Group B Strep and pregnancy

In rare cases the Group B Strep bacteria can cause complications in pregnancy and birth.

What is Group B Strep?

Group B Strep (GBS) is a common type of bacteria; about 20% of women in the UK carry it. It is found in the vagina and bowel and is usually not harmful to women that carry it. It is very natural and normal to carry the GBS bacteria and it’s not associated with any health risks for the carrier.

As the GBS bacteria can live in the vagina babies can come into contact with GBS after waters break and during the process of giving birth. Most will be unaffected, but a small number of babies (around 1 in 2000) can develop an infection as a result.

Symptoms of Group B Strep

The GBS bacteria do not produce any symptoms in women during pregnancy.

GBS infection in newborn babies

Most (two thirds) of the GBS infections in babies are early-onset, which means that the infection occurs in the first week of the baby’s life, typically in the first 12 hours after birth. Late-onset GBS can occur seven days to three months after birth.

Most babies who become infected can be treated quickly and successfully. For some babies however, complications can develop as a result of the infection. These include blood poisoning (septicaemia), infection of the lung (pneumonia) and infection of the lining of the brain (meningitis). In the long term it can cause deafness, blindness, learning difficulties and cerebral palsy. Around 1 in 10 babies who have developed a GBS infection will die. Overall this is 1 in 17,000 babies born in UK and Ireland.

Is my baby at risk of GBS infection?

GBS infection is more likely if:

  • your baby is born prematurely, (before 37 weeks of pregnancy)
  • you have previously had a baby who developed GBS infection
  • you have a high temperature during labour
  • more than 18 hours have passed between your waters breaking and your baby being born.

Treatment for Group B Strep infection

Taking the risk factors above into account, NICE guidelines say that if you have any one of the following:

  • If you have had a baby before who has been infected with GBS
  • If you have had a test during any point in your current pregnancy that has shown you carry GBS

And/or if you have any two of the following:

  • If your waters break or you go into labour before 37 weeks of pregnancy
  • If your waters have broken for more than 18 hours by the time you have your baby
  • If you have a raised temperature in labour of more than 38⁰C during labour

You will be offered antibiotics during labour to help to prevent your baby from getting the infection. The antibiotics can’t be taken before labour because the bacteria grows back very quickly and the protective effect may be gone by the time you give birth if you took them too soon. They are normally offered through intravenously (IV) for 15-30 minutes every four hours.

If your waters break after 37 weeks’ of pregnancy then you will also be offered for your labour to be induced straight away rather than waiting for a period of time to see if you go into labour naturally.

Antibiotics specific to treating GBS are not offered if you are having a planned caesarean section because the bacteria lives in the vagina and the baby will not come into contact with it as long as your waters have not broken before the caesarean section.

GBS and water births

Water births have not been shown to make infection more likely and as the antibiotics are given every four hours it should be physically possible. However some hospitals are still reluctant to allow them, possibly because of the added complication of having a cannula in your arm for the IV. Therefore it will be highly dependent on your hospital and care team whether you can still have a water birth if you are being treated for GBS infection.

Find out more about having a water birth.

Treating GBS in a newborn baby

After your baby has been born they will be closely monitored for signs of infection. Most babies who are infected with GBS will show symptoms within 12 hours of being born. Your baby’s heart rate, respiratory rate and temperature will be checked regularly. Your baby’s general health will also be monitored. Health professionals will look at how well your baby is feeding, whether they are floppy or overly sleepy and how well they are breathing and settling. If there are any concerns about your baby’s wellbeing then they will be seen by a neonatal doctor.

If GBS infection is suspected then tests will be carried out. These could be blood tests or testing some fluid from around your baby’s spinal cord. They will be fully discussed with you at the time. It will be advised for your baby to have antibiotics straight away, even before test results are available. If the test results come back as negative or the baby no longer has any symptoms for 24 hours then the antibiotics will be stopped.
Whether or not your baby has a GBS infection, it is completely safe to continue to breastfeed.

Symptoms of GBS infection in babies

Some symptoms of GBS infection in babies include:

  • High or low temperature
  • Fast or slow heart rate
  • Not feeding well
  • Limpness or difficult to wake
  • Difficulty breathing
  • Grunting

Testing for GBS in pregnancy

At present, not every pregnant women in the UK is offered testing for GBS on the NHS. Only women who have risk factors above are offered testing and/or antibiotics.

If you are offered a test in pregnancy, then this is usually done by a vaginal swab, though it can also be detected in your urine.

If you have had a swab that shows that GBS is present, treatment (antibiotics) will still be held until labour. This is because the antibiotics in pregnancy will not reduce the chance of GBS being passed to your baby and GBS can return after the course of antibiotics has been finished. If, however, you develop a urine infection during pregnancy that has shown to be caused by GBS, then you will be offered antibiotics straight away to treat the infection.

Some women choose to pay to have a test privately if they don’t meet the criteria to be offered it on the NHS. If you are thinking about this, talk with your midwife so you can discuss your options first. If you decide to go through with the test, the best time to have it done is between 35-37 weeks’ of pregnancy. GBS can move around the gut and the test is only valid for about five weeks after it was taken. If the test is done earlier than this, it may not be valid by the time you go into labour.

Types of tests

There are different types of tests that can be used to detect GBS in pregnancy. The two main tests available in the UK are the Standard Direct Plating and the Enriched Culture Medium (ECM).

If you are offered testing through your NHS care it is likely to be the Standard Direct Plating test. A vaginal swab will be taken and sent to the laboratory, you should get results back a couple of days later.

A positive result is very reliable and will be recorded in your maternity notes; no matter how many weeks’ pregnant you are when the test was done.
If you receive a negative result, no further action will be taken. It is possible to have a negative result but still be carrying GBS, but a repeat test would only be offered if you have developed risk factors in your pregnancy or labour.

The ECM test is not widely available on the NHS so most women would need to pay for this test privately. This test involves having two swabs taken, one vaginal and one rectal. These are sent away to a laboratory and you can expect to get the results back a few days later. This test is more sensitive at identifying GBS but it is not as effective at identifying other potential bacteria and viruses that maybe present and can still give a false result.

Why is GBS not routinely screened for?

Testing for GBS in pregnancy is often debated and these are the reasons given by the UK National Screening Committee and RCOG as to why testing is not currently offered as a routine to all pregnant women in the UK:

  • Currently there is no clear evidence that routine screening would do more good than harm
  • Many women carry the bacteria and, in the majority of cases, their babies are born safely and without developing an infection.
  • Screening all women late in pregnancy cannot predict which babies will develop GBS infection.
  • No screening test is entirely accurate. A negative swab test does not guarantee that you are not a carrier of GBS. In other words, you may be given a negative result when in fact you do carry GBS.
  • The majority of babies who are severely affected from GBS infection are born prematurely, before the suggested screening test would have happened.
  • Giving all carriers of GBS antibiotics would mean that a very large number of women at very low risk would receive treatment they do not need.
  • There is a risk to the general public from overuse of antibiotics leading to strains of bacteria becoming resistant.
  • The long term effects of antibiotic treatment in labour on the baby are unknown.
  • The amount of babies affected by GBS in the UK is the same as that in countries in which testing is a routine part of antenatal care.


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    Last reviewed on June 30th, 2017. Next review date June 30th, 2020.

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