Prenatal screening provides a good illustration of the tensions existing between the intention of control associated with standard risk surveillance and the permanence of uncertainty around life processes. During the screening process, health professionals and pregnant women are not only confronted with the limitations of probabilistic thinking, they are also concretely reminded of the extent of uncertain outcomes. We analysed such tensions, emblematic of the notion of manufactured uncertainty (Giddens 1994), with qualitative data collected in Switzerland from both gynaecologists and mothers-to-be. Doctors experienced difficulties in regards to expectations raised by risk surveillance, the duty to inform and the anxiety surveillance induced. Pregnant women coped in different ways with probabilistic thinking, developing contrasting responses to uncertainty, ranging from scepticism about risk thinking to aspiration for control leading to over use of medical procedures. As uncertainty was central to professional and lay thinking both made use of subjective interpretations and cultural meanings in decisions related to future events.