Estimate the sensitivity and specificity of Quantitative Fluorescence Polymerase Chain Reaction (QF-PCR) in diagnosing Group B Strep (GBS) rectovaginal colonization during pregnancy, and follow the outcome of the mothers and infants. According to the outcome of this study,the investigator wish to determine that wether QF-PCR is an appropriate screening method for GBS in primary hospitals in China.

This is a study which include 300 pregnant women who will deliver their babies in PUMCH.

1. Obtain vaginal and rectal swab for Group B Strep (GBS) culture and Quantitative Fluorescence Polymerase Chain Reaction (QF-PCR) test between 35-37 weeks.
2. Obtain intrauterine swabs of the woman whose vaginal-rectal GBS test is positive,for both GBS culture and GBS QF-PCR.
3. Obtain rectal and pharynx swabs of the newborns of the woman whose vaginal-rectal GBS test is positive,for both GBS culture and GBS QF-PCR.
4. Blood test for GBS culture and GBS QF-PCR will be carried out to all the babies transferred to neonatal intensive care unit(NICU).
5. For all the samples that GBS culture result was not consistent with QF-PCR, We will do gene sequencing for verification.
6. Pregnant outcome will be followed such as Apgar score,neonatal pneumonia, urinary tract infection, chorioamnionitis, endometritis,sepsis, and bacteremia,It also can cause focal infections such as pneumonia, meningitis, and endocarditis.

Inclusion Criteria:

1.Singleton gestation.Pregnant women between 35-37 weeks gestation. 2.22 years of age or older. 3.Plan to deliver baby in Peking Union Medical College Hospital (PUMCH).

Exclusion Criteria:

1. Preexisting morbidity: Immunocompromised status (HIV +; malignancy; history of organ transplant; chronic steroid therapy; autoimmune disease requiring treatment during pregnancy, and other immunocompromised states); Type 1 diabetes and type 2 diabetes;congenital cardiac disease and cardiac valvular disease requiring antibiotic prophylaxis during procedure/labor; pulmonary disease; renal disease; chronic hepatic disease; inflammatory bowel disease; stomach or duodenal ulcer; bowel resection, gastric bypass, and chronic indwelling venous, bladder, or gastric catheter.
2. Multi-fetal gestation.
3. Chronic (daily) use of broad spectrum antibiotics. 4。Prolonged antibiotic use (> 7 days) in the 4 weeks prior to GBS culture screening.

5.History of infant with GBS sepsis. 6.intrauterine growth retardation(IUGR), Fetal Anomalies-major diagnosed at time of second trimester anatomy ultrasound.

Inclusion Criteria:

• 1.Singleton gestation.Pregnant women between 35-37 weeks gestation. 2.22 years of age or older. 3.Plan to deliver baby in PUMCH.

Exclusion Criteria:

• 1.Preexisting morbidity: Immunocompromised status (HIV +; malignancy; history of organ transplant; chronic steroid therapy; autoimmune disease requiring treatment during pregnancy, and other immunocompromised states); Type 1 diabetes and type 2 diabetes;congenital cardiac disease and cardiac valvular disease requiring antibiotic prophylaxis during procedure/labor; pulmonary disease; renal disease; chronic hepatic disease; inflammatory bowel disease; stomach or duodenal ulcer; bowel resection, gastric bypass, and chronic indwelling venous, bladder, or gastric catheter.

  2.Multi-fetal gestation. 3.Chronic (daily) use of broad spectrum antibiotics. 4.Prolonged antibiotic use (> 7 days) in the 4 weeks prior to GBS culture screening.

  5.History of infant with GBS sepsis. 6.IUGR, Fetal Anomalies-major diagnosed at time of second trimester anatomy ultrasound。 7.Anticipated delivery <35 wks for maternal/fetal indication 8.Placenta previa or accreta (with anticipated delivery prior to 35 weeks)

Inclusion Criteria:

• 1.Singleton gestation.Pregnant women between 35-37 weeks gestation. 2.22 years of age or older. 3.Plan to deliver baby in PUMCH.