Pentraxin-3 has been reported as a promising biomarker of pre-eclampsia and its severity; however, available studies have small sample sizes, and analyses are not always adjusted for confounders. The aim of this study is to establish the strength of the association between maternal Pentraxin-3 level and pre-eclampsia or HELLP syndrome. It was a case-control study. Women with pre-eclampsia or HELLP syndrome were defined as cases, and women with healthy pregnancies at term (>37 weeks) were classified as controls. Plasma concentrations of Pentraxin-3 were determined at the time of delivery by quantitative enzyme immunoassay. Associations between Pentraxin-3 and pre-eclampsia and HELLP syndrome were assessed by multinomial logistic regression. Subsidiary analysis for the time of disease onset was also carried out. Odds ratios and 95% confidence intervals are reported. A total of 1024 pregnant women were included (461 controls, 368 pre-eclampsia, 195 HELLP). A positive log-linear relationship was found between the top pentraxin-3 quintile and HELLP syndrome. After adjustment for confounders (maternal age, ethnicity, socioeconomic position, date and place of recruitment, family history of pre-eclampsia, smoking, body mass index at beginning of pregnancy, gestational age and multiple pregnancy), the strength of the association was higher for HELLP syndrome [OR 1.13 (95% CI 1.08; 1.18)] than for pre-eclampsia [OR 1.03 (95% CI 1.03; 1.10)]. No difference according to time of onset or pentraxin-3 level was found. In summary, pentraxin-3 level was associated with pre-eclampsia, but it was more strongly associated with HELLP syndrome. Longitudinal studies with a lower probability of residual confounding are necessary to improve our knowledge about the role of pentraxin-3 in pre-eclampsia.