max brinsmead phd franzcog july 2012 n.
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Max Brinsmead PhD FRANZCOG July 2012. GBS in Pregnancy To screen or not to screen?. Preamble. Group B Streptococcus is the most frequent cause of severe neonatal infection within 7 days of birth Incidence 0.5 – 1.5 per 1000 Risk of death is 10 – 30% And there is also morbidity in survivors

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GBS in Pregnancy To screen or not to screen?

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  • Group B Streptococcus is the most frequent cause of severe neonatal infection within 7 days of birth
  • Incidence 0.5 – 1.5 per 1000
  • Risk of death is 10 – 30%
      • And there is also morbidity in survivors
  • 15 – 30% of pregnant women are carriers of GBS (Varies with climate)
  • 50% of their infants will become colonised during birth and
  • 1 – 2 % will develop sepsis
  • Intrapartum antibiotics significantly reduces the rate of neonatal GBS sepsis
possible strategies
Possible strategies
  • Identify and treat high risk patients – no screening
      • UK (unchanged view in 2012)
  • Screen all and treat all GBS carriers
      • USA and many Australian hospitals
  • Screen all and treat only those with additional risk factors
      • Canada
Before embarking on a program of screening all pregnant women a number of questions need to be answered...
questions to be answered
Questions to be answered:
  • Will screening identify all those who need treatment?
  • Is treatment effective?
  • Is treatment safe?
  • Would another strategy be just as effective?
does screening identify all who need treatment
Does screening identify all who need treatment?
  • Must use selective culture medium
  • Best to use vaginal AND rectal swab
  • Best done at 35 – 37 weeks
      • High but not 100% correlation with carriage at term
  • And this does not detect those who labour before the swab result is available
  • And not required for all other risk groups:
    • Previous GBS-affected baby
    • Febrile in labour
    • Incidentally-detected GBS
does screening identify all at risk from gbs
Does screening identify all at risk from GBS?

But there’s more…

  • It is agreed that intrapartum antibiotics are effective only against early onset (EO) disease
  • Has no effect on the incidence of late onset GBS sepsis (>7 days of age)
  • The postpartum administration of antibiotics to the neonate is not an option
  • Rapid intrapartum testing or the antenatal detection of the high risk mother is the best option for the future
  • A role for immunisation?
is treatment effective
Is treatment effective?
  • There are no RCTs
  • Observational studies show that intrapartum antibiotics reduce the risk of neonatal GBS sepsis by 50 – 95%
    • Meta analysis by RCOG says 86%
    • But this could be due to effects of antibiotics on the diagnosis
    • No study has shown that Rx reduces overall rate of neonatal sepsis or death
  • Rate of GBS sepsis fell by 33 – 70% in the US after introduction of universal screening
    • But rate of neonatal deaths from GBS is the same in the UK
    • And rate of GBS sepsis in black US babies rose 70%
is treatment effective1
Is treatment effective?
  • Strictly speaking the answer is “unproven”
is the treatment safe
Is the treatment safe?
  • There are no RCTs
  • Some 15 – 30% of all women require treatment
  • You have to treat 714 women to prevent one case of neonatal sepsis
  • And 7000 women to prevent one neonatal death
  • Risk of fatal maternal anaphylaxis 1:100,000
  • This means one maternal death for every seven (7) babies saved
  • Unknown risks from non-fatal anaphylaxis
  • Unknown problems from antibiotic use
is the treatment safe1
Is the treatment safe?
  • So the answer is “maybe NOT”
disadvantages of universal screening
Disadvantages of universal screening
  • The medicalization of birth
  • Costs of screening and treatment
  • Potential effects of antibiotics on neonatal gut flora
    • Use penicillin not Ampicillin or Amoxil
  • Emergence of resistant organisms
other strategies
Other strategies?
  • Intrapartum rapid screening using PCR or optical immunoassay (OIA)
    • Second to universal treatment with antibiotics this is the most cost effective
  • Immunization against GBS
    • Looks promising
so why do i practise universal screening for gbs
So why do I practise universal screening for GBS?
  • A personal close call with GBS sepsis in 2003
    • We call this a case series of one!
  • US experience of a universal screening policy
      • Has significantly reduced the incidence of early-onset GBS infection
  • Peer pressure
    • Most large units in Australia now screening
    • Any affected patient who is not screened is very unhappy
  • It’s easier to remember and…
  • It’s very acceptable to women
case history page 1
Case History Page 1

