The goal of this cross-sectional study was to assess the correlation between periodontal conditions of pregnant women and characteristics of the infant at birth. One hundred thirteen pregnant patients received a thorough dental and periodontal examination and questionnaire. Probing depth (PD), clinical attachment level (CAL), bleeding on probing (BOP), and calculus index (CI) were recorded. Patients were classified as to whether they had periodontitis (presence of 2 or more teeth with 1 or more sites experiencing CAL > or = 3 mm and PD > or = 4 mm at the same site), gingivitis (> or = 25% of sites with BOP), or healthy periodontium. Patients were followed to ascertain information on pregnancy-related complications, gestational age, and birth weight. Miscarriages and infants born as single births at < 37 weeks or weighing < 5.5 pounds were classified as preterm low birth weight (PT/LBW) infants. The periodontal clinical parameters were compared between groups using the Kruskal-Wallis test and the Wilcoxon rank sum test. Spearman rank correlation coefficients were calculated to estimate the correlations. Of the 113 pregnant patients, outcome data were available on 111 patients. In addition, data from one patient who delivered twins and two patients who had miscarriages were not considered in the correlation analyses. The prevalence of periodontitis and gingivitis in this population was 23.9% and 54%, while the prevalence of PT/LBW infants was 19%, 7%, and 13% among the patients with periodontitis, gingivitis, and healthy periodontium, respectively. Given the small number of patients with PT/LBW infants, we were unable to identify any statistically significant associations between the periodontal clinical parameters and PT/LBW, although the data suggested the trend that patients with PT/LBW infants were more likely to have poorer probing depths (median number of sites with PD > or = 4mm, 13 vs. 6; p = 0.19). Among the 108 single births, birth weight was negatively correlated with maternal mean PD in the periodontitis group (r = -0.37, p = 0.055), and the percentage of sites with BOP in the mandible (r = -0.32, p = 0.014), total CL (r = -0.31, p = 0.01 7) and maxillary arch CI (r = -0.29, p = 0.025) in the gingivitis group. Infant birth weight showed moderate relationships with maternal periodontal conditions in subjects with periodontal diseases.