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Objective To evaluate the accuracy of realtime polymerase chain reaction (PCR) assay in the detection of group B Streptococcus (GBS) in pregnant women. Methods Samples were collected from 1 395 women at 35-37 weeks of gestation from March 1 to December 31, 2009 at three hospitals in Beijing. Samples were obtained from the lower one third vaginal wall and perianal area and tested for GBS using standard culture and PCR. Standard culture and gene analysis for GBS were applied as the gold standard, and the sensitivity and specificity of the rapid assay were determined. Results Of the 1 395 women qualified for PCR testing, 40(2.9%) were identified as GBS positive on the basis of the results of specimen culture, compared to 114 (8.2%) on the basis of PCR assay. The culture was negative and the PCR positive in 77 patients. The results which were not in agreement using the two tests were evaluated by the gene analysis for GBS. Among the 77 samples which were GBS positive by PCR, 66 samples were determined as GBS positive by gene analysis. The sensitivity of the PCR assay was 97.2%(103/106) and specificity was 99.1%(1 278/1 289), the maternal GBS colonization was 7.6%(106/1 395). Conclusions Realtime PCR assay allows rapid and reliable detection of GBS in last trimester with high sensitivity and specificity.
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Objective To study the value of cervical length(CL) by transvaginal sonography in the mid-trimester and late-trimester for the prediction of preterm delivery.Methods The CL was measured by transvaginal sonography for 5277 pregnant women between 22-24 weeks and 28-32 weeks gestation,who were prenatal cared and delivered at the First Hospital of Peking University from June 2008 to November 2009.The pregnancy outcomes were followed,and the relationship between CL and preterm delivery and preterm premature rupture of membrane was studied.Results ( 1 ) The incidence of preterm delivery was 5.4％ (289/5370) total,among of them the incidence of therapeutic preterm delivery was 1.7％ (93/5370),spontaneously preterm delivery was 1.2％ (62/5370),and preterm premature rupture of membrane was 2.5 ％ (134/5370).There are 4 cases (4/5370) who occured late abortion.(2) Excluding the 93 women who had therapeutic preterm delivery,the mean CL of 22-24 weeks was ( 38.8±4.0) mm.The relative risk for preterm delivery when the CL＜30 mm was 5.2,when CL＜25 mm,the relative risk was 11.1,and when CL ＜15 mm the relative risk for preterm delivery was 13.8.The average CL during 28-32 weeks of gestation was ( 34.6±4.8) mm,was significantly shorter than that of 22-24 weeks ( P＜0.05 ).During this period the relative risk for preterm delivery when the CL＜30 mm was 6.9,when CL＜25 mm,the relative risk was 11.1,and when CL＜15 mm the relative risk for preterm delivery was 20.0.(3) A CL＜30 mm as the cutoff value for predicting preterm delivery during 22-24 weeks of gestation has only a 3％ sensitivity and 19％ positive predictive value,but had a 99％ specificity and 96％ negative predictive value.The sensitivity,positive predictive value,specificity and negative predictive value for a CL ＜ 30 mm as the cut-off value for predicting preterm delivery during 28-32 weeks of gestation was 33％,21％,95 ％ and 97 ％ respectively.(4) The total number of preterm premature rupture of membrane pregnant women was 134 (2.5％ ),who had a mean CL of (38.4 ±4.7) mm during 22-24 weeks of gestation,was similar with the women without preterm premature rupture of membrane ( PPROM),but during 28-32 weeks of gestation the women who occured PPROM had a mean cervical length of ( 30.6 ± 8.1 ) mm,and was significantly shorter than that of women without PPROM ( 34.7 + 4.6 ) mm.Conclusions ( 1 ) CL in 28-32 weeks of gestation issignificantly shorter than that of in the mid-gestation,but more than 90％ of women has a CL≥30 mm.(2)The shorter the CL is,the greater the relative risk of preterm delivery.According to different CL for clinical consulting objective relative risk could be provide.(3) The CL during 28-32 weeks of gestation can also predict preterm delivery,the sensitivity is obviously better than that of 22-24 weeks of gestation.(4) The CL during 28-32 weeks of gestation is valuable for predicting of PPROM.
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Objective To study the sensitivity of the real-time polymerase chain reaction (RT-PCR) in detecting group B streptococcus (GBS) in late pregnant women and the influence of vaginal/rectal GBS colonization on maternal and neonatal outcomes. Methods Microbiological culture and RT-PCR for GBS were both performed for each sample taken from the vagina and rectus in 617 gravidas at 35-37 weeks of gestation, with an average age of 30.1, among which 80 aged over 35. Forty-one out of the 617 women were multiparous and 576 primiparous. The laboratory results were collected and the pregnant outcomes were followed. Results (1) Out of the 617 gravidas, 21 (3.4%) were GBS positive by culture (all positive in RT-PCR) and 57 (9.2%) were GBS positive by RT-PCR. Thirth-six cases with PCR positive but culture negative results were analyzed by sequencing, and 34 showed GBS positive and 2 negative. (2) The sensitivity and specificity of RT-PCR was 100% (55/55) and 99.6% (560/562) respectively. (3) The average age of GBS positive gravidas was 30 ± 4, without significant difference compared with that of GBS negative women (31±4), P>0.05. The GBS positive rates were also similar between the primiparas and the muliparous [7.3% (3/41) vs.9.4% (54/576)] , between elderly women and those under the age of 35, and between those women who had abortions over and less than 3 times (all P>0.05). (4) No significant difference was found in the cesarean section rate between the GBS postitive and negative group [54.4% (31/57) vs.44. 6% (250/560), P>0.05]. (5) Compared with the GBS negative group, the GBS positive group had higher incidence of intrauterine infection [6.6% (37/560) vs. 15.8% (9/57)], postpartum hemorrhage (2.9% vs.10.5%) and fetal distress (25.9% vs. 38.6% ) all P <0.05, but had similar incidence of premature rupture of membranes [25.0% (140/560) vs. 33.3% (19/57) ], pretcrm birth and meconium-stained amniotic fluid. (6) The neonatal infection rate in the GBS positive group was significantly higher than that of the GBS negative group [29.8% (17/57) vs. 13.2% (77/560), P < 0.05]. One neonate in the GBS positive group developed early-onset severe GBS infection and achieved better outcome under proper treatment. Conclusions Maternal GBS carrier at 35-37 weeks of gestation can lead to adverse pregnant outcomes by increasing the incidences of intrauterine infection and neonatal infections. However, RT-PCR could be a routine method to detect GBS status in late pregnant women with its higher sensitivity and specificity.