Int J Gynaecol Obstet. 2013 Jul;122(1):9-12.

16 YEARS EXPERIENCE WITH GROUP B STREPTOCOCCAL SCREENING OF PREGNANT WOMEN AT 30-32 WEEKS GESTATION IN A POPULATION AT HIGH RISK FOR PREMATURE BIRTHS

BOLDIZSAR HORVÁTH, MD PhD. *, **,  MAGDOLNA GRASSELLY MD**, TAMÁS BÖDECS MD*  IMRE BONCZ MD PhD*   and  JÓZSEF BÓDIS  MD. DSc*

Faculty of Health Sciences University of Pecs *Hungary, Markusovszky Teaching Hospital Szombathely** Hungary

Please send correspondence to: drhorvathboldizsar@gmail.com

 

Abstract

Objective: The aim of this prospective study was, to confirm the benefit of instituting a GBS screening and chemoprophylaxis program at our institution where no such program previously existed, and to compare our results obtained by screening for GBS at 30-32 weeks gestation with those of published data that adhered to the 2010 CDC revised guidelines for screening for GBS later in pregnancy.

Study design: Screening of 24,950 pregnant women for colonization with GBS at 30-32 weeks gestation was performed at our institution in this prospective study between 1995-2011. Chemoprophylaxis was administrated to GBS positive women and to those with risk factors for having infants with early-onset GBS disease. Neonatal outcomes were documented. Comparison was made both with a historical cohort of pregnant women who had been neither screened nor treated prophylactically and with published CDC data in which GBS screening had been preformed closer to term.

Results: In the study cohort, there were 63 infected infants (0,24%); 8 infants had had neonatal sepsis and one infant with sepsis expired. In the comparison, non-screened, non treated group, there were 149 infected infants (0,76%), 31 with neonatal sepsis, 29 of whom expired. .

Conclusion: Screening pregnant women for Group B Streptococcus carrier status 30-32 weeks gestation in a population with a high premature birth rate may help in preterm labor management but result in a higher incidence of early onset GBS neonatal disease when compared to published data that follow CDC guidelines.

Keywords: GBS neonatal infection, GBS screening at 30-32 weeks of gestation

 

Supplement

Until 1995, there had been no screening or prophylactic protocol at our institution. Factors we took into consideration in implementing a screening strategy that year included not only cost and feasibility but also Hungary’s high premature birth rate. An intermediate point, namely screening at 30-32 weeks was chosen as a result.

Our prospective study spanned 16 years. It was designed in order to first confirm the generally accepted benefit of instituting a GBS screening and a GBS chemoprophylaxis program at our institution where no such program previously existed. Secondly, it was designed to evaluate the effectiveness of screening at 30-32 weeks gestation by comparing our results with published CDC data that adhered to their guidelines for screening later in pregnancy, generally at 35-37 weeks gestation.

As a result of our findings, we will have to revisit and reconsider our protocol design. We may opt to keep the earlier screening schedule but just selectively apply it to those women who are at an increased risk for premature delivery. Known risk factors for premature delivery are a prior premature delivery, maternal age, multiple gestations, maternal chronic conditions, and poor prenatal care. We have come to realize that rescreening of these women at 35-37 weeks gestation will have to be performed if they proceeded to deliver closer to term. Women with no known premature delivery risk factors could follow the standard, recommended schedule.

In summary, vaginal Group B Streptococcal colonization is an important risk factor for neonatal infection that can largely be prevented by selective intra-partum chemoprophylaxis. From our study, we have arrived at some conclusions and recommendations that we ourselves and other institutions might consider. As far as prophylactic treatment, earlier treatment of colonized women and particularly those who are at increased risk of having severely infected newborns should be considered and somehow attempted so that they are able to complete the antibiotic regimen prior to delivery. The screening schedule chosen, we have come to realize, has to include testing pregnant women closer to term as the CDC/ACOG guidelines recommend. The high false negative rate that results from testing earlier ultimately leads to a higher incidence of early onset GBS disease because the group of women who converted to a positive carrier status later in pregnancy go largely untreated. We discovered that this is, indeed, a difficult trade off for us: one between having, on the one hand, earlier GBS results for the estimated 10% of women who go into premature labour in Hungary and having, on the other hand, an overall lower incidence rate of infected newborns with a protocol that largely ignores the needs of this group. We propose, therefore, that GBS screening at 30-32 weeks gestation could ,perhaps, be an additional not an alternative screening point that could be selectively applied only to those expectant mothers who have known risk factors for premature delivery. This assures a positive cost/ benefit ratio. To aid in screening and prevention, public health agencies in the future might considerer putting efforts aimed at the development of a rapid diagnostic test for GBS as well as the development a polyvalent GBS vaccine (25).

TABLE 1.   Prevalence of GBS infection earlier (1984-1994) and during the study period (1995-2011) within all neonatal infectionstab1

TABLE 2.  GBS neonatal infections related to maternal risk factors

tab2

HB

Dr. Boldizsar Horvath, MD PhD

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