Group B streptococcus
Group B streptococcus is an ordinary bacterium that lives in the bowel and the genital tract of roughly one adult woman in five and does her no harm at all.
On this page
Medicines commonly prescribed for Group B streptococcus
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: ORAL SOLUTION/SUSPENSION, 1000 mgActive substance: amoxicillinManufacturer: Laboratorios Normon S.A.Prescription requiredDosage form: INJECTABLE, -Active substance: amoxicillinManufacturer: Ldp Laboratorios Torlan S.A.Prescription requiredDosage form: Dispersible tablet, 1,1480 gActive substance: amoxicillinManufacturer: Sandoz Farmaceutica S.A.Prescription required
Group B streptococcus is an ordinary bacterium that lives in the bowel and the genital tract of roughly one adult woman in five and does her no harm at all. Carrying it is not an illness, says nothing about hygiene and is not something passed on through sex. Its whole significance falls into a few hours — the hours of labour, when the bacterium can reach a baby whose immune system has not yet learnt to defend anything. Only a minority of newborns become ill, but they become ill severely and very fast, and almost everything that protects them is decided in advance. So what follows is less about a disease than about preparing for the birth and about the first weeks at home.
Carrying it is not an infection
The bacterium is called Streptococcus agalactiae. It belongs among the normal inhabitants of the bowel, from where it passes easily into the vagina, and depending on the count it is found in ten to thirty women in every hundred. It causes no discharge, no itching and no smell: the only way to know it is there is a test.
One feature matters a great deal — carriage comes and goes by itself, so a swab describes not a person but a particular moment. Two practical things follow. First, a positive result from early pregnancy may mean nothing by the day of the birth, and a negative one taken too soon protects against nothing. Second, taking a course of antibiotics in advance is pointless: the bacterium returns within a few weeks, the mother's gut takes an unnecessary course, and the baby is no safer. What works is the antibiotic given during labour itself.
A separate case is group B streptococcus found in a pregnant woman's urine. That is no longer carriage but a urinary infection: it is treated the way such an infection is normally treated, and the woman also joins those who must have the antibiotic in labour, whatever later swabs may show.
How it is discovered
The test is simple: a swab is taken from the vagina and from the rectum — both places, because otherwise half of the women carrying it are missed — and grown on a culture medium. It is done in the last weeks of pregnancy, close to the due date, so that the result is fresh. Some maternity units also have a rapid test that can be run during labour and answers within an hour.
Who is offered that swab, however, depends on the country. There are two approaches and both are regarded as acceptable: in some places the test is offered to every pregnant woman, in others only to women with risk factors, and the decision about protection in labour is made on those factors instead. Neither is the single correct answer, so it is worth asking the midwife or doctor outright how it is done where you are booked, and what will count as a reason to give you the antibiotic.
Circumstances that raise the risk in their own right:
- labour has started before term;
- the waters broke well before the birth, particularly if more than eighteen hours have passed;
- the mother has a temperature during labour;
- group B streptococcus has been grown from urine in this pregnancy;
- a previous baby had an infection caused by this bacterium.
The antibiotic in labour, and why the timing matters
The protection itself looks thoroughly routine: a drip is put up in labour and an antibiotic of the penicillin group is given, or, if there is an allergy, a drug from another family chosen by the doctor. The point is for the medicine to have reached the baby's blood by the time of the birth. That is why time counts here: the earlier it is started after labour begins the better, and the aim is usually to have at least a few hours before delivery.
From this follows the one thing that genuinely depends on the woman herself — ring the maternity unit as soon as contractions start or the waters break, and mention the streptococcus straight away rather than waiting to be asked. Staying at home until the contractions "settle into a pattern", knowing you carry it, is not a good plan: that wait is exactly where the margin is lost.
