Preeclampsia Mediates the Association between Advanced Maternal Age and Adverse Pregnancy Outcomes: A Structural Equation Modeling Approach

Background: Advanced maternal age (AMA) is considered a risk factor associated with preeclampsia and adverse pregnancy outcomes. We aimed to assess the mediating role of preeclampsia between AMA and adverse pregnancy outcomes. Methods: A sample of 14646 pregnant women from the tertiary hospital of Hubei Province, China, during the years 2011-2017 were included in this study. Pregnant women were divided into 4 groups according to their age at delivery. Mediated effect of preeclampsia with relation to AMA and adverse pregnancy outcomes was measured using structural equation modeling. Results: Women in the highest age group were significantly associated with preterm delivery [RR 1.37 (95% CI 1.24 - 1.49)] and low birth weight [RR 1.28 (95% CI 1.11 - 1.45)] compared with women in the lowest age group. The indirect effect (mediated effect) of AMA on preterm delivery and low birth weight mediated by preeclampsia was [beta 0.053 (95% CI: 0.047, 0.060)], and [beta 0.045 (95% CI: 0.038, 0.052)], respectively. The estimated mediation proportion of the effect of AMA due to mediated effect of preeclampsia was (35.5%) for pre-term delivery and (23.5%) for low birth weight. Conclusion: Preeclampsia partially mediates the association between AMA and adverse pregnancy outcomes.