Group B Strep and pregnancy

Group B Streptococcus (Group B Strep, Strep B, Beta Strep, or GBS) is a type of bacteria which lives in the intestines, rectum and vagina of around 2-4 in every 10 women in the UK (20-40%). This is often referred to as ‘carrying’ or being ‘colonised with’ GBS.

Group B Strep is not a sexually transmitted disease. Most women carrying GBS will have no symptoms. Carrying GBS is not harmful to you, but it can affect your baby around the time of birth.

GBS can occasionally cause serious infection in young babies and, very rarely, during pregnancy before labour.

The information below is for you, a friend or a relative who is expecting a baby, planning to become pregnant or has recently had a baby. 

How do people become carriers of group B Strep?

Like many bacteria, 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 can be passed through sexual contact.

There are no known harmful effects of carriage itself and 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. Around 20-40% of women carry GBS.

GBS may be passed from one person to another by skin-to-skin contact. Everyone (regardless of whether they know they carry GBS) should wash their hands properly and dry them properly before handling a newborn baby.

How is group B Strep found?

Most women carrying GBS have no symptoms, so GBS is often found by chance through a vaginal or rectal swab test or a urine test.

The NHS does not routinely test all pregnant women for group B Strep.

Tests designed specifically to find GBS carriage, known as the Enriched Culture Medium (ECM) test, are increasingly becoming available within the NHS and are widely available privately.

Since September 2017, the Royal College of Obstetricians & Gynaecologists (RCOG) has recommended in their guideline on group B Strep that selected pregnant women should be offered the ECM test. Many maternity units still use a standard test that misses up to half of the women carrying group B Strep, so ask your health professionals what is available locally.

There are private home ECM testing kits for GBS carriage you can order.

What could group B Strep mean for my baby?

Many babies come into contact with group B Strep during labour, or around or after birth and the vast majority will not become ill.

However, there is a small chance that your newborn baby will develop group B Strep infection and become seriously ill, or even die, and this chance is increased if you are carrying GBS.

The infections that group B Strep most commonly causes in newborn babies are sepsis (infection of the blood), pneumonia (infection in the lungs), and meningitis (infection of the fluid and lining around the brain).

Around 1 in every 1750 babies in the UK and Ireland is diagnosed with early-onset group B Strep infection (developing in babies aged 0-6 days).

Around 1 in every 2700 babies in the UK and Ireland is diagnosed with late-onset group B Strep infection (developing in babies aged 7-90 days).

Although group B Strep infection can make your baby very unwell, with prompt treatment most babies will recover fully.

Of the babies who develop GBS infection, 1 in 19 (5.2%) will die from early-onset GBS infection and 1 in 13 (7.7%) from late-onset GBS infection. Of those who survive their GBS infection, 1 in 14 (7.4%) will have a long-term disability following early-onset GBS infection and 1 in 8 (12.4%) following late-onset GBS infection.

Is my baby at risk of group B Strep infection?

Any baby can develop a group B Strep infection, but early-onset group B Strep infection (developing in the first 6 days of life, and usually on the first day of life) is more likely if:

• your baby is born preterm (before 37 weeks of pregnancy) – the earlier your baby is born, the greater the risk
• you have previously had a baby who developed a group B Strep infection
• you have had a high temperature (or other signs of infection) during labour
• you have had any group B Strep positive urine or swab test in this pregnancy
• your waters have broken more than 24 hours before your baby is born

Late-onset group B Strep infection (developing in babies aged 7-90 days) is less common than early-onset GBS infection and is more likely if:

• your baby is born preterm (before 37 weeks of pregnancy)
• you have had group B Strep positive test in this pregnancy

How can the risk to my baby be reduced?

Most early-onset group B Strep infection can be prevented by giving intravenous antibiotics in labour to women whose babies are at raised risk of developing the infection. At present, there are no known methods to prevent late-onset GBS infection.

• A urine infection caused by group B Strep should be treated with antibiotic tablets straight away and you should also be offered intravenous (IV) antibiotics during labour.
• You should be offered IV antibiotics during labour if you have had a GBS-positive swab or urine test from an NHS or other accredited laboratories (see www.gbss.org.uk/test).
• If you have previously had a baby who was diagnosed with GBS infection, you should be offered IV antibiotics when you are in labour.
• If GBS was found in a previous pregnancy and your baby was unaffected, you can have a specific swab test (known as the ECM test) to see whether you are carrying GBS when you are 35-37 weeks pregnant. If the test result is positive, you will be offered antibiotics in labour. If the ECM test result is negative at this point, then the risk of your baby developing early-onset GBS infection is low and you may choose not to have antibiotics.
• If your waters break after 37 weeks of your pregnancy and you are known to carry GBS, you will be offered induction of labour straight away. This is to reduce the time that your baby is exposed to GBS before birth. You should also be offered IV antibiotics.
• Even if you are not known to carry GBS, if you develop any signs of infection in labour, you will be offered IV antibiotics that will treat a wide range of infections including GBS.
• If your labour starts before 37 weeks of your pregnancy, your healthcare professional will recommend that you have IV antibiotics even if you are not known to carry GBS.

At present, there are no known methods to prevent late-onset GBS infection, so knowledge of the typical signs of infection is vital.

If you are worried about your baby, you should urgently contact your healthcare professional and mention any history of GBS when you do.

Related pages

Where to order a group B Strep test

What does my test result mean?

After your baby is born