Group B strep
Recently Queensland Health changed its policy on the dose of antibiotics given to women in labour. These changes affect women who have identified risk factors including Group B Strep and preterm labour. Women who are found to have a high temperature in labour and labouring women whose waters have been broken for 18 hours or more will also be affected by this change. However little information is provided to pregnant women regarding the evidence around intravenous antibiotics (IVAB’s – antibiotics directly into your vein) in labour, particularly when it comes to GBS. A consumer information leaflet produced by Queensland Health can be found here. While this is a good source of balanced information it doesn’t give you information about the changes Queensland has made to the recommended dosage given to women who consent to this treatment.
Here’s what you need to know to make an informed decision about whether you consent to IVAB’s in labour if you have been found to be GBS positive.
What is Group B Strep (GBS)?
Group B streptococcus is a variety of bacteria which are primarily found in the gut, vagina and urethra. It is found in people of all ages and sexes worldwide and is usually asymptomatic (you don’t even know you have it). It is not a sexually transmitted infection, however, people can become colonised with GBS through sexual contact. GBS bacteria are part of the normal microbiome in up to a third of people and colonise the vagina of about 25% of women. The life cycle of the GBS bacteria is said to be 4-6 weeks. This means that women who are colonised with GBS can still test negative from time to time.
GBS and your baby
Half of babies born to women with GBS also become colonised with the bacteria. The most common means of infection is through contact with GBS from the mother’s vagina, however, it can be passed on through contact with the mother’s skin and through the breastmilk. For 98-99% of babies, this presents no problem. The bacteria becomes part of their normal microbiome. However, 1-2% of babies will develop a GBS INFECTION rather than a GBS COLONY. While infection rates in newborn babies are very low, GBS is responsible for the majority of these cases. A GBS infection can have serious consequences for your baby and is considered to have a high mortality rate (10%). Babies with severe infection can also be left with long term consequences.
What are the odds?
If we pull the numbers together and apply them to a specific number of women these are the odds.
In a hospital birthing 5000 women per year:
- 25% with be GBS positive = 1250 women per year
- 50% of those babies will be colonised with GBS = 625 babies per year
- 1-2% of those babies will develop GBS infection = 6.25-12.5 babies year
- 10% of those babies will die = 0.625 – 1.25 babies per year (1 baby in a 7.5-15 month period.)
In real terms, this means if we knew the GBS status of every woman birthing in that facility and didn’t treat any of them we would lose one baby a year to GBS infection. While these seem like long odds (1:5000), potentially losing one baby a year to an infection which may be prevented by antibiotics in labour is unthinkable.
Do IVAB’s work?
Many studies have found that the incidence of GBS infection in the first seven days of life of newborn babies is greatly reduced if the mother has had IVAB’s in labour. While much of the research done around GBS and IVAB’s is not considered gold standard or high level, medical research cannot ethically perform the required trials to provide this evidence. Having found that IVAB’s reduce the incidence of GBS disease in newborns we cannot withhold treatment for babies with increased risk.
This is why women who are known to have risk factors for GBS in labour are advised to have antibiotics. However, babies can still develop GBS in the first 7 days (AKA Early-onset GBS disease – EOGBSD) when a GBS positive mother has IVAB’s in labour. Babies can also develop EOGBSD when their mother has tested GBS negative.
GBS infection risk factors
- A baby born before 37 weeks of pregnancy has increased risk of a GBS infection than a baby born at term.
- You have had a previous baby who was infected with GBS
- You develop a high temperature (> 38 degrees C) in labour or within 24 hours of your baby being born
- Your waters break more than 18 hours before your baby is born
- A GBS screen during this pregnancy has come back positive.
Group B strep screening
There are two ways that GBS is screened. How and when these tests are performed may change depending on your maternity care provider.
- A urine test may be done in early pregnancy with your blood tests. This may involve a test for bacteria, including GBS. It may also be done at any time during the pregnancy if you develop a urinary tract infection.
