Group B Streptococcus in pregnancy
What is Group B Streptococcus?
Group B Streptococcus (GBS), also known as group B strep, Streptococcus agalactiae, Strep B, or Beta Strep, is a type of bacteria commonly found in the digestive and lower reproductive tracts of both men and women.
How do you get GBS in the vagina?
GBS is commonly found in the vagina with about 1 in 4 pregnant women testing positive for the bacteria. It is not a sexually transmitted infection, although it can be passed between partners by sexual intercourse. GBS colonisation has been found to be more prevalent in women with diabetes or who are obese.
What are the symptoms of GBS in pregnancy?
GBS does not cause any symptoms in the mother if it stays in the vagina or rectum, as it cannot cause infection in these sites. It can however cause a urinary tract infection, with symptoms including pain on passing urine, passing urine more frequently, having to rush to go to the toilet, or cloudy smelly urine.
How do you know if you have GBS in pregnancy?
To test for GBS you will need to have a swab of both the vagina and rectum. This should be done 3-5 weeks prior to delivery. In an uncomplicated pregnancy the testing would therefore be done at 35-37 weeks gestation, but if an earlier delivery is anticipated then testing would need to be brought forward. Testing will be carried out by the NHS on all women who tested positive for GBS in a previous pregnancy.
The NHS does not conduct routine screening of women for GBS in pregnancy, and there is a lack of consistency around the world. At least 60 countries have a policy for antibiotic use in pregnancy to prevent newborn GBS disease, the NHS included. Unlike the NHS, 35 have a policy to test all pregnant women to see if they carry GBS, and the remaining 25 countries identify women with clinical risk factors.
The reasons given by the NHS for not screening are:
Many women carry the bacteria and, in the majority of cases, their babies are born safely and without developing an infection.
Screening women late in pregnancy cannot accurately predict which babies will develop GBS infection.
No screening test is entirely accurate. Between 17% and 25% of women who have a positive swab at 35–37 weeks of gestation will be GBS negative at delivery. Between 5% and 7% of women who are GBS negative at 35–37 weeks of gestation will be GBS positive at delivery.
In addition, many of the babies who are severely affected from GBS infection are born prematurely, before the suggested time for screening.
Giving all carriers of GBS IAP would mean that a very large number of women would receive treatment they do not need; this may increase adverse outcomes to mother and baby (see sections below).
The NHS does recommend that some women will decide to test privately, and they will recognise a private test result as being equivalent to one performed in the NHS as long as it is from a reputable laboratory. At Sirona Health we can provide private testing kits with the assurance that the results are accurate and accepted by your local obstetric team.
Who requires antibiotics during labour?
A woman having a planned Caesarean section doesn’t need IV antibiotics specifically for GBS, as long as her waters haven’t broken and she’s not in labour.
A woman should be offered antibiotics effective against GBS in labour if she:
had a previous baby who had GBS infection.
had GBS in her urine during the pregnancy.
had GBS detected on a vaginal or rectal swab.
carried GBS in a previous pregnancy and has declined testing this pregnancy.
is in preterm labour (before 37 completed weeks of pregnancy).
has a temperature of 38°C or greater (in which case, offer broad-spectrum antibiotics that also cover GBS).
What are the symptoms of GBS infection in the baby?
Group B Streptococcus (also known as Group B Strep or GBS) is the most common cause of severe infection in newborn babies, and usually shows in the first hours and days of life. In babies aged between 0-3 months, GBS infection often presents as sepsis, pneumonia or meningitis.
Grunting, noisy breathing, moaning, seems to be working hard to breathe when you look at the chest or tummy, or not breathing at all
Being very sleepy and/or unresponsive
Inconsolable crying
Being unusually floppy
Not feeding well or not keeping milk down
A high or low temperature, and/or hot or cold to the touch
Changes in their skin colour (including blotchy skin)
An abnormally fast or slow heart rate or breathing
Early-onset group B Strep infection occurs in the first 6 days of life, most showing signs of infection within 12 hours of birth. If the mother has tested positive or had a positive test in a previous pregnancy, well babies should be evaluated at birth for clinical indicators of neonatal infection and have their vital signs checked at 0, 1 and 2 hours, and then 2 hourly until 12 hours.
Late-onset group B Strep infection occurs after a baby’s first six days of life, is uncommon after a month and very rare after three months.
Being irritable with high pitched or whimpering cry, or moaning;
Blank, staring or trance-like expression;
Floppy, may dislike being handled, being fretful;
Tense or bulging fontanelle (soft spot on babies’ heads);
Turning away from bright light;
Involuntary stiff body or jerking movements; and/or
Pale, blotchy skin.
Effect on the baby’s microbiome
Several studies have shown an effect of intravenous antibiotics given to the mother on neonatal bowel flora, for example, causing reductions in colonisation with lactobacilli or bifidobacterium, but these findings have not been consistent across all studies. Changes in the neonatal bowel microbiome have been linked to several later effects in the child, including allergy, and obesity and diabetes. However, this is still a very new area of scientific research and the impact of treating GBS during labour on the baby’s microbiome, and the long-term impacts, are still largely unknown.
What is on the horizon?
There are currently trials underway for the development of a GBS vaccination which can be given to pregnant women and prevent the transmission of GBS to the baby. We are still quite a long way off this becoming a reality, but the hope is that it will result in a significant reduction in GBS infection without requiring the use of antibiotics.
“An effective maternal Group B Strep vaccine deployed worldwide could prevent tens of thousands of newborn deaths and stillbirths each year” Dr Simon Procter Research Fellow London School of Hygiene and Tropical Medicine.
References
Prevention of Early-onset Neonatal Group B Streptococcal Disease: Green-top Guideline No. 36. BJOG. 2017 Nov;124(12):e280-e305. doi: 10.1111/1471-0528.14821. Epub 2017 Sep 13. PMID: 28901693.
Diamond L, Wine R, Morris SK. Impact of intrapartum antibiotics on the infant gastrointestinal microbiome: a narrative review. Arch Dis Child. 2022 Jul;107(7):627-634. doi: 10.1136/archdischild-2021-322590. Epub 2021 Oct 29. PMID: 34716171.