[Determinants of group B streptococcus maternal colonization and factors related to its vertical perinatal transmission: case-control study].

OBJECTIVES: To investigate the determinants of Group B streptococcus (GBS) maternal colonization, as well as factors associated with its vertical transmission. PATIENTS AND METHODS: Case-control study on all singletons pregnancies delivered beyond at least 24 weeks of amenorrhoea in Southern Reunion maternities for which GBS screening was known. Multiple logistic regression analysis using 2004-2007 dataset of South Reunion birth registers.
RESULTS: Out of 17,430 women delivered between 1st January 2004 and 31st December 2007, 2911 (16.7%) carried GBS. In a model adjusted on antenatal care, risk groups for GBS carriage were the women indigenous from another island of the Indian Ocean than Reunion (OR: 1.29, CI95%: 1.05-1.57) and obese women (body mass index ≥ 30, OR: 1.19, CI95%: 1.03-1.18). Protective factors included birthplace in mainland France (OR: 0.82, CI95%: 0.69-0.97) and underweight (OR: 0.81; CI95%: 0.69-0. 95). In a model controlling for a composite obstetrical variable delineating the protective roles of C-section and antibioprophylaxis as well as the putative role of meconium-stained fluids (thin, thick or fetid), all previously found in our setting, three key factors were independently associated with GBS vertical mother-to-child transmission: obesity (OR: 1.48, CI95%: 1.05-2.09), fetal tachycardia (OR: 4.92, CI95%: 2.79-8.68) and late preterm birth (35 to 36 wks, OR: 2.14, CI95%: 1.32-3.45).
CONCLUSION: These findings strengthen the putative roles of corpulence and ethnicity in GBS acquisition previously found in the United States, while confirming an authentic role of obesity in its vertical transmission, independently of other classical cofactors lighted by our study.