The idea that a motherís psychological state can negatively influence the outcome of pregnancy and the health of her unborn child has been deeply ingrained into many societies since the beginning of modern civilisation. This concept was revived in the twentieth century when a series of large-scale, manmade and natural disasters, such as war and famine, coupled to population level data, provided an opportunity to examine the effect of stress during pregnancy on the subsequent mental and physical health of the unborn infant. The establishment of the Scandinavian registers, such as those in Sweden and Denmark, has facilitated a closer examination of the effect of antenatal maternal stress on subsequent offspring outcomes at an individual level. There is now a considerable body of work to support the hypothesis that maternal psychological stress in the peri-conception and antenatal period is associated with a diverse range of adverse outcomes for the offspring, including immediate obstetric complications and later psychiatric disorders and chronic physical ill-health. Here we discuss the most recent and robust data emanating from Scandinavian Register-based research programmes and contemporary birth cohorts. We provide evidence that psychological stress is associated with a range of adverse outcomes, which in some cases are gender specific. Moreover, we provide evidence that the timing of exposure is critical and provides tantalising clues into the potential underlying causal pathways.