Over the past few decades, women in Switzerland — and across much of the developed world — have been having children increasingly later in life. This insight examines the age of mothers at birth in Basel-Stadt, tracing how it has shifted over time and how Basel-Stadt compares with other Swiss cantons and the national average. A key indicator used here is the Total Fertility Rate (TFR) — the average number of children a woman would have over her reproductive lifetime (conventionally defined as ages 15 to 49), assuming that the birth rate observed in a given year remains constant. A TFR of 2.1 is considered the replacement level at which a population maintains its size without migration. More details on the methodology can be found on Wikipedia.

In 2025, there were 1'835 births in Basel-Stadt, of which 1'038 were to Swiss mothers and 638 to foreign mothers, with 159 births where the mother's nationality was unknown (Table 1). This represents an increase from the 1'779 births recorded in 2024, when 985 were to Swiss mothers and 611 to foreign mothers.

The long-term trend in Basel-Stadt shows a clear shift toward older motherhood. In 2005, the largest group of mothers was aged 30 to 34, with 505 births, while 317 mothers were under 25 and only 74 were over 39. By 2025, the largest group had become mothers aged 35 to 39, with 661 births, followed closely by those aged 30 to 34 with 664 births, while the number of mothers under 25 had fallen sharply to just 76, and those over 39 had more than doubled to 166 (Figure 1). This trend is even more pronounced among Swiss mothers compared to foreign mothers, though both groups show the same direction. At the youngest end of the age spectrum, births to mothers under 20 have dropped from 33 in 2005 to just 5 in 2025, while at the oldest end, births to mothers over 39 have risen from 74 to 166 (Figure 4).

Across Switzerland, the same pattern of delayed childbearing is evident. In 1970, the most common age group for mothers in both Switzerland and Basel-Stadt was 25 to 29, accounting for 35.8% and 36.8% of births respectively (Figure 4). By 2024, the most common age group in Switzerland had become 30 to 34, at 39.6%, while in Basel-Stadt it had shifted even further to 35 to 39, at 36.9%. The lines representing the share of younger mothers (under 25) and older mothers (over 35) crossed in Basel-Stadt earlier than in Switzerland as a whole, reflecting the city's more pronounced trend toward later motherhood.

The total fertility rate in Basel-Stadt stood at 1.09 in 2024, below the Swiss average of 1.29 and the rate in Zürich of 1.23 (Figure 5). The highest fertility rate recorded in Switzerland since 1982 was in Appenzell Innerrhoden in 1983, at 2.97, a level far above replacement. In contrast, Appenzell Innerrhoden's fertility rate had fallen to 1.36 by 2024, still higher than Basel-Stadt's but reflecting the broader national decline.

In summary, Basel-Stadt exemplifies the Swiss trend of increasingly older motherhood, with the most common age for giving birth now in the late thirties rather than the late twenties. The most striking finding is that in Basel-Stadt, mothers aged 35 to 39 have become the largest group, surpassing even the 30 to 34 age group, a shift that has not yet occurred at the national level. At the same time, the city's fertility rate remains well below the replacement level and below the national average, highlighting the demographic challenges of an urban population with delayed childbearing.