text: Background: Few studies have reported on population-level incidence of or trends in the hypertensive disorders of pregnancy, and none report on data through 2004. We describe population trends in the incidence rates of preeclampsia, eclampsia, and gestational hypertension in the United States for 1987-2004.
  Methods: We analyzed public-use data from the National Hospital Discharge Survey (NHDS), which has been conducted by the Centers for Disease Control and Prevention, National Center for Health Statistics since 1965. We calculated crude and age-adjusted incidence rates and estimated the risk associated with available demographic variables using Cox regression modeling.
  Results: Rates of preeclampsia and gestational hypertension increased significantly (by 25 and 184%, respectively) over the study period; in contrast, the rate of eclampsia decreased by 22% (nonsignificant). Women under the age of 20 were at significantly greater risk for all three outcomes. Women in the south of the country were at significantly greater risk for preeclampsia and gestational hypertension when compared to those in the Northeast.
  Conclusions: The increase in gestational hypertension may be exaggerated because of the revised clinical guidelines published in the 1990s; these same revisions would likely have reduced diagnoses of preeclampsia. Therefore, our observation of a small but consistent increase in preeclampsia is a conservative indication of a true population-level change.