8A) Antenatal Care: Group B Streptococcus

Question 1

Type of organism Group B Streptococcus (6 facts)

Answer 1

• Gram positive coccus bacteria
• Forms chains
• Catalase negative
• Facultative anaerobe
• Lancefield group B
• Beta-haemolytic

Question 2

Real name Group B Streptococcus

Answer 2

Streptococcus agalactiae

Question 3

Incidence of GBS carriage at delivery (overall, with previous colonisation, if test at 36 weeks positive, if test at 36 weeks negative)

Answer 3

Overall carriage rate: 20-40%
Previous GBS colonisation: 50%
+ve test at 36/40: 75%
-ve test at 36/40: 5%

Question 4

Ethnicity with highest and lowest GBS carriage

Answer 4

Highest: Black African
Lowest: SE Asian

Question 5

Risk factors for developing early-onset GBS disease (EOGBS)

Answer 5

• Previous EOGBS
• Known GBS colonisation
• Preterm labour
• PROM
• Pyrexia in labour
• Suspected maternal infection

Question 6

Incidence of EOGBS (overall, with previous colonisation, if test at 36 weeks positive, if test at 36 weeks negative, if colonisation known and IAP given, preterm labour, pyrexia in labour)

Answer 6

Overall risk: 1 in 1750
Previous GBS colonisation: 1 in 800
\+ve test at 36/40: 1 in 400
\+ve test and receive IAP: 1 in 4000
-ve test at 36/40: 1 in 5000
Preterm labour: 2 in 1000
Pyrexia in labour: 5 in 1000

Question 7

Mortality and disability associated with EOGBS

Answer 7

7.5% disability

5% mortality

Question 8

Intrapartum antibiotic prophylaxis regime

Answer 8

• 3 gram benzylpenicillin loading dose and then 1.5gram 4 hourly until delivery

Penicillin allergy:

• 1.5 gram cefuroxime loading dose and then 750mg TDS
• Vancomycin 1 gram BD

Question 9

Management of patient with GBS colonisation in previous pregnancy

Answer 9

Offer either testing at 35-37 weeks or IAP.

Question 10

Management of patient with GBS disease in previous pregnancy

Answer 10

Offer IAP

Question 11

Management of patient with GBS on urine sample in this pregnancy

Answer 11

Treat UTI and offer IAP

Question 12

Management of patient with GBS on vaginal/rectal swab in this pregnancy

Answer 12

Offer IAP

Question 13

Management of patient with rupture of membranes:

• Term and known GBS
• Term and GBS status unknown/negative
• Preterm and known GBS
• Preterm and GBS status unknown/negative

Answer 13

• Term and known GBS: Offer immediate augmentation and IAP.
• Term and GBS status unknown/negative: Offer augmentation after 24 hours.
• Preterm and known GBS: Erythromycin, offer augmentation and IAP from 34/40.
• Preterm and GBS status unknown/negative: Erytromycin and IAP once in labour

Question 14

Management of pyrexia in labour

Answer 14

Broad spectrum antibiotics e.g. amoxicillin 2 gram QDS or cefuroxime 1.5gram QDS

Question 15

Management of baby at risk of EOGBS

Answer 15

• Term + IAP: No special considerations
• Risk of EOGS and no IAP: Obs 1 hourly until 2 hours and then 2 hourly until 12 hours
• Clinical signs of EOGBS: Penicillin + gentamicin within 1 hour
• Previous EOGBS: Obs 1 hourly until 2 hours and then 2 hourly until 12 hours.

Question 16

Mortality associated with EOGBS in PTB

Answer 16

Increased to 20-30% in PTB