How many people carry GBS?
GBS is a normal bacterium which is carried by up to 30% of adults, most commonly in the gut, but for up to 25% of women, in the vagina too.
Not everyone carries GBS and pregnancy does not 'bring it on' or cause a 'flare-up' of group B Strep. It can be passed from mother to baby during labour and, although this causes no problems for most babies, for a small number it can be deadly, causing blood poisoning, pneumonia and meningitis.
How can people become carriers of GBS?
GBS may be passed from one person to another through skin to skin contact, for example, hand contact, kissing, close physical contact, etc. As GBS is often found in the vagina and rectum of colonised women, it is commonly passed through sexual contact.
There are no known harmful effects of carriage itself and, since the GBS bacteria do not cause genital symptoms or discomfort, GBS carriage is not a sexually transmitted disease, nor is GBS carriage a sign of ill health or poor hygiene.
No-one should ever feel guilty or dirty for carrying GBS – it’s normal.
What are the chances of my baby developing a GBS infection?
The following are estimates of the chances a baby in Britain will become infected with GBS if no preventative measures are taken and no other risk factors are present:
- 1 in 1,000* where the woman is not known to be a carrier of GBS;
- 1 in 400 where the woman is carrying GBS during the pregnancy;
- 1 in 300 where the woman is carrying GBS at delivery; and
- 1 in 100 where the woman has had a previous baby infected with GBS.
*This is a broadly accepted estimate of the number of GBS infections in newborn babies that would occur if no preventative intravenous antibiotics in labour are given and this estimate has been used throughout this document. Recent UK research suggested this may be a serious underestimate of the incidence of GBS infection in newborns, which could be as high as 3.6 per 1,000.
If a woman who carries GBS is given antibiotics during labour through delivery in accordance with our medical advisory panel’s recommendations at Prevention, the baby’s risk is reduced significantly.
- 1 in 8,000 where the mother carries GBS during pregnancy;
- 1 in 6,000 where the mother carries GBS at delivery; and
- 1 in 2,200 where the mother has previously had a baby infected with GBS.
The vast majority of pregnancies can be managed so that babies are protected and born free of GBS infection.
Should I take antibiotics before I get pregnant to get rid of the GBS?
No antibiotics tested so far seem able to do this reliably. Antibiotics may temporarily eradicate vaginal colonisation with GBS, but colonisation in the intestines will remain and recolonisation of the vagina will occur.
I have vaginal symptoms - are these caused by GBS?
A GBS positive result from a vaginal swab means the woman’s vagina was colonised with GBS when the swab was taken. GBS carriage is asymptomatic – it is not associated with symptoms. Just because GBS is isolated from a swab taken to investigate vaginal symptoms does not mean GBS is the cause of those symptoms. We know of no publication that convincingly correlates GBS carriage with any vaginal symptom, and people have specifically looked into this.
Antibiotics for GBS carriage are not indicated. No antibiotics tested so far have been shown to eradicate GBS reliably from the body so, even if antibiotics clear the GBS colonisation of the vagina (and they may not), recolonisation from the intestines will occur. The time when antibiotics have been proven to be effective against GBS infections in babies is when they are given intravenously to the mother once her waters have broken or as soon as labour has started and at intervals until delivery.
I carry GBS in my vagina. Does my partner need to be tested?
No. Colonisation with GBS is normal and does not need treatment. A third of the adult population carries GBS, without symptoms – you don’t need to be tested for it, nor do you (or he) need antibiotics for it. GBS is not a sexually transmitted disease. Carrying GBS is not a disease at all!
Will antibiotics get rid of GBS colonisation from my vagina during pregnancy?
Antibiotics won’t necessarily get rid of colonisation in the vagina and, even when they do, they will do so only temporarily - recolonisation will occur. Evidence shows taking antibiotics before labour does not reliably eradicate GBS carriage - and there’s no evidence that it reduces the incidence of GBS infection in newborn babies either. Studies have shown no substantial difference in GBS carriage at delivery between women treated with antibiotics during pregnancy and those not treated. In one study, nearly 70% of colonised women treated with antibiotics for 12 to 14 days during the third trimester (28 to 40 weeks of pregnancy) were colonised three weeks later and again at delivery.
