Background: Pre-term delivery is still a main cause of perinatal mortality and morbidities. This study was designed to find any association between maternal Group B Streptococcus (GBS) colonization and pre-term delivery. Method: This case-control study was conducted from March 2010 to May 2011 at two referral university hospitals (Al-Zahra and Shaheed Beheshty), Isfahan University of Medical Sciences, Isfahan, Iran. The study sample of pregnant women was composed of a control group of 200 term pregnancy with at least 37 complete weeks, and a case group of another 200 women between 20 to 37 weeks of pregnancy with pre-term labor. Maternal GBS colonization was compared between two groups. Results: Maternal age (26.03±4.81 vs. 27.19±5.60, P=0.07) and gravid (1.75±0.88 vs. 1.83±1.08, P=0.52) were similar in case and control groups. Level of education and gestational age were significantly higher in control versus case group (P=0.01, P=0.00). History of antibiotic use during pregnancy was more frequent in case group compared with control group (P=0.00). There were 59/151 (39.1%) positive vaginal samples in case group compared with 36/178 (20.2%) in control group (P=0.000). There were 55/151 (36.4%) positive rectal samples in case group versus 30/178 (16.9%) in control group (P=0.000). Conclusion: This study showed that GBS colonization was statistically higher in pre-term labors compared with term deliveries. To understand the mechanism of GBS effect on pregnancy, large observational studies are needed, with clearly defined outcomes, and with prognostic risk factors for pre-term delivery taken into account.
Pre-term Labor; Group B Streptococcus; Recto vaginal.