Improvement of selection of pregnant women for intrapartum polymerase chain reaction screening for vaginal Group B Streptococci (GBS) colonization by adding GBS urine screening at 35-37 weeks of pregnancy.

Objective: To evaluate whether systematic antepartum screening for Group B Streptococci (GBS) by urine culture improves the risk factor-based selection of pregnant women for intrapartum GBS screening with a rapid polymerase chain reaction (PCR) assay.

Methods: A prospective observational study was conducted between April 2013 and June 2014. GBS colonization judged by urine culture at 35-37 weeks of gestation was compared with the result of a vaginal GBS PCR test at labor as outcome. The results of urine culture were used as exposure variable. The PCR test was performed on intrapartum vaginal samples.

Results: Screening for urine GBS in 902 unselected pregnant Danish women at 35-37 weeks of gestation predicted intrapartum PCR GBS status with a sensitivity of 33.6%. A positive predictive value of 41.2% was seen among women with low GBS counts (<104 CFU/mL) and 83.3% among women with high GBS counts (≥104 CFU/mL). Systematic GBS screening of urine at 35-37 weeks of gestation added 30.9% extra women for intrapartum GBS PCR screening in the study group.

Conclusions: Systematic antepartum GBS screening of urine should be implemented in order to improve risk stratification for early onset GBS by offering laboring women an intrapartum GBS PCR test.