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GBS can be present at any time - in a woman's first pregnancy, or in subsequent pregnancies. It can be a threat during pregnancy, around delivery and afterwards. There are five recognised situations which increase the chance that a baby will be exposed to GBS, if susceptible, of developing GBS infection. Each of the risk factors shown panel below increases the risk of GBS infection in a newborn baby:
- Mothers who have previously had a baby infected with GBS – risk is increased 10 fold
- Mothers who have been shown to carry GBS in this pregnancy or GBS has been found in the urine at any time during this pregnancy – risk is increased 4 fold
Any of the following clinical risk factors – risk of GBS infection is increased 3 fold for each
- Labour starts or membranes rupture before 37 weeks of pregnancy is completed (i.e. preterm).
- Where there is prolonged rupture of the membranes – more than 18 hours before delivery.
- Where the mother has a raised temperature* during labour of 37.8°C or higher.
*If a woman has an epidural, a slightly raised temperature may be of less significance than in a woman with no epidural.
Carrying GBS, combined with one or more clinical risk factor, increases the risk at least 12 times.
75% of early-onset GBS disease and 90% of resultant deaths follow deliveries with one or more of these risk factors.
About half of the babies born to mothers colonised with GBS at the time of delivery will become colonised themselves and, of these, only around 1 in 200 will develop GBS disease, even without any preventative medicine during labour. Carrying GBS during labour and delivery does not mean necessarily that you or your baby will become ill.
Simply carrying GBS previously, without a positive test result during the current pregnancy, does not mean a woman should be offered intravenous antibiotics in labour unless one or more other risk factors are also present. |
