title: Pre-eclampsia rates in the United States, 1980-2010: age-period-cohort analysis.
abstract: OBJECTIVE
  To estimate the contributions of biological aging, historical trends, and birth cohort effects on trends in pre-eclampsia in the United States.
  
  
  METHODS
  Population based retrospective study.
  
  
  METHODS
  National hospital discharge survey datasets, 1980-2010, United States.
  
  
  METHODS
  120 million women admitted to hospital for delivery.
  
  
  METHODS
  Temporal changes in rates of mild and severe pre-eclampsia in relation to maternal age, year of delivery, and birth cohorts. Poisson regression as well as multilevel age-period-cohort models with adjustment for obesity and smoking were incorporated.
  
  
  RESULTS
  The rate of pre-eclampsia was 3.4%. The age-period-cohort analysis showed a strong age effect, with women at the extremes of maternal age having the greatest risk of pre-eclampsia. In comparison with women delivering in 1980, those delivering in 2003 were at 6.7-fold (95% confidence interval 5.6-fold to 8.0-fold) increased risk of severe pre-eclampsia. Period effects declined after 2003. Trends for severe pre-eclampsia also showed a modest birth cohort effect, with women born in the 1970s at increased risk. Compared with women born in 1955, the risk ratio for women born in 1970 was 1.2 (95% confidence interval 1.1 to 1.3). Similar patterns were also evident for mild pre-eclampsia, although attenuated. Changes in the population prevalence of obesity and smoking were associated with period and cohort trends in pre-eclampsia but did not explain the trends.
  
  
  CONCLUSIONS
  Rates of severe pre-eclampsia have been increasing in the United States and age-period-cohort effects all contribute to these trends. Although smoking and obesity have driven these trends, changes in the diagnostic criteria may have also contributed to the age-period-cohort effects. Health consequences of rising obesity rates in the United States underscore that efforts to reduce obesity may be beneficial to maternal and perinatal health.
authors.affiliation: Department of Obstetrics and Gynecology, College of Physicians and Surgeons, Columbia University, 622 West 168th Street, New York, NY 10032, USA.
authors.forename: Cande V
authors.initials: CV
authors.lastname: Ananth
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Keyes
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wapner
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology*; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D055815:Young Adult