Changes in trends over time for the specific contribution of different risk factors for pre-eclampsia

The prevalence of risk factors for pre-eclampsia has changed over time; however, little is known regarding how these changes have altered the specific contribution of each risk factor. We aim to identify trends in the contribution of different risk factors throughout different time intervals.

We compared the prevalence and odds-ratio of different known risk factors for pre-eclampsia occurring in three equal population groups from 1988 to 2014. Data was retrieved from our medical center's perinatal database. A multivariable logistic regression model was employed to identify independent risk factors for pre-eclampsia. We evaluated changes in risk factors and their specific contribution to the occurrence of pre-eclampsia over time and a comparison of the prevalence and odds-ratios of chosen risk factors between the three time periods was performed.

295,946 pregnancies met the inclusion criteria; of those, 16,246 (5.5%) were complicated with pre-eclampsia with the incidence increasing from 8 to 11%. Chronic hypertension, systemic lupus erythematosus, pre-gestational diabetes mellitus, twin pregnancy, advanced maternal age and fertility treatments were found to be the strongest independent risk factors. While rates of twin pregnancies and pre-gestational diabetes mellitus have demonstrated a linear increase, fertility treatments demonstrated a linear decrease. Chronic hypertension and systemic lupus erythematosus resulted in a mixed trend.

In our study, not only did the rates of different risk factors for pre-eclampsia change over the study period, the specific contribution of each risk factor for the occurrence of pre-eclampsia changed as well. Developing a better understanding of these trends might aid in our ability to predict this major complication and to improve maternal and fetal outcomes.