Antibiotics during pregnancy for GBS carriage are not indicated. GBS cultured from a vaginal swab show the vagina is colonised with GBS, not infected. No antibiotics tested so far have been shown to eradicate GBS reliably from the body so, even if antibiotics clear the GBS colonisation of the vagina (and they may not), recolonisation from the intestines will occur. Evidence shows taking antibiotics neither gets rid of GBS carriage nor reduces the incidence of GBS infection in newborn babies. Antibiotics have been proven to be highly effective at stopping GBS infections in newborn babies when given intravenously to the pregnant woman as soon as her membranes have ruptured or labour has started.
Do I need antibiotics if GBS is found in my urine?
Yes, though remember to tell your health professionals if you have ever had an allergic reaction to penicillin or any other antibiotic. Urine is supposed to be sterile so, if GBS is found in your urine, you should be treated with oral antibiotics when diagnosed and this treatment repeated until urine tests come back clear. A 5-day course would be appropriate and it’s important the urine is retested 7-10 days after finishing the antibiotics.
Treatment for a GBS positive urine sample, whether you have symptoms of a urine infection or not, is essential during pregnancy since, if left untreated, such infections can cause kidney damage and have been linked to preterm labour.
GBS having been found in the urine during pregnancy means you should also be offered intravenous antibiotics once labour has started.
Should I be tested regularly for GBS?
No. If you have had a positive test result for GBS at any time during your current pregnancy, you should be offered intravenous antibiotics from the start of your labour, until delivery.
The conventional test available on the NHS is unreliable – it misses up to 50% of GBS carriers. There is a reliable test but this is not available from most NHS hospitals, although it is available from two private laboratories which offer a postal service. See Which Test for GBS carriage? by clicking here.
And if you get another positive result from the conventional test, all it tells you is that you are still carrying GBS. If it gives you a negative result, all it tells you is you may not be still carrying GBS (but remember the negative test results aren’t very reliable). Neither of these results should make any difference to your being offered intravenous antibiotics in labour.
Are the tests for GBS colonisation reliable?
The conventional tests available are not very reliable when they give a negative result – they give a falsely negative result up to 50% of the time when they should be positive! On the other hand, if you get a positive conventional test result, that is very reliable. See Which Test for GBS carriage? by clicking here.
Any positive result (conventional, ECM or PCR) means you should be offered intravenous antibiotics as soon as possible after the start of your labour or membrane rupture to protect your baby from GBS infection.
[GBSS fully endorses the availability of reliable antenatal GBS testing but has no links to nor receives any money from any laboratory. Indeed we hope many laboratories will offer the ECM test and, as they do, we'll provide details of their service.]
I carried GBS in my last pregnancy - my baby was fine. Do I need IV antibiotics this time?
GBS can quite naturally come and go from the vagina so the bacteria can be there one month and not the next ... and back again at some other time (though research has shown that, using sensitive tests, the results are highly predictive of colonisation status for around five weeks). There is currently no good data that can predict carriage of GBS over periods of a year or more. However, since there may be some increased chance of a woman carrying GBS in a pregnancy if GBS has been isolated previously, it is the view of our medical panel that, if possible the pregnant woman should be offered a reliable (ECM or PCR) test at 35-37 weeks of pregnancy to establish whether she is still carrying GBS. If the test is positive, then she should be offered intravenous antibiotics as soon as possible once labour has started.
If a reliable ECM or PCR test result is not available and labour starts after 37 weeks of pregnancy, then the view of our medical panel is that previous carriage status should be treated as an additional risk factor (increasing the risk of a baby developing GBS infection where preventative antibiotics in labour are not given from an estimated 1 in 1,000 in the general population, to approximately 1 in 500 for a woman whose current GBS status is unknown, but where GBS was isolated before the current pregnancy). Our medical panel's view is that the 'previous carrier' risk factor alone is insufficient to recommend offering intravenous antibiotics in labour against GBS infection in the baby, unless another clinical risk factor was also present.
