(1060) Concordance of maternal GBS DNA-PCR rectovaginal test at 36 weeks and maternal/neonatal testing at delivery

Objective: GBS is an important cause of neonatal infectious morbidity. Universal GBS screening via rectovaginal test in the late third trimester, with intrapartum antibiotic prophylaxis if GBS positive, decreases the risk of neonatal GBS infection. The effectiveness of this strategy depends on the predictive nature of this result, and GBS point-of-care (POC) testing at the time of delivery admission has been proposed as a possible strategy to further decrease neonatal risk. The goal of this study was to determine discordance between a negative GBS test at 36 weeks and at the time of delivery using GBS DNA-PCR.

Study Design: Prospective pilot study of pregnant persons with a negative GBS DNA-PCR rectovaginal test on routine screen at 36 weeks intending to deliver vaginally at the study institution from 3/2023-4/2024. On admission for delivery, repeat maternal rectovaginal GBS DNA-PCR was performed; immediately after delivery, GBS DNA-PCR testing was performed on the placenta and neonatal ear. Results were not disclosed to the clinical team and intrapartum/neonatal care was otherwise routine. Primary outcome was GBS positive rate. Planned sample size was 60. Study supported by an institutional grant.

Results: 39 patients were enrolled; 9 did not complete the study (tests not performed as planned, subject withdrew or delivered elsewhere) for 30 completed subjects. Recruitment was terminated early due to slow enrollment. Most subjects were White (80.0%), non-Hispanic (86.7%), and multiparous (60.0%), Table. Mean gestational age at delivery was 40.3±0.68 wks and 93.3% delivered vaginally. Of the 90 GBS DNA-PCR study tests performed, 2/90 (2.2%) were positive in 2 different patients – 1 maternal rectovaginal and 1 neonatal ear – for a GBS positive rate of any result in 2/30 (6.7%) patients. There were no cases of neonatal GBS sepsis.

Conclusion: Maternal and neonatal GBS DNA-PCR testing results done at 36 weeks and at the time of delivery are highly concordant. Our findings suggest that the addition of GBS POC testing at the time of delivery admission is likely low yield and would add additional cost.