An article examined the relationship between age norms and second birth rates in 23 European countries. It considered whether ideas about the 'proper' age for parenthood interacted with actual ages at first birth in influencing second birth transitions. In regions with older ideal ages for parenthood, the second birth rate was depressed for women with young ages at first birth, and vice versa. This effect, however, was strongly reduced and remained only marginally significant after controlling for an interaction between regional gross domestic product and age at first birth – suggesting that rich regions exhibited weaker postponement effects, and that this relationship largely absorbed the effect of age norms. The negative effect of high age at first birth on the second birth rates also attenuated with educational attainment.
Source: Jan Van Bavel and Natalie Nitsche, '"The proper age for parenthood" and second birth rates in Europe', European Sociological Review, Volume 29 Number 6