Group B Strep: The ultimate guide for pregnant women

Find out more about this common bacterial infection carried by a third of all pregnant women.

Pregnant mum
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Group B Strep is a common bacteria passed from the mother during labour, which can be potentially very dangerous for newborn babies.

What is group B Strep?

Group B Streptococcus, group B Strep, or GBS, is a bacterial infection. If not treated, it can cause meningitis, pneumonia or blood poisoning in newborn babies. It's a very common bacteria that lives in the intestines, vagina and rectum of about 20-40 percent of healthy women in the UK. GBS is not a sexually transmitted disease and does not usually cause harm in our own bodies. However, during labour or sometimes during pregnancy, women carrying the bacteria can pass it onto their baby.

What causes group B Strep in pregnancy?

GBS is a naturally occuring bacteria that comes and goes throughout our lives in both men and women. There is nothing that particularly causes GBS during pregnancy. "Many women have Group B Strep when they are pregnant and when they are not pregnant," explains Lesley Gilchrist, Registered Midwife and Founder of My Expert Midwife. "It is not generally something you would know you had unless you had been tested for it."

What are the symptoms of group B Strep?

Group B Strep does not have any symptoms, so most women who carry the bacteria aren't aware of it.

How do I know if I have group B Strep?

Group B Strep carriage can come and go, which is why the NHS does not routinely swab for GBS. You may pick up a positive result early on, but then not be carrying the bacteria by the time you give birth. A sensitive swab test at 35-37 weeks usually gives the best indication if a woman will carry GBS at delivery.

On the other hand, you may discover that you're carrying GBS during other routine tests, such as a urine sample or vaginal swab. If the midwife or doctor thinks there is cause for concern, they may then request a GBS test.

Can I get tested for group B Strep?

Yes. If you are worried about GBS, you can take an Enriched Culture Medium (ECM) test privately or in selected NHS hospitals. You can conduct a test at home using a reputable organisation recommended by the Group B Strep Support group, which usually costs around £38 with results available in a couple of days.

Anthonissa Moger, founder of The Hypnobirthing Midwife and author of Holistic Hypnobirthing warns that testing has its limits: "GBS is a normal microbe that around a third of all women carry in their bodies which causes no harm for most babies. It is tricky because it is transient so you can be positive for it one month and negative the next. If you are concerned you can order a private test around 37 weeks of pregnancy and if this comes back positive, ask the hospital to monitor your baby for 12-24 hours after birth for signs of infection."

"Deciding to be tested for Group B Strep is a personal decision," says My Expert Midwife, Lesley Gilchrist. "I recommend researching this thoroughly before deciding, as well as discussing your individual circumstances with your midwife or doctor."

Pregnant woman doctors test group b strep

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What are the chances of me passing it on to my baby?

The NHS reports that there's only a small risk of infecting your baby and making them ill, as this happens in about 1 in 1,750 pregnancies. Risk of death is even smaller. According to the University of Oxford Vaccine Knowledge Project,  only one in 17,000 babies in the UK die from GBS infection each year.

Most importantly, even if you carry group B Strep bacteria, your baby is most likely to be born safely. According to a report from the Shrewsbury and Telford Hospital NHS trust, out of every 20,000 newborn babies in the UK and Ireland, only 10 are diagnosed with neonatal GBS infection; of these 10, one baby will die. Overall, the risk of a baby dying from GBS is therefore 1 in 20,000, which means it is classed as rare.

Can I pass group B Strep onto my partner?

GBS is not a sexually transmitted disease and GBS bacteria do not spread through food or water. However, because GBS can be transmitted through skin-to-skin contact and it's often found in the vagina or rectum, it can be passed through sexual contact. Carrying GBS is perfectly natural; it's not a symptom of uncleanliness or poor hygiene, so it's nothing to be embarrassed about.

Can GBS be prevented?

Yes. If GBS is found in a urine sample you'll be prescribed oral antibiotics. If you've had a positive GBS test result during the current pregnancy, you should also be offered an antibiotic drip once labour starts and until the baby is delivered.

Some experts also recommend eating healthily to improve your gut health and avoid picking up GBS:

Should I have a C-section to prevent infecting my baby with GBS?

No, there is no evidence that having a caesarean section will necessarily protect against GBS infection. A C-section operation can also carry significant risks of its own, and should only be conducted when absolutely necessary.

"Carriage of GBS in itself would not be a reason to advise caesarean section," explains Dr Kate Navaratnam, NIHR academic clinical lecturer at the University of Liverpool and researcher at women's health research charity, Wellbeing of Women. "Vaginal birth, with appropriate antibiotics is a very safe approach. However, if a caesarean section is required for other reasons and you carry GBS, you do not need antibiotics unless labour has already started or your waters have broken. All women having a caesarean section are offered antibiotics to reduce the risk of a wide variety of infections."

crying baby

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Can vaginal seeding transmit GBS?

Vaginal seeding is thought to carry some risk of transmitting GBS, however it is still a relatively new practise and not enough is known about it. Vaginal seeding is where c-section newborns are swabbed with their mother's vaginal fluid on the face, body and mouth. This helps newborns pick up microbes they would have been exposed to during a vaginal birth to bolster the immune system.

Can I have a home birth if I carry GBS?

It may be more difficult to have a home birth if you are known to carry GBS. You should speak to your midwife or doctor to make the best decision for you and your baby.

Dr Kate Navaratnam, researcher at women's health charity, Wellbeing of Women, explains that: "Delivery in hospital is usually advised. This is because providing antibiotics via a drip may not be possible at home or in some midwifery led units. However, decisions on where to deliver are personal and options available will vary by locality.

"Where carriage of GBS is identified it is advisable to discuss options for place of birth with your midwife and obstetrician. You should enquire whether antibiotics could be provided outside the hospital setting when deciding on your birth plan."

What are the symptoms in babies?

Most babies born with Group B Strep develop tell-tale symptoms around 12-24 hours after birth. Symptoms include:

  • Being floppy and unresponsive
  • Not feeding well
  • Grunting
  • High or low temperature
  • Fast or slow heart rates
  • Fast or slow breathing rates
  • Irritability

When do babies get infected with GBS?

Group B Strep infection can happen immediately or in the first week of life (early-onset GBS) or within the first three months (late-onset GBS).

Late-0nset GBS is not usually associated with pregnancy or birth. Since it's a skin-contact infection it could have been picked up from someone else. You should therefore always ask friends and family to wash their hands before handling a newborn.

Baby IV tubes group b strep

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What treatment is there for babies?

Most babies infected with GBS can be successfully treated with a course of penicillin antibiotics. They may have intravenous antibiotics or fluids via IV to help with symptoms of GBS. In addition, if the baby has meningitis, they'll be prescribed a course of IV antibiotics for seven to 14 days.

What are the potential risks of antibiotics?

If you have ever suffered a serious reaction to antibiotics, it's very important that you tell your nurse, doctor or midwife.

You may be concerned about giving your newborn baby antibiotics. However, if group B Strep is present then antibiotics are necessary to prevent any more serious illness. This NHS report answers any questions you may have about giving your baby antibiotics.

Lisa Harris is a senior lifestyle writer, editor and food trends consultant with over 10 years experience in the industry. Her work is published on, as well as in The Guardian, The Sunday Times, Stylist, The Telegraph and the Independent. She is an official Time Out restaurant reviewer.