Group B Strep in Pregnancy

May 6

Group B Streptococcus (GBS) is a topic that often generates concern during pregnancy, particularly when it is presented without context or nuance. If you have recently learned about GBS or have been told you are carrying it, you may be navigating a mixture of uncertainty and worry. It is important to recognise that GBS is common, usually harmless in adults, and that evidence‑based care can significantly reduce the already low risks associated with it. Understanding the research can help you approach this topic with clarity and confidence.

GBS is a type of bacteria naturally found in the gastrointestinal and genital tracts. In the United Kingdom, approximately 20–30% of pregnant people carry GBS at any given time. This colonisation is transient, meaning that a person may test positive at one point in pregnancy and negative at another. This variability is one reason the UK does not routinely screen all pregnant people for GBS. Instead, the NHS follows a risk‑based approach, offering testing or intrapartum antibiotics when certain clinical factors are present.

The primary concern associated with GBS is early‑onset GBS disease (EOGBS) in newborns. Evidence Based Birth reports that the overall risk of a baby developing EOGBS in high‑income countries is approximately 0.5 per 1,000 births. In the UK, the rate is similar, with national surveillance data showing around 0.6 cases per 1,000 births. While the risk is low, it is not zero, and this is why GBS remains an important topic in maternity care. Understanding both the absolute risk and the context of that risk is essential for informed decision‑making.

When GBS is identified during pregnancy, the most common recommendation is intravenous antibiotics during labour. Research shows that intrapartum antibiotics reduce the risk of EOGBS by 80% or more, lowering the incidence to approximately 0.1 per 1,000 births. However, Evidence Based Birth highlights that antibiotics do not eliminate risk entirely, nor do they address late‑onset GBS disease, which occurs after the first week of life and is not prevented by antibiotics in labour. This distinction is important, as it underscores the need for balanced, evidence‑based conversations rather than assumptions that antibiotics are universally required.

Sara Wickham’s work encourages a deeper examination of the evidence behind routine interventions. She notes that while antibiotics can be beneficial in specific circumstances, they also carry potential downsides, including disruption of the newborn microbiome and increased maternal risk of antibiotic‑related side effects. Parents deserve full information about both benefits and limitations so they can make decisions aligned with their values and circumstances.

It is also important to recognise that GBS colonisation does not predict birth outcomes. Many people who carry GBS have uncomplicated labours and healthy babies. The bacteria itself is not harmful to the pregnant person, and most babies exposed to GBS during birth remain completely well. Evidence Based Birth highlights that the majority of babies who develop EOGBS are born to parents who tested negative or were never tested, illustrating the limitations of screening and the complexity of risk assessment.

If you have been told you carry GBS, you are entitled to ask questions and explore your options. You may wish to discuss the accuracy of testing, the timing of colonisation, the absolute versus relative risks, and the potential benefits and drawbacks of antibiotics in labour. You may also wish to consider your personal health history, your birth preferences, and the support available to you. Informed decision‑making is not about choosing the “right” option; it is about choosing the option that feels right for you, based on evidence and personal values.

Above all, remember that carrying GBS does not define your pregnancy or your birth. It is one factor among many, and with balanced information and supportive care, you can navigate this topic with confidence. Your body, your baby, and your choices matter, and you deserve care that honours your autonomy and respects the complexity of the evidence.