It is well established that family formation has negative consequences on women’s wages, while men are unaffected or even gain a bonus. Identifying possible explanations, the “how” and “why” this family gap comes about, has been paramount in the literature. Hereby, I address the question of “when” exactly does parenthood affect wages differentially for women and men, relying on panel data for the UK (BHPS and UKHLS) and Germany (G-SOEP) spanning more than two decades. With a focus on the period preceding first childbirths, I examine whether parents-to-be anticipate the event by changing their labour supply behaviour, self-select into parenthood on the basis of prior wages, or – in the case of women – if they are statistically discriminated. Using both conventional fixed-effects and a difference-in-differences design, I find evidence supporting a scenario of statistical discrimination in Germany, and less so in the UK, as the wages of both mothers-to-be and childless women are pulled down during prime-childbearing years and regardless of realised fertility. For fathers evidence is less clear-cut, pointing at both self-selection on the basis of prior wages and discrete wage spikes (of around 1-2%) the year after each childbirth event. The question of “when” is also declined in terms of change across cohorts: in both countries, motherhood wage penalties seem to have progressively worsened (-40% after ten years from the event in Germany, -30% in the UK). Such a change is not accounted for by differential selectivity into employment across cohorts.