Pre-eclampsia rates in the United States, 1980-2010: age-period-cohort analysis

BMJ. 2013 Nov 7:347:f6564. doi: 10.1136/bmj.f6564.


Objective: To estimate the contributions of biological aging, historical trends, and birth cohort effects on trends in pre-eclampsia in the United States.

Design: Population based retrospective study.

Setting: National hospital discharge survey datasets, 1980-2010, United States.

Participants: 120 million women admitted to hospital for delivery.

Main outcome measures: 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.

MeSH terms

  • Adolescent
  • Adult
  • Aging / physiology
  • Female
  • Humans
  • Maternal Age*
  • Middle Aged
  • Obesity / epidemiology*
  • Pre-Eclampsia / epidemiology*
  • Pregnancy
  • Prevalence
  • Retrospective Studies
  • Risk Factors
  • Smoking / epidemiology*
  • United States / epidemiology
  • Young Adult