The main objective of this study : Demonstrate that GBS (group B streptococci) "ST-17" colonize and persist to 60 days twice in the digestive tract of newborns that strains of GBS non-ST-17.

Secondary objectives:Determine:

• The frequency of colonization with GBS ST-17 and GBS non-ST-17 of at risk pregnant women.
• The frequency of colonization of neonates by GBS ST-17 at birth.
• The preferential site of colonization in the mother (rectum, vagina, breast milk).
• The kinetics of colonization after birth in the newborn.
• The sensitivity and specificity of different GBS detection methods (conventional phenotypic versus molecular) in the different types of samples from the mother and the newborn.

Women tested positive for GBS during systematic vaginal screening at 35-37 weeks, will be proposed to participate to the study and will be included after reading the information letter and signature the consent form.

INCLUSION (D0 at time of delivery)

In the labor ward, two women's groups 1 and 2:

Group 1 = Women tested positive for GBS pre-selected and included in the protocol (see pre-inclusion) Group 2 = Women without antenatal vaginal screening and at risk of neonatal infection.

For both groups, at time of delivery:

At the beginning of the labour performed vaginal swabs (PV0):

• one swab for GBS detection by real-time PCR using the Cepheid technique conducted in the labor ward by the midwife.
• the second swab for GBS detection by conventional bacteriological techniques and sent to the bacteriology laboratory.

For all women included (Group 1 and Group 2 women with a positive GBS vaginal sample) will be achieved in the delivery room:

1. To the mother: A blood sample of 5 ml at the time of the implementation of the IV line.
2. A sampling of umbilical cord blood. Newborns of mothers included (group 1 and 2) will have a search for GBS (standard culture) in the stools and the pharynx prior to return home. Samples will be sent to the bacteriology laboratory and analyzed by classical bacteriological method (culture) and / or real-time PCR.

For mothers, the collection of 3-5 ml of milk when breastfeeding.

Monitoring schedule:

Day 21 and day 60 post delivery:

the following samples for search of GBS for will be performed to gather the primary endpoint:

For the mother:

• Vaginal sample.
• Collection of 3-5 ml of breast milk when breastfeeding

For the newborn:

• Sample collection of feces
• Swab of buccal cavity

Processing bacteriological samples:

All samples will be subjected to bacteriological analysis and DNA extraction for detection of GBS. GBS isolated will be identified and stored at - 80 ° C in a declared biological collection. DNA extracts will also stored at -20 ° C in a declared biological collection. All samples for microbiological analysis will be stored at - 80 ° C.

Inclusion Criteria:

• Patient having a positive vaginal swab for GBS at the end of pregnancy (PCR +).
• Patient aged over 18 years
• Patient who received information and agreeing to sign informed consent
• Patient affiliated or beneficiary of an insurance

Exclusion Criteria:

- Patient does not speak and does not understand French