Universal screening for gestational diabetes mellitus (GDM) has been a topic of ongoing controversy for many years. In 2005, the French Health Authority concluded that no recommendation could be issued because of insufficient evidence. Recently, several studies have clarified the issues. It is now clearly established that women with GDM, including mild forms, are at increased risk of perinatal complications. Randomized controlled trials demonstrate that treatment to reduce maternal glucose levels improves perinatal outcomes. Today, the rationale for screening appears unquestionable. There are simple screening tests. However, it remains difficult to define threshold values because there is a strong, continuous association of maternal glucose levels with increased risks of adverse pregnancy outcomes.