This is a prospective multicentric study including six clinical units of Gynecology and Obstetrics (5 public health hospital and one private team), one research team in clinical microbiology and one Center of Clinical investigation (CIC).

There is a correlation between premature delivery and bacterial vaginosis. So, the anomalies of vaginal flora are a potential target for the campaign against prematurity.

The main objective of this study is to achieve an objective and reproducible technique of identification and quantification by molecular biology of lactobacilla and all the other micro-organisms involved in vaginal flora anomalies.

The secondary objectives are the exhaustive culture of bacteria, the characterisation of intermediate vaginal flora and bacterial vaginosis among pregnant woman by PCR targeting the ribosomic ADN 16S coupled with clonage techniques.

The number of patient to include is 1000 (time of inclusions: 24 months). The vaginal smears will be realized until 32 weeks of gestation (Max: 3 taking of vaginal smears by patient).