Olivia G Age 28 G4P0

  • Black flashing eyes
  • Attending for 12m with recurrent miscarriage
      • Two in the first trimester
      • One in the second trimester
  • New partner
  • Spontaneous conception
  • Bleeding of unknown cause at 18 and 33w
  • Wedding at 36w
  • Admitted at 37w with “a few contractions”
case history page 2
Case History Page 2
  • Awake all night with fever, backache and sweats
  • Membranes intact
  • Temp 37.3 No uterine tenderness
  • CTG – Baseline 170 bpm & reduced STV
  • “Probably viraemia” but for FBC, HVS & UMCS
  • At 1200 hrs CTG improved & Olivia now afebrile
  • BUT WCC >25,0000 and 96% neutrophils
  • “A few gram pos cocci in the HVS”
  • Rx IV Ampicillin 1G at 12 midday
case history page 3
Case History Page 3
  • At 4 pm Olivia is in established labour
  • CTG – baseline 170 bpm and little STV
  • VE: 2 – 3 cm, effaced ARM Clear liqour
  • Rx IV Ampicillin 1G repeated
  • At 5 pm CTG and Cx unchanged
  • Making preparations for em CS but
    • theatre busy until 6 pm
    • anaesthetist meeting the mayor and
    • assistant on the beach with 30 teenagers
  • At 5:45 pm – Olivia wants to push!
case history page 4
Case History Page 4
  • Delivery assisted by ventouse and forceps
  • Big episiotomy and lotsa stitches HB 63 two days later
  • Gram stain of gastric aspirate “teeming with gram positive cocci”
  • Neonatal FBC showing classic signs of bacterial sepsis
  • Maternal HVS, urine, fetal gastric aspirate, body swabs and blood all grew GBS
  • Baby treated with IV antibiotics and did well
new engl j med july 2002
New Engl J Med July 2002:
  • A multicentre retrospective cohort study of 629,912 livebirths 1998 - 99
  • Selected 5144 births by random stratification
  • Risk of neonatal GBS sepsis was significantly lower in those hospitals where screening was practised compared to those where a risk-based approach was used (RR 0.46, 95% CI 0.36-0.60)
  • This difference could not be corrected by failure to treat for identified risk factors
2012 update 1
2012 Update 1
  • Immunisation remains elusive because of the number of subtypes
  • Rapid testing with PCR proves disappointing but direct plating onto culture medium at the bedside can hasten the detection
  • Professional women in Hong Kong had a significantly higher rate of colonisation than “housewives”
  • Someone has shown that it is more cost effective to simply treat any woman who has previously been GBS colonised rather than re screen and treat
  • Self collection of swabs is as good as professional collection
  • The doses of Clindamycin previously recommended are not sufficient
  • In a retrospective cohort study of 254 early-onset GBS sepsis in neonates in the US 61% were born to women who were screen negative
      • The others occurred in patients who had not been screened
2012 update 2
2012 Update 2

The US CDC has reviewed its guidelines, endorsed universal screening and made some further modifications…

  • RCT’s of vaginal chlorhexidine disappointing
  • Only 4 cases of non fatal anaphylaxis reported in the US since universal screening and treatment recommended in 1996
      • 1 – 4 % of patients will have maculopapular rash
  • Penicillin-resistant GBS seen in Japan and ↑MIC noted elsewhere
      • 32% GBS resistant to Erythromycin and
      • 20% resistant to Clindamycin (same group)
      • Use Cephalosporin and Vancomycin
  • Urine colony count >105 significant (screening not required)
  • Women scheduled for elective CS should be screened at 35 – 37 weeks in case they have PROM
  • Revised doses of Penicillin and Clindamycin
  • Revised alogorithm for observation of GBS-exposed and intrapartum-treated babies (secondary prevention)