Group B Streptococcus | Why you should get tested for this during pregnancy

Posted on April 5th, 2018

This common bacteria that many moms carry can place their newborn in danger. Here’s what you need to know. By Kate Sidley

Group B Streptococcus

What is Group B Strep?

GBS stands for Group B Streptococcus. This bacterium can colonise the human genital and gastrointestinal tracts in low numbers.
It’s quite common and most carriers don’t have symptoms or illnesses due to GBS colonisation. According to Dr Olga Perovic, principal pathologist at the National Institute for Communicable Diseases (NICD), GBS has been isolated from the genital or lower gastrointestinal tracts of pregnant and non-pregnant women at rates ranging from 10% – 40%.
She adds that GBS colonisation is more prevalent among black women that other racial or ethnic groups, and that diabetes is an independent risk factor.

ALSO SEE: Your guide to antenatal checks

There are three types of GBS disease
  • Prenatal onset – The baby’s infected during pregnancy.
  • Early onset – From birth, during delivery to one week.
  • Late onset – From one week to several months old.

Are you a GBS carrier?

Most women aren’t aware that they carry GBS bacteria. Although it can cause bladder or uterine infections in pregnant women, mostly there are no symptoms.
To find out whether a mom-to-be is a carrier, a swab of the vaginal and rectal areas is taken at 35-37 weeks of gestation. The sample is sent to a laboratory, where a culture is analysed for the presence of GBS bacteria. A negative test result early on doesn’t exclude the possibility of acquiring the organism later in the pregnancy.

How is the baby infected?

GBS can infect the baby during pregnancy. More commonly, transmission takes place during delivery when the baby is exposed to the vaginal mucous membrane that contains the bacteria. GBS in the vagina or rectum could colonise the newborn.

ALSO SEE: 11 reasons why your gynae might insist that you have a C-section

Signs and symptoms

Symptoms of early-onset GBS infection in a newborn usually present within the first day of life. They include:

  • Being unresponsive, lethargic or floppy
  • Poor feeding
  • Fast or slow hear rate
  • Fever
  • Difficulty breathing

Samples of blood and/or spinal fluid will be taken to confirm diagnosis, but if a baby shows signs of GBS, treatment will be administered in the hospital immediately.

Should I be concerned?

  • Most GBS carriers give birth to healthy babies. Even when the mom is colonised with GBS, the risk of the baby developing the disease is about 1:200.
  • Although the risk is low, GBS is seen as an important pathogen during pregnancy. When a mom-to-be has high levels of GBS, she runs a higher risk of preterm labour.
  • GBS in the mother can also cause miscarriage and stillbirth. It’s also the leading cause of sepsis and bacterial meningitis in newborns, states the Centre for Disease Control and Prevention (CDC) in the USA.
  • Neonatal infections like septicaemia (blood poisoning) and pneumonia (lung infection), can be life threatening. It can also cause permanent brain damage, such as when the newborn gets meningitis (infection of the brain lining).

Can I prevent my baby from getting GBS?

Dr Perovic says that there are two ways to prevent GBS infections in newborns. One is to take a culture at 35 to 37 weeks of gestation. This is seen as a common practice in some developed countries.
The other is a risk based approach, where the mother falls into a high-risk category for GBS colonisation or infection. This includes when a pregnant woman has had a GBS infection before, the membrane has ruptured during pregnancy, or when the mother has diabetes (and is tested and treated accordingly).
In the case of GBS colonisation, penicillin is prescribed to the mother if she’s not allergic to the agent. Because the bacteria can grow back quickly, it’s not effective to treat the mother during the early stages of pregnancy. Therefore, penicillin is given via a drip during labour.
If a woman’s tested positive for GBS and isn’t in the high-risk category, the chances of having a baby with GBS drops to 1:4000 (from 1:200 without antibiotics), according to CDC figures.

Note: Group B Streptococcus is not the same bacterium that causes strep throat.


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