OBJECTIVES: Recent studies have suggested that periodontal disease is a risk factor for low birth weight (LBW) with other multiple factors. A cross-sectional study was undertaken to help further evaluate the proposed association between periodontal disease and infant birth weight. MATERIAL AND METHODS: Caucasian pregnant women (n=152), aged 14-39 years, were enrolled while receiving prenatal care. Dental plaque, probing depth, bleeding on probing and clinical attachment level were recorded and three groups were made: healthy group (HG) (n=38), gingivitis group (GG) (n=71) and periodontitis group (PG) (n=43). At delivery, birth weight was recorded. RESULTS: Infant mean weight at delivery was 3293.9+/-508.1 g. The total incidence of preterm birth and LBW infants was 5.3% and 4.6%, respectively. The incidence of LBW infants was 3.5% in term gestations and 25% in preterm gestations. Mothers height correlated with infant birth weight (p=0.03). Significant difference in birth weight existed between mothers with <1.55 m (3229.23+/-462.57) and those with > or =1.65 m (3475.55+/-505.07). In the group of women >25 years old infant mean weight in HG was 3588.33+/-531.83, being lower in GG (3466.75+/-334.45) and even lower (3092.60+/-592.94) in PG (p=0.0198). Bleeding on probing was significantly greater in women with <2500 g infants (40.2+/-21.8%) compared with 2500-3499 g (18.6+/-15.1%) and > or =3500 g (17.1+/-16.1%) (p=0.009). CONCLUSIONS: Periodontal disease in normal Caucasian pregnant women, older than 25 years, is statistically associated with a reduction in the infant birth weight. These data provide new evidence on the relationship between periodontal disease and birth weight.