Maternal serum levels of the first- and second-trimester markers for aneuploidy have been shown to be associated with adverse obstetric outcomes in the absence of aneuploidy or neural-tube defects. The likelihood of an adverse obstetric outcome increases as the values of the marker become more extreme, and as the number of abnormal markers increases. Although many of the associations between maternal serum markers for aneuploidy and adverse obstetric outcomes are statistically significant, the sensitivity and positive predictive values for the individual outcomes are too low for them to be clinically useful as screening tests. Currently in the United States there is not a uniformly accepted practice for the care of women with abnormal maternal serum markers regarding risk of future obstetric complications. There are no randomized trials assessing any type of intervention or treatment for patients with abnormal serum markers. Various strategies to manage patients with unexplained abnormal serum markers have been proposed. This article reviews the relationships between these markers and adverse obstetric outcomes. In addition, potential management strategies and future areas of research are discussed.