[Detection of maternal colonization of group B streptococcus in late pregnancy by real-time polymerase chain reaction and its effect on perinatal outcome].

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. Thirty-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 multiparous [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 positive 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)], preterm 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.