Group B Strep

Question 1

What proportion of women are carriers?

Answer 1

10-30%

Question 2

What are the 2 types of neonatal GBS infection?

Answer 2

early onset EOGBS

• within first week
• pneumonia and respiratory compromise

Late onset GBS

• at 1 week -3 months old
• meningitis and disseminated sepsis

Question 3

What is the aim of GBS prophylaxis?

Answer 3

To prevent EOGBS in at risk women.

It has no effect on incidence of late onset GBS.

Question 4

What screening is recommended by RANZCOG for GBS?

Answer 4

• Identifying women with risk factors based on their obstetric history (e.g. previous baby EOGBS, current preterm labour etc)
• Rectovaginal swabs taken at 35-37 weeks (must use enriched culture medium)
• Any MSU in pregnancy with GBS warrants prophylaxis in labour

Question 5

What are the risk factors for EOGBS?

Answer 5

• Previous baby with EOGBS or late onset GBS
• Known GBS carriage on swab
• GBS in urine at any stage antenatally
• Preterm labour <37 weeks
• Prolonged rupture of membranes
• Maternal fever ≥38
• clinical chorioamnionitis

Question 6

What are the potential options for EOGBS prevention?

Answer 6

• Screening
• intrapartum IV antibiotic prophylaxis
• GBS vaccine (currently in trials)

Question 7

Why is EOGBS such a concern?

Answer 7

• GBS is leading cause of neonatal sepsis.
• EOGBS affects 0.4-4/1000 live births
• EOGBS has 14% mortality rate (increased to 20% in preterm infants)

Question 8

What proportion of EOGBS can be prevented with intrapartum prophylaxis?

Answer 8

80%

Question 9

What are the possible choices of intrapartum prophylaxis?

Answer 9

IV benzyl penicillin 1.2g loading and 600mg Q4H (ideally started >4 hours prior to birth)

Alternatives:
Cefazolin
Clindamycin
Vancomycin

Question 10

What are the possible choices of intrapartum prophylaxis?

Answer 10

IV benzyl penicillin 1.2g loading and 600mg Q4H (ideally started >4 hours prior to birth)

Alternatives:
Cefazolin
Clindamycin
Vancomycin

Question 11

What is the importance of detailing on recto-vaginal swabs that you are screening for GBS?

Answer 11

They can use enriched culture medium.
This increases sensitivity from 50->90%.

If the mother is penicillin allergic it is worth asking for sensitivity to use most appropriate second line agent.

Question 12

Why screen at 35-37 week?

Answer 12

GBS colonisation fluctuates over time - if swabbed earlier in pregnancy may not detect GBS colonisation near timing of delivery.

GBS prophylaxis given antenatally is not effective - GBS recurrence occurs in 2/3 of cases.

Question 13

With regards to threatened preterm labour - how should EOGBS prevention be optimised?

Answer 13

• Take recto-vaginal swabs for GBS screening during assessment
• If in suspected preterm labour start intrapartum IV abs prophylaxis
• If labour stops prophylaxis can be withheld
• Swab can be used to guide prophylaxis if proceeds to labour within subsequent days

Question 14

How does known GBS carriage affect timing of IOL for PROM and PPROM?

Answer 14

• PROM at term - start IOL and GBS prophylaxis
• PPROM <34 weeks- usual oral erythromycin to prolong pregnancy, and IOL and GBS prophylaxis at 34 weeks, rather than expectant Rx till 37 weeks
• PPROM >34 weeks - IOL and GBS prophylaxis