Point-of-care intrapartum group B Streptococcus (GBS) polymerase chain reaction (PCR) screening is associated with a significantly decreased rate of early-onset GBS disease and antibiotic use in newborns, according to a study published in Obstetrics & Gynecology.

Researchers conducted a before-and-after uncontrolled study to assess outcomes and costs associated with point-of-care intrapartum GBS PCR screening in the delivery room. Intrapartum PCR screening was implemented in 2010 in the researchers’ institution and outcomes were compared with an antenatal culture screening strategy. The study period included 4 years before (2006) and 6 years after (2015) implementation of the screening intervention. A total of 11,226 deliveries were recorded during the antenatal culture screening period (2006 to 2009)  compared with 18,835 during the intrapartum PCR screening period (2010 to 2015), corresponding to 11,818 and 18,980 live births, respectively.

Antenatal screening involved culture of a vaginal swab obtained at 35 to 37 weeks’ gestation. If the screening was positive, if women had GBS bacteriuria during the current pregnancy, or if they had a history of delivering a neonate who experienced early-onset neonatal GBS disease, intrapartum antibiotic prophylaxis was administered at the onset of labor or rupture of membranes. If GBS status was unknown at the time of delivery, intrapartum antibiotic prophylaxis was administered to women with membrane rupture > 12 hours, intrapartum fever ≥38°C, or delivery before 37 weeks’ gestation.

During the intrapartum PCR screening period, midwives performed GBS PCR screening for all term deliveries. At labor onset or after membrane rupture, the midwife performed a double vaginal swab; one side was used for the Xpert GBS PCR test in the delivery room while the other was sent to the laboratory for culture. Intrapartum antibiotic prophylaxis was administered to women who screened positive or to those presenting with the same risk factors as above.

During both study periods, intrapartum antibiotic prophylaxis was not administered for cesarean deliveries performed before labor onset in women with intact amniotic membranes. All cases of early-onset neonatal GBS disease were retrieved from the laboratory and linked to patient’s medical charts; records of newborns with GBS infection were reviewed by a neonatologist for diagnosis, clinical signs, laboratory evaluations, and number of days of antibiotic treatment.  

During the intrapartum PCR screening period, 14.5% of term deliveries screened positive for GBS compared with 12.2% during the antenatal culture period, and 91.8% of women who screened positive received intrapartum antibiotic prophylaxis compared with 89% during the antenatal culture period. In the antenatal culture period, 3.5% of term deliveries did not undergo GBS testing compared with 0.1% in the intrapartum PCR period. In both periods, penicillin G was the chosen treatment in 94.8% of cases, and approximately 50% of women received at least 2 doses.

The number of proven and probable early-onset GBS disease cases was 60% lower in the intrapartum PCR period compared with the antenatal culture screening period (3.8/1000 vs 0.9/1000, respectively). The rate of proven early-onset GBS disease cases decreased from 1.01/1000 in the antenatal culture screening period to 0.21/1000 in the intrapartum PCR period, while the rate of probable early-onset disease cases decreased from 2.8/1000 to 0.73/1000. The proportion of newborns with mothers who screened positive for GBS infection decreased from 0.86% to 0.38%, and a decrease from 1.40% to 0.28% was seen in infants born to mothers with unknown GBS status at delivery. In women who screened negative, the proportion with early-onset GBS disease dropped from 0.36% in the antenatal culture screening period to 0.04% in the intrapartum PCR period, reflecting a 78.5% decrease.

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The average cost per delivery was $2691 in the antenatal screening period and $2381 in the intrapartum screening period. The yearly cost of delivery and treatment of newborns with GBS disease was reduced from $41,875±6823 to $11,945±10,303 after the implementation of intrapartum PCR screening.

“We found that intrapartum PCR screening compared with antenatal culture screening was associated with a significant decrease in the rate of proven and probable early-onset neonatal GBS disease cases,” the authors concluded. “The decrease in early-onset neonatal GBS disease was associated with a threefold reduction in the total numbers of days of hospital and antibiotics for early-onset GBS disease.”

Reference

El Helali N, Habibi F, Azria E, et al. Point-of-care intrapartum group B Streptococcus molecular screening: effectiveness and costs. Obstet Gynecol. 2019;133(2):276-281.