What happens if I get a negative ECM or PCR test result?
A woman who has a negative ECM (enriched culture medium) or PCR (polymerase chain reaction) test result at 35 plus weeks of pregnancy does NOT need to be offered intravenous antibiotics in labour to prevent GBS infection in her baby (but antibiotics may be indicated for other reasons) . Research shows that, if performed within 5 weeks of delivery, an ECM test giving a negative result is 96% predictive of GBS not being carried at delivery (4% of women acquired carriage between testing and delivery) so the risk of acquiring carriage between doing the test and giving birth is very small.
If a woman has not had an ECM or PCR test result OR the less reliable conventional test has been negative during the pregnancy, she should be offered intravenous antibiotics from the onset of labour if one or more risk factors listed at Who is at risk? is present.
A woman who has previously had a baby who developed GBS infection should ALWAYS be offered intravenous antibiotics in subsequent pregnancies, from the onset of labour or membrane rupture until delivery, regardless of any test results.
And a woman who has had any positive test result (from the urine, vagina or rectum) during the current pregnancy should also be offered intravenous antibiotics from the onset of her labour or membrane rupture until delivery.
I had a positive result early in my pregnancy. Should I be tested again?
If you have had a positive GBS test result (from the vagina or rectum) during the current pregnancy, and no further tests, you should be offered intravenous antibiotics from the onset of labour or membrane rupture until delivery (antibiotics are recommended if the positive result was from the urine).
However, if the positive result was early in your pregnancy, you may have lost carriage by the time your baby is born. If you want to find out whether you are still carrying GBS, you can have a sensitive test at 35-37 weeks. If the sensitive test result is negative, then intravenous antibiotics are probably not indicated, since research shows that a sensitive test giving a negative result within 5 weeks of delivery is highly predictive of the mum not carrying GBS at delivery. The risk of acquiring carriage between doing the test and giving birth is very small.
Must I have intravenous antibiotics if I’ve had a positive result during this pregnancy?
If you have had any positive GBS test result from the vagina or rectum during the current pregnancy, you should be offered intravenous antibiotics from the onset of labour or membrane rupture until delivery. However, you may choose not to have them if there are no additional risk factors - only a small percentage of babies born to colonised mothers will develop GBS infection. However, if you decide against antibiotics, it would be prudent for the baby to be observed by trained staff for at least 24 hours (and ideally for 48 hours). If the positive test was from the urine, this means that the GBS was more invasive, and so antibiotics will be recommended even if a vaginal swab is subsequently negative.
I’m at risk of premature labour; should I take long-term antibiotics?
Along with many other bacteria found in the vagina, GBS can cause infection of the baby in the womb, which can result in preterm birth, stillbirth and late miscarriage. However, these are usually caused by a variety of factors other than GBS: genetic defects, gynaecological problems, other infections, etc. If a woman has had any of these problems in the past, she should make sure these possibilities are investigated fully by a consultant obstetrician at booking (or before) regardless of whether or not she is colonised with GBS. Such complications are uncommon and GBS is a rare cause of them.
For the antibiotics tested so far, their use throughout pregnancy does not prevent preterm delivery due to any cause, including GBS. Also, the effects of long-term antibiotics on the baby during pregnancy have not been assessed; although we know that short courses of, for example, amoxycillin, seem to be exceptionally safe.
I’m worried I won’t get 4+ hours of IV antibiotics before my baby is born.
A very small study1 showed giving intramuscular penicillin eradicated GBS colonisation for at least 6 weeks in 75% of women known to carry GBS. So far, this very small study (50 of 78 women received intramuscular antibiotics) has not been repeated, so it is difficult to give advice based upon this data.
For women known to carry GBS where it is not expected that the intravenous antibiotics can be given for at least 4 hours before delivery, an intramuscular injection of 4.8 MU (2.9 g) of Penicillin G at about 35 weeks of pregnancy may be useful in addition to intravenous antibiotics given from the onset of labour or membranes rupturing until delivery to try to eradicate GBS colonisation until after delivery.
