The purpose of this study is to begin to apply the findings of the ongoing exercise in pregnancy project to demographically high risk populations to test the hypothesis that beginning a regular exercise regimen will decrease risk and improve outcome. We will be studying two at risk populaces who are at the extremes of reproductive life: a group of young, primigravid or secundigravid, low income, urban women and a group of primigravid women over the age of 36. In both groups, the risks of pregnancy are increased.