Objective: To evaluate the impact of gestational age on clinical laboratory findings and maternal-perinatal outcomes in patients with HELLP syndrome. Method: A retrospective review of 74 patients with HELLP syndrome between January 2007 and October 2010 was performed. Data were stratified into two groups by gestational age at the onset of disease: group 1 (< 34 weeks) and group 2 (>= 34 weeks). Clinical signs and symptoms, laboratory findings, and maternal and perinatal outcomes were evaluated. Results: No differences were observed between the two groups in the clinical and laboratory characteristics according to onset of HELLP syndrome except for gravidity, parity, and delivery interval. Maternal complications did not differ between the groups. The perinatal mortality rate was 22.9% in total and it was 43.2% in group I. Conclusions: The time of onset of the HELLP syndrome mainly affects neonatal outcomes. To assess the effect on maternal morbidity more studies are needed.