Aim: To investigate the association between chronic periodontitis (CP) and pre-maturity in a group of Brazilian pregnant women from the State of Sao Paulo. Materials and Methods: One hundred and twenty-four women were investigated consecutively in a cross-sectional study, between December 2003 and May 2005. Sixty-eight women had pre-term labour (PTL) and 56 had term labour. A periodontal examination was carried out to identify the presence of CP. Statistical analysis used the Fisher's exact test or chi(2) for the discrete variables and the Mann-Whitney test for the non-parametric variables. Odds ratio (OR) was calculated with a 95% confidence interval (CI), to evaluate the relation between CP and pre-maturity. Results: Periodontal indicators, such as clinical attachment loss (p < 0.0001) and bleeding on probing (p=0.012), were observed more in the PTL group. The presence of CP increased the risk for PTL (OR: 4.7, 95% CI: 1.9-11.9), pre-term birth (PTB; OR: 4.9, 95% CI: 1.9-12.8) and low birth weight (< 2500 g; OR: 4.2, 95% CI: 1.3-13.3). The pregnant women with PTL presented low levels of schooling (p=0.029) and the lowest number of pre-natal appointments (p=0.0001) when compared with those with term labour. Conclusion: CP is strongly associated with PTL, PTB and low birth weight in a group of Brazilian pregnant women. These data point to the necessity of regularly investigating CP during pregnancy.343208213