- A vaginal (or vaginal/rectal) swab which is either specific for GBS, or any bacterial infection.
A GBS positive result in any of these tests will prompt the recommendation for IVAB’s in labour.
Some health services perform universal screening by vaginal swab between 35-37 weeks of pregnancy. Others screen if and when they are given a reason to do so. Research around universal vs risk-based screening shows a negligible difference in outcomes with a lower cost for testing to the health service overall. Queensland Health has adopted the risk-based approach. However, should you wish to be screened for GBS you can request this from your health care provider.
Whatever method of screening is used, balanced information should be provided to you prior to you consenting to have the test performed. This is for a number of reasons:
- The testing can be uncomfortable and invasive (especially a vaginal or vaginal/rectal swab – these can be performed yourself at your appointment to minimise discomfort).
- If a positive result is returned you need to be aware of the recommended management of the associated risk. IVAB’s are also invasive and the treatment itself is not free of risk.
When considering consenting for (or requesting) this test to be performed, you need to know what you are going to do with the results. There is no point being tested if you would decline treatment for yourself and/or your baby. Additionally, if you are found to be group B strep positive and you decline treatment you will find that a number of health professionals will discuss your decision not to treat and you may feel pressured into complying. In Queensland, the babies of women who are not tested for GBS are treated no differently to babies of mothers who are tested and GBS negative.
Effective treatment of group B strep
If you consent to IVAB’s in labour we need to treat you to a level that the antibiotic gets to do its job. The antibiotics needed to prevent GBS disease depend on the drug being in the babies system for a certain length of time. Research has found that the level of antibiotic in your babies blood is at its highest 1 hour after being given. This is because it needs to make its way from your blood, across the placenta and into the baby. Once it’s there it needs to stay high enough to prevent the bacteria from taking hold.
To ensure we are keeping the antibiotic level in baby’s blood high enough, you will be given a high dose to start with followed by top-up doses every 2-4 hours (depending on your health service). These antibiotics are most effective with a minimum of 90 minutes to work. However, any antibiotics are sometimes better than none. Penicillin is the preferred antibiotic for GBS prevention. For women with a penicillin allergy alternatives are available. Low levels of antibiotic resistance have been found in some strains of GBS bacteria. All of these factors have contributed to Queensland Health increasing the recommended dosage. The IVAB protocol for the initial dose has changed from 1.2g to 3g. Top-up doses have increased from 600mg to 1.8 g.
Benefits and risks of IVAB’s
- Reduces the risk of GBS infection in the newborn baby from birth to 7 days of age
- Reduces risk of GBS related infection in the unwell mother
- Anaphylaxis (allergic reaction to antibiotic) in mother
- Less severe reactions including rash
- Thrush (mother and baby)
- Negative affect on the good bacteria in the system of mother and baby (the Microbiome)
Ok. So you have been found to have risk factors for a GBS infection and consented to antibiotics in labour. How do you support yours and your babies microbiome? There is good news! Some research suggests that lactobacillus bacteria (such as you find in probiotics) can resist penicillin when under stressed conditions (such as during labour). If you have risk factors prompting IVAB’s in labour it may be a good idea to start taking probiotics prior to labour so the good bacteria have a chance to make themselves at home.
Probiotics after your baby is born will help to balance out your gut flora again. Minimise your refined sugar intake after the baby is born, as the microbes responsible for thrush thrive on it. Starve them and the good bacteria in the probiotics will be able to control them again. Breastfeed your baby whenever possible. Colostrum and breast milk are full of good bacteria that are there to colonise your baby’s gut. Your milk is probiotics for baby.
Dr Janelle McAlpine (PhD)
Queensland Clinical Guidelines, Queensland Health.
Antibiotic sensitivity of acid stressed probiotic lactobacillus acidophilus NCDC 291. N.K. Natt · S. Garcha. Jan 2011 · Internet Journal of Microbiology. Photo by Jjustas, used under licence from Shutterstock.com