- Objective: To determine the risk factors and pregnancy outcome of patients with chronic hypertension during pregnancy after controlling for superimposed preeclampsia. Method: A comparison of all singleton term (>36 weeks) deliveries occurring between 1988 and 1999, with and without chronic hypertension, was performed. Stratified analyses, using the Mantel–Haenszel technique, and a multiple logistic regression model were performed to control for confounders. Results: Chronic hypertension complicated 1.6% (n=1807) of all deliveries included in the study (n=113 156). Using a multivariable analysis, the following factors were found to be independently associated with chronic hypertension: maternal age >40 years (OR=3.1; 95% CI 2.7–3.6), diabetes mellitus (OR=3.6; 95% CI 3.3–4.1), recurrent abortions (OR=1.5; 95% CI 1.3–1.8), infertility treatment (OR=2.9; 95% CI 2.3–3.7), and previous cesarean delivery (CD; OR=1.8 CI 1.6–2.0). After adjustment for superimposed preeclampsia, using the Mantel–Haenszel technique, pregnancies complicated with chronic hypertension had higher rates of CD (OR=2.7; 95% CI 2.4–3.0), intra uterine growth restriction (OR=1.7; 95% CI 1.3–2.2), perinatal mortality (OR=1.6; 95% CI 1.01–2.6) and post-partum hemorrhage (OR=2.2; 95% CI 1.4–3.7). Conclusion: Chronic hypertension is associated with adverse pregnancy outcome, regardless of superimposed preeclampsia.