Women aged 20 and under are having fewer babies than women over 40 for the first time in nearly 70 years, according to new data. The last time over-40s had more babies was in 1947 – just after WWII. Fertility rates declined among women in all age groups under 25 in 2015, and increased among women aged 30 and over, according to a report for the Office for National Statistics (ONS). Teenage motherhood has been declining since 1999, and in 2015 the largest percentage decrease in fertility rates was for women aged under 20 (7.1%). The teenage pregnancy rate has more than halved since 1990, the BBC reported. By contrast, the largest percentage increase was among women aged 40 and over (3.4%). The fertility rate of women aged 40 and over has more than trebled since 1981, the ONS reported. While it’s common knowledge that women are waiting until later in their lives to have babies, these figures highlight just how much women’s role in society has changed over the last few decades. The ONS report attributed the trend to factors including “increased female participation in higher education and the labour force, the increasing importance of a career, the rising costs of childbearing, labour market uncertainty and housing factors”. Advances in fertility treatment, such as IVF, have also contributed to the change. The increase in fertility rates among older women has affected the average age of mothers, which has been increasing since 1975. In 2015, the average age was 30.3 years, the ONS said. Fertility was highest among women aged 30 to 34, which hasn’t changed since 2004. Before this, women aged 25 to 29 had the highest fertility. While many continue to define a woman by whether or not she has children, this data is a stark reminder that the way many of us think about motherhood is changing: it's now just one of many options in our lives. It’s time for the dinosaurs to catch up.