A few questions come up again and again. For a planned caesarean, with labour not started and the membranes intact, no antibiotic is needed for the streptococcus. Breastfeeding is not affected in the slightest, and carriage is no reason to separate a mother from her baby. And carriage on its own does not dictate where or how you give birth: the only thing that changes is that you will have a drip.
Signs of infection in a newborn
Most often the infection shows itself within the first twenty-four hours of life, less often across the first week. There is also a late form, appearing between one week and three months, seen in babies of mothers who never carried it, and more often presenting as meningitis. So the signs are worth knowing after you go home too.
A baby needs to be seen immediately if any one of these appears:
- floppiness, unusual sleepiness, difficulty waking the baby, or a response that is simply not the usual one;
- grunting with each breath, drawing in under the ribs, breathing far too fast or too slowly, pauses in breathing;
- a temperature above or below normal — in a baby a low temperature is as worrying as a high one;
- pale, grey, mottled or bluish skin;
- refusing the breast or the bottle, repeated vomiting;
- a heartbeat that is far too fast or far too slow;
- a continuous high-pitched cry, irritability that will not settle;
- a tense or bulging fontanelle, the head arching back, fits or twitching;
- a rash that does not fade when a clear glass is pressed against it.
This is a situation measured in hours, so call an ambulance — across Europe the emergency number is 112 — or take the baby to the emergency department, but not at the wheel yourself: let someone else drive. Say at once that group B streptococcus was found during the pregnancy, because the choice of treatment depends on it. In hospital the baby will have blood tests, a lumbar puncture if needed, and intravenous antibiotics started without waiting for the culture to come back.
What happens afterwards
Most babies treated in time recover completely and grow up like anyone else. The severe forms — blood infection, pneumonia and meningitis — are dangerous precisely because they unfold in hours rather than days; after meningitis some children are left with lasting effects, most often hearing loss and, less commonly, delayed development, seizures or problems with sight. That is why hearing is always checked after meningitis and the child is followed up for a while. The infection can also kill a baby, and it is more honest to say so plainly: that is why so much caution has been built around what is, in itself, an ordinary bacterium.
The figures are best held whole, though. Without an antibiotic in labour, roughly one or two babies in every hundred born to a woman carrying it fall ill; with one, the risk of the early form drops several times over. In other words, even with no prevention at all the great majority of babies stay well — and prevention makes that likelihood very small indeed. There is as yet no group B streptococcus vaccine for pregnant women; one is being trialled, and when it arrives this whole arrangement will probably change.
Who else this bacterium troubles
Group B streptococcus is usually mentioned only in connection with childbirth, yet it also causes infections in adults, mainly in older people and in those whose defences are weakened: diabetes, especially with damage to the feet, cancer, recent chemotherapy, cirrhosis, long-term medicines that damp down immunity. It shows itself in various ways — infection of the skin and soft tissues, urinary infection, inflammation of a joint or a bone and, less often, infection of the blood. What should prompt attention is a red painful patch spreading quickly, particularly on the leg of someone with diabetes, an ulcer that will not close with swelling around it, and any of these together with shivering and a high temperature. In an older person a serious infection often looks atypical: no high fever, but confusion, weakness and a sudden loss of appetite.
Online consultation
A remote appointment deals well with exactly the questions that tend to go unanswered between visits. The doctor can explain what your swab or urine culture result means, whether to ask for the test if it has not been offered, and how protection in labour is organised where you are booked; and can help you put together a short note for the maternity unit, so that nothing has to be recalled at the wrong moment. After you are home, it is a convenient way to work out what you are actually seeing in your baby: the ordinary sleepiness of a newborn, or the kind that means leaving the house now. One exception: the signs of infection listed above are not assessed by video — with those you call an ambulance straight away.
This material is for information only and does not replace medical advice.
Consult with a doctor about Group B streptococcus
Discuss your symptoms and possible next steps with a doctor online.
Online doctors for Group B streptococcus
Discuss your symptoms and possible next steps for Group B streptococcus with a doctor online.
