At the intersection of the private sphere of the household and the public sphere of the labour market and paid work lie four essential human realities: pregnancy, childbirth, breastfeeding and childrearing. Do these factors make women unattractive as workers and cause them to be discriminated against in the labour marketplace? This study sets out to answer this question through an in-depth analysis of theory and actuality in the European Union, providing detailed analysis of EC legal measures and ECJ case law. The author's conclusions are bolstered by a revealing comparison with similar legislation and jurisprudence in the United States. The focus of the study is on the relatively narrow area of sex discrimination - discrimination because of the biological factors of pregnancy, childbirth and breastfeeding. The author demonstrates that an understanding of this specific and measurable kind of discrimination is the first step toward discrediting the wider category of gender discrimination, which penalizes women as full-time caregivers who cannot be relied upon as workers in the marketplace.