Regardless of whether you have intramuscular antibiotics to try to eradicate GBS colonisation, it is recommended that all women in higher risk categories be offered intravenous antibiotics from the onset of labour or waters breaking, plus at 4 hourly intervals until delivery.
There are downsides of intramuscular penicillin - the injection is painful, there is a small risk of an allergic reaction and of antibiotic resistance developing (see below). These risks are repeated with the intravenous antibiotics given in labour.
For intramuscular antibiotics, there are no known alternatives to penicillin for penicillin-allergic women.
1(Bland ML, Vermillion ST, Soper DE. Late third-trimester treatment of rectovaginal group B streptococci with benzathine penicillin G. Am J Obstet Gynecol 2000 Aug;183(2):372-6)
Should I be induced, with the IV antibiotics starting as I’m induced?
Our medical advisers do not recommend induction for anyone as a way of combating GBS infection in babies. Carrying, or being at risk of, GBS is not a reason to be induced.
If you live a long way from the hospital or have a history of very fast labours, then induction is one way to try and ensure you get sufficient intravenous antibiotics in labour. However, induction is not without risk itself, especially before the due date. You should discuss the potential risks and benefits of an induction with your obstetrician, because they will vary dependent upon your personal circumstances.
If you need to be induced for obstetric or medical reasons, the recommended intravenous antibiotics should be started as soon as possible once labour has started or waters have broken (naturally or artificially), whichever happens first and should be repeated 4-hourly until delivery, and ideally for at least 4 hours before delivery.
What are the potential risks of antibiotics? Taking antibiotics should not be done lightly – they can have side effects that need to be considered in relation to the potential benefits and it is important that you tell your health professionals if you have ever had an allergic reaction to penicillin or any other antibiotic.
Although good data is hard to find on this subject, the generally quoted estimated risks for penicillin are:
- 1 in 10 of the mother developing a mild allergic reaction, such as a rash;
- 1 in 10,000 of the mother developing a severe allergic reaction (anaphylaxis); and
- 1 in 100,000* of the mother developing fatal anaphylaxis, resulting in her death.
And severe complications can occur in the unborn baby even when the anaphylaxis developed by the mother is not life threatening, although this risk is probably overstated.
Although often quoted, these figures are generally accepted as being a significant over-estimate of the risk - a recent paper stated that, in the US between 1997 (the year after the CDC recommended intravenous antibiotics in labour for women whose babies were at higher risk of developing GBS infection) and 2001, an estimated 1.8 million women were given penicillin in labour and no deaths occurred, so an estimate of a 1 in 100,000 risk of death from penicillin anaphylaxis is likely to be an over-estimate. The prevention of neonatal group B streptococcal disease. MR Law, G Palomaki, Z Alfirevic, R Gilbert, P Heath, C McCartney, T Reid, S Schrag on behalf of the Medical Screening Society Working Group on GBS Disease. J Med Screen 2005;12:60-68.
Whenever antibiotics are taken, there are always risks of antibiotic resistance developing. When antibiotics are given to pregnant women, this could affect the mother and her baby. When antibiotics are given around birth and in the early weeks of life, there is the chance they may increase the likelihood of the baby developing allergies. Although a lot of press space is given to this, unfortunately data are lacking on whether it’s the giving of antibiotics that causes the allergies, or whether there are other reasons (for example, genetics, environment, disease, etc.). This is yet another area where more research is needed!
Bearing all this in mind, you need to weigh up whether you consider the risks are acceptable in comparison with the potential benefits and, if so, in what circumstances you would want to be offered antibiotics.
What are the signs that GBS is affecting my unborn baby?
If your pregnancy is progressing normally, then there is no reason to suspect GBS is infecting your baby. If a GBS infection is present, you’ll usually go into labour or your membranes will rupture. And that’s the time to get to hospital as quickly as you can to receive the intravenous antibiotics to give your baby the best protection possible.
