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).

Inclusion Criteria:

• Pregnant patients aged more than 18 years and more than 14 weeks of gestation but less than 28 weeks.
• Multiple pregnancy won't be included.
• Patient with a risk of premature delivery with a short cervix or a cervix measured at less than 25 mm (measure done by vaginal ultrasound of the cervix).
• Or patient with a past of premature delivery and/or of late abortion.
• Symptomatic or asymptomatic patient.
• Patients consulting for pregnancy follow up or hospitalized in a unit of Gynecology and Obstetrics involved in the study.
• social security cover
• written informed consent

Exclusion Criteria:

• antecedents : treated hypertension, Foetal malformation, APLS known, diabetes, renal disease, SLE
• treated with antibiotics the inclusion's day
• dropping consent.