This article is aimed at women with GBS positive status in current or past pregnancy, or as information in case of prelabour rupture of membranes.
For whatever reason, it is sometimes the case that a woman has a vaginal swab taken during pregnancy. One of the things routinely tested for is Group B Streptococcus. Should you have a positive test, please first be reassured that this is not an infection. It is a normal part of the gut flora of a third of people and a quarter of women will be carrying it in their vagina at any given time. It is transient, and colonisation in early pregnancy is not an indicator of colonisation at time of birth. There is also a sharp increase in the rate of positive GBS tests in the hours after sex. If you recently had sex before the swab was taken, you may only be temporarily carrying your partner’s GBS. The reason for concern is that at present, GBS is the main cause of birth infection and GBS disease in a neonate is fatal in 10% of cases.
Whatever the circumstances that led you to have a swab taken, the professional outcome tends to be the same – “Oh it’s nothing to worry about, you just need to come into hospital when labour starts for IV antibiotics”; “But I’m planning a homebirth…” Do not despair; a GBS+ homebirth is entirely feasible.
GBS risk factors and guidelines
GBS is the most common cause of birth infection in the UK, taking over from E. coli which was the primary agent in the 1950s. Early onset (within 7 days of birth, usually within 24 hours) is generally considered to come from the mother. Late onset (more than 7 days) is usually considered to be picked up from the environment (poor hygiene: hospital or personal). The current rates of infection are 0.5/1000 for a baby to suffer GBS infection; 0.9/1000 for past pregnancy GBS+ status; and 2.3/1000 in current pregnancy GBS carriers.
Here are the main risk factors for GBS birth infection:
• Preterm babies
• Mother having a fever during labour (by far the riskiest category)
• Prolonged rupture of membranes – over 18 hours
• GBS found in the mother’s urine, not just the vagina
• Mother having had a previous child with GBS disease
• Rupture of membranes before 37 weeks
(Taken from http://www.homebirth.org.uk/gbs.htm)
The current Royal College of Obstetricians and Gynaecologists (RCOG) guidelines are linked at the bottom of the article. Some pertinent points are summarised below:
• Routine antenatal screening for GBS is not recommended.
• In the case of a positive swab in pregnancy, antenatal antibiotics are not recommended but should be offered during birth.
• Screening and antibiotics in pregnancy are not recommended for women who have positive carrier status in previous pregnancies.
• GBS infection identified in urine should be treated with antibiotics during pregnancy and birth.
• NICE guidelines are such that induction of labour should be offered to all women with prelabour rupture of membranes at term (37 weeks +) over 24 hours; for GBS carriers this is recommended immediately.
• Women in term labour with rupture of membranes should not be offered antibiotics without other risk factors present.
• Women in labour with a temperature above 38C should be offered antibiotics.
• Women in established preterm labour, with intact membranes, with no established GBS carrier status, should not be routinely offered antibiotics.
• Women in preterm labour with rupture of membranes should not be offered antibiotics ‘just in case’.
• Antibiotics should be offered to women who have had previous infants with GBS disease. There is no need for a swab as this recommendation would stand regardless.
In practice, it is seems most hospitals recommend coming into hospital as soon as labour starts and giving IV antibiotics, regardless of other risk factors. The reason for this keenness is because evidence shows that antibiotics provided later than 4 hours before delivery are likely to be ineffective. However, evidence also shows that routine administration of antibiotics does not reduce the GBS nor overall birth infection mortality rate, nor infection from other agents; whilst studies do show a reduction in incidence of GBS, there is concern over the validity of this data (see Cochrane review). In the US, where there is systematic GBS screening and antibiotics for all GBS+ women, the rate of GBS disease has reduced but only to be replaced by resistant E. coli. The overall birth infection and mortality rate (from all causative agents) remains the same.
What are the risks to the baby?
In a 2010 study (Vergnano et al) 82% of all birth infection occurred in babies born before 37 weeks; 71% was in babies born before 32 weeks. 58% of the total early onset (
Given the evidence from the US and the statistics separating preterm and term babies, it seems that the common factor here is vulnerable babies vs healthy, fully developed babies. Your own personal circumstances will colour how you feel about this; though as a prospective homebirther, it’s perhaps likely that you will have considered and ruled out potential vulnerabilities in your baby.
It’s important to weigh up the risks of GBS infection against the risks of IV antibiotics. Neonates born to mothers who received antibiotics during labour are likely to be colonised only by bacteria species and strains that are resistant to the antibiotics used. There is no research examining the effect this may have on the baby’s early or future health. Research connects exposure to antibiotics during the birth process to persistent wheezing in childhood and other studies showed that the initial colonisation of the newborn intestine with normal bacteria persists over a long period and has a pivotal effect on long term health. People obtain 90% of their gut flora from their mothers, during birth. The remaining 10% is fixed during the first 6 months of life, from breastfeeding and/or environmental sources. It cannot be permanently changed after this age.
There is a risk of maternal anaphylaxis. There is also a risk to the mother’s own gut health and the biota of her breastmilk until her body returns to normality.
If you wish to treat the GBS (perhaps you have a history of GBS infection) there are alternatives to antibiotics that you can try. There is some evidence that birthing in water may reduce the likelihood of infection in the baby. Eating a low-sugar, healthy, diet can help maintain a healthy pH in the vagina which allows ‘good’ bacteria to outcompete any threatening types (also Candida). Taking probiotic supplements such as Acidophilus may also support the gut flora. There are various vaginal treatments that can be attempted: some evidence shows that two chlorhexidine douches during labour will remove 90% of the vaginal flora (non-discriminately), though in the RCOG guidelines, chlorhexidine efficacy is questioned. Garlic and live yoghurt ‘pessaries’ may support suppression of GBS and promote growth of safer bacteria. Avoid sex as you near term and certainly if your waters have broken. A swab taken after 36 weeks will give an approx. 80% indication of colonisation at the time of labour. If you are concerned, you could try these methods and then pay for a private swab (the NHS swab has a high rate of false negatives) at 36 weeks.
After the birth
Regardless of the actions you choose to take, it is important (for all parents) to ask your midwife about how to monitor your baby for signs of infection.
Other Studies on affects of antibiotics:
An AIMS article on GBS: War on Group B Strep
There are a number of suggestions in this archive of GBS posts.
Written by Pamela, mum of 2 who birthed at home after a positive GBS result