Will a Caesarean prevent GBS infecting my baby?
Caesarean sections do not eliminate the risk of GBS to a baby of developing GBS infection since the bacteria can cross intact amniotic membranes to set up an infection in the baby, although they do reduce the risk.
However, Caesareans are not recommended as a method of preventing GBS infection in babies: they do not eliminate the risk; there are significant risks associated with a Caesarean section; and the recommended intravenous antibiotics during labour are both low risk and highly effective.
Are membrane sweeps safe for women who carry GBS?
Using a gloved finger passed through the cervix (neck of the womb) to separate the baby’s membranes from the lower part of the uterus is known as a ‘membrane sweep’. In women who are at or beyond the due date, it encourages spontaneous labour and can enable about 10% of women to avoid an artificial induction of labour.
There is currently no good evidence that membrane sweeps are harmful in women known to carry GBS. Indeed the results of trials of membrane sweeps don’t show any increase in problems caused by GBS in women having sweeps, and it is highly likely these trials would have included many women carrying GBS at the time.
However, there remains a theoretical risk that a membrane sweep might occasionally introduce GBS into the uterus, and so our medical advisory panel advises caution in using a membrane sweep for women known to carry GBS when there are other acceptable alternatives (for example, induction of labour with prostaglandin gel introduced into the vagina).
I want a water birth
There are no known contra-indications for a woman known to carry GBS having a water birth. As for all women carrying GBS during the current pregnancy, our medical advisory panel recommends they should be offered intravenous antibiotics from the onset of labour until delivery. It is not a good idea to get the cannula (which delivers the intravenous antibiotics to the mother) wet, but this can be managed - specially designed waterproof dressings are available which keep the site sterile and dry whilst still enabling the health professional to monitor the site visually. You can read an article about waterbirths by clicking here.
I want a home birth
Our medical advisory panel's recommendations for stopping GBS infections in newborn babies are the same for home births as for hospital births - women whose babies are at higher risk of developing GBS infection should be offered intravenous antibiotics from the start of labour until delivery.
Home births are becoming increasingly popular and, if you want a home birth with intravenous antibiotics during labour until delivery, it may be possible for your midwife to give you intravenous antibiotics prescribed for you by your GP. This is not widely available. Some areas won't permit intravenous antibiotics to be given at home - there is a small risk that you would get a severe allergic reaction to the antibiotics (see What are the potential risks of antibiotics? above) and, obviously, there is no intensive care unit nearby. The risk is small but your health professionals may be anxious. Of course, around 25% of women having home births probably carry GBS in their vagina at delivery without knowing it. This issue needs to be discussed with your medical team.
Oral antibiotics are not recommended for women for GBS carriage during pregnancy or labour – quite simply, there’s no evidence that they prevent GBS infections in babies. If you have set your heart on a home birth, you may wish to consider having intramuscular antibiotics as outlined in I'm worried I won't get 4+ hours of IV antibiotics before my baby is born above, though our medical advisory panel do not recommend them in lieu of intravenous antibiotics during labour, but they may be better than nothing if that really is the only alternative.
I want to breastfeed my baby
Our medical advisory panel strongly recommends you should be encouraged to breastfeed your baby. Although there have been isolated cases describing GBS infection possibly related to breast milk contamination, the advantages of breast feeding will, in our medical advisory panel's opinion, greatly outweigh the remote risk of transmitting GBS via breast feeding. High hygiene standards need to be maintained for all breastfeeding mothers, with the hands and nipple areas being kept clean.
The intravenous antibiotics recommended above (see Prevention here ) for pregnant women during labour through to delivery to protect her unborn baby from GBS infection are safe for breastfeeding mothers, although you should make sure your medical professionals know you intend to breastfeed your baby.
If you develop mastitis or a breast abscess, you should seek medical advice regarding breast-feeding.
GBS and Swine Flu
GBS is not a factor in the decision whether to Mum should be vaccinated against swine flu, regardless of whether she knows she carries GBS or not. |
