Educational differences in completed fertility – a study of Finnish twins

Jessica Nisén, University of Helsinki
Pekka Martikainen, University of Helsinki
Jaakko Kaprio, University of Helsinki
Karri Silventoinen, University of Helsinki

Association between educational level and number of children has been studied widely, at least for women. However, the contribution of family background for this association has received less attention. This study aimed to quantify the educational differences in completed fertility for men and women in Finland and to examine in a twin setting whether family background could contribute to these differences. The data consisted of 3592 male and 4228 female same-sex Finnish twins born in 1950–57 – derived from the Finnish Twin Cohort Study. For level of education we used survey information collected in 1975/1981. Register-based information on fertility was linked to the survey data until 2009. Multinomial logistic regression analysis was used to study twins as individuals and conditional logistic regression analysis in order to study discordant twin pairs. Men who had only primary school education (the lowest education category used as the reference group) were less likely than men in other educational groups to have both one to two (1–2) and at least three (3+) children as compared to childlessness (OR 1.00 vs. 1.32–1.75 and OR 1.00 vs. 1.38–1.61, respectively). In women those belonging to the senior high school (or more) educated groups were less likely to have both 1–2 children and 3+ children than women in primary school educated groups (OR 0.58–0.63 vs. 1.00–1.07 and OR 0.51–0.58 vs. 0.91–1.00, respectively). Within discordant male twin pairs there was evidence for an educational gradient similar to that of the twin individual analysis. For women the pair-wise analysis showed hardly any association. These results suggest that family background might play a role in the female association whereas for men the association seems more likely to result from a causal relationship between education and fertility.