What it means: average ages adjusted so that changes in the number of women of each age do not distort the trend. Mothers were youngest in the mid-1970s; since then, more time in education, the cost of housing and later marriage have pushed parenthood later. Fathers’ ages are only counted where the father is named on the birth registration. Shown for context.

Source: ONS, births in England and Wales, 2025 registrations, table 11.