Among several factors in preterm low birth weight, we can find pre-conceptional causes and others depending on pregnant women's behaviour. In 1996 a scientific team composed by periodontists, gynaecologists and epidemiologists found that 18% of preterm low birth weight in 250,000 babies are due to periodontal infection. In our survey we used 113 pregnant women in gynaecological clinic in university hospital. By using Community Periodontal Index Treatment Needs (CPITN) in pregnant woman and by weighting babies as soon as accouchement done. In spite of percentage of preterm low birth weight, we registered 33.9% babies of normal birth weight with mother's CPITN under 1.