One of the major corollaries of the post-war fertility boom and decline is that two-child families became common across Europe after the 1970s. Despite the general agreement on the convergence of fertility trends, there is still little understanding of how this change took place in a comparative perspective of Western and Eastern Europe, which at that time were characterised by Cold War tensions of different ideological regimes. This study addresses this aspect by focusing on individual decisions around childbearing, child-rearing and family size. Based on 104 oral histories from Switzerland and Ukraine, this study illuminates that the urban setting provided parents with a similar set of constraints and opportunities, which eventually resulted in strikingly similar perceptions of the costs of childrearing on two sides of the Iron Curtain. Individuals’ motives to postpone first birth in Switzerland and second birth in Ukraine rested on a similar aspiration to invest in the well-being of children by ensuring material security for the family. This aim was increasingly achieved through female labour-force participation and adoption of modern contraception – the pill in Switzerland and abortion in Ukraine. While the timing of returning to the labour market and the share of women working after entering parenthood might have varied across the two contexts, a good mother became increasingly defined in both contexts in terms of providing emotionally and financially for her children. Although the introduction of modern birth control methods allowed couples to plan family size more carefully, it also made Swiss and Ukrainian women increasingly carry the major costs and actual burden of birth control. Altogether, this study challenges the common assumption around the persistence of strikingly different demographic realities in post-war Western and Eastern Europe by uncovering the mechanisms behind the stabilisation of family size around the two-child family ideal.