GBS screening

INFORMATION SHEET

Making a decision about prenatal GBS testing

Your midwife or doctor may recommend that you have a test in late pregnancy to determine whether or not you have a particular bacteria, known as group B Streptococcus, or GBS, in your vagina and anus.  This Q&A is designed to give you factual information about GBS screening, to assist you in making an informed decision.

Q.        What will happen if my baby develops GBS infection?

A.        The purpose of both ‘screen and treat’ and ‘risk factor’ protocols (see below) is to prevent early onset GBS in the newborn baby.  A baby who develops a GBS infection may quickly become very ill, and requires expert neonatal services that include assessment, treatment, and observation from a skilled team of doctors, nurses and other services such as pathology and X ray.

Q.        Is there any risk to my baby if I have antibiotic treatment in labour?

A.        Antibiotics should not be used without a good reason.  The potential side effects of antibiotic treatment include altered colonization of the baby’s skin and digestive tract.  Discuss the potential risk and benefits of the treatment protocol that is recommended to you with well informed professional care providers.

Q.        I don’t feel unwell, so why would I need to be tested for this bacteria?

A.        It is estimated that one in four pregnant women will return positive GBS swabs.  The presence of GBS in the genital tract usually produces no symptoms, and is not harmful, except during labour. 

Q.        How is the test performed?

A.        The test requires a small sterile swab to be placed into your vagina, then in your anus.  Your privacy is ensured, and a midwife will offer you the choice to swab yourself, or to do it for you.  The swab is then placed in a special medium in a test tube; labeled carefully, and sent to the laboratory.

Q.        When is the test performed?

A.        Between 35 and 37 weeks’ gestation.  Screening cultures take 24-48 hours to become positive, so this test is not useful once labour has started.

Q.        Is there any way that I can eradicate GBS from my genital region?

A.        There is no evidence that treatments to eradicate GBS lead to improved outcomes, such as reduced rates of GBS infection in the mother or baby.

Q.        What will happen if I have a positive GBS test?

A.        The purpose of this screening test is to identify any pregnant woman who has GBS, so that antibiotic treatment can be started in early labour, at least four hours before the baby is born, or when the waters break, and continued until the baby has been born.  This plan is called ‘screen and treat’.  The antibiotics are usually given intravenously, via a cannula in your arm. 

Q.        What will happen if I decide not to have the GBS test?

A.        When the GBS status is unknown, your midwife will observe for risk factors that would indicate the likelihood of GBS infection, and advise you to have antibiotic treatment if any one of these factors presented.  This is called the ‘clinical risk factor’ in labour approach.  The risk factors are: labour starting at or before 37 weeks’ gestation; rupture of membranes for 18 hours or more; maternal fever of 38C or more (usually accompanied by fetal tachycardia); previous GBS infected baby; or a positive GBS urine test during this pregnancy.

Q.        What will happen if my GBS test is negative?

A.        You will not receive antibiotics in labour, unless you develop one or more clinical risk factors.

Comment:

Midwifery imperatives of working in partnership with each woman, and the promotion of normal birth, as well as preventative measures, the detection of complications in mother and child, and the accessing of medical care when indicated (ICM 2011) are principles that guide my thinking as I engage in clinical assessment, discussion, and ongoing planning of care for each woman.  At all times the wellbeing and safety of mother and fetus/child are paramount.   

There is no clear, ‘black and white’ answer to the question of screening well women for GBS that will ensure safety and wellbeing.  In my practice I do not ask women to undergo screening. 

 
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