Objective: To investigate the impact of maternal age on singleton pregnancy outcome, taking into account intermediate and confounding factors.
Study design: In this population-based retrospective cohort study, perinatal data of primiparous women aged 35 years or more (n = 2970), giving birth to a singleton child of at least 500 g, were compared to data of primiparous women aged 25-29 years old (n = 23,921). Univariate analysis was used to assess the effect of maternal age on pregnancy outcomes. The effects of intermediate (hypertension, diabetes and assisted conception) and confounding factors (level of education) were assessed through multivariable logistic regression analysis.
Results: Older maternal age correlated, independently of confounding and intermediate factors, with very preterm birth (gestational age <32 weeks) [adjusted odds ratio (AOR) 1.51, 95% confidence intervals (CI) 1.04-2.19], low birth weight (birth weight <2500 g) (AOR 1.69, 95% CI 1.47-1.94) and perinatal death (AOR 1.68, 95% CI 1.06-2.65).
Conclusion: Maternal age is an important and independent risk factor for adverse pregnancy outcome.