Pregnancy and Group B Streptococcal Infection

Group B streptococci (GBS), or Streptococcus agalactiae, are bacteria commonly found in the vagina, rectum or bladder.

Normally present in the digestive tract, group B streptococcus is not pathogenic. However, this bacterium can sometimes colonise the genital area of expectant mothers — and this is where it becomes dangerous. Group B streptococcus can then be transmitted to the foetus during pregnancy, as well as during labour[1]. Screening is carried out by means of a vaginal swab between 34 and 37 weeks of pregnancy.

What are the symptoms during pregnancy?

Women with group B streptococcus often have no symptoms (in nearly half of cases)[2]. Sometimes there may be clinical signs such as a burning sensation in the vagina.

Outside of pregnancy, group B streptococcus can sometimes also be responsible for mild infections that are easily treated with standard antibiotics.

This bacterium often causes no problems for the mother; however, if it goes on to infect the newborn, rare but serious complications may develop.

Who carries it?

In pregnant women, carriage rates vary, but it is estimated that: approximately 10 to 30% are carriers[3]; in France, this represents 10%, or at least 75,000 per year[4].

Of these, approximately 40 to 70% transmit the bacteria to their baby during labour, and 1 in 2,000 newborns will develop an infection[5].

It is not yet known why some women become carriers and others do not. This may be due to a genetic predisposition and/or an imbalance in the microbiome, as we shall see below.

A positive Group B Streptococcus test result is not a contraindication to breastfeeding.

For the newborn: 

"Group B streptococcus is the leading cause of neonatal infection," notes Professor Claire Poyart, Head of the Bacteriology Department at Cochin Hospital (APHP) and Director of the National Reference Centre for Streptococci. It can cause miscarriages as well as premature births [6].

According to one study, 57,000 miscarriages worldwide per year are attributable to the bacterium [7]. It is also thought to be responsible for 3.5 million premature births [7].  

In the event of infection, the newborn may develop a severe illness. This most commonly manifests as septicaemia (a systemic infection of the body) and respiratory distress (the inability of the lungs to function properly). Sometimes these symptoms are accompanied by inflammation of the membranes surrounding the brain (meningitis). It can be responsible for the death or disability of infants.

The child may be infected at birth or later, generally around 3 weeks after delivery. Approximately 300,000 children are affected worldwide each year [8]. In France, 500 cases of invasive neonatal infections associated with group B streptococcus are recorded every year. These cause between 50 and 100 deaths [9].

For the mother: 

For the mother after delivery, the infection can cause a urinary tract infection, endometritis (infection of the inner lining of the uterus), septicaemia, or chorioamnionitis (infection of the placental tissues and amniotic fluid).

Lorsque la mère est infectée, certains facteurs augmentent la probabilité que l’infection se transmette à l’enfant, notamment :
- Déclenchement accouchement ou rupture des membranes avant 37 S de grossesse
- Rupture des membranes lorsque le travail commence à la date prévue et qu’il est probable qu’il dure plus de 18 heures
- Fièvre légère inexplicable durant le travail
- Antécédents de naissance où le streptocoque B a été transmis au bébé
- Présence de SGB dans l’urine ou infection de la vessie causée par le SGB.

Les premiers signes d’infection au streptocoque B par le nouveau-né sont : 
- fièvre
- irritabilité
- léthargie
- difficultés respiratoires
- teinte bleutée de la peau
 - difficulté à s'alimenter.

The Haute Autorité de Santé recommends that expectant mothers undergo routine screening for Group B Streptococcus carriage during pregnancy, between weeks 34 and 37. This vaginal swab is most commonly taken during the last gynaecological check-up. It should also be carried out in cases of premature labour or premature rupture of membranes.

The test is simple and painless; it involves taking a swab from the vagina and rectum using a cotton bud. The swab is then cultured to check for the presence of GBS.
 

Even if you are planning a caesarean, you should still have a screening test in case your waters break or labour begins before the scheduled date.

If you have or show any of the symptoms mentioned above, you will receive intravenous antibiotics during labour or if your waters break before term. This strategy significantly reduces infections at birth. Oral antibiotics and antibiotics taken before delivery have been shown to be ineffective in preventing the transmission of group B streptococcus. They must be taken during labour; otherwise there is a risk of the bacteria returning.

The HAS recommends antibiotic treatment in the following cases: 
- In the event of a diagnosis of GBS carriage during pregnancy, whether close to or distant from delivery;
- In the event of GBS bacteriuria during pregnancy;
- In the event of a history of neonatal GBS infection;
- In the absence of a vaginal swab screening for GBS, if 1 of the following risk factors is present: delivery occurs before 37 weeks of gestation, the duration of membrane rupture exceeds 12 hours, or the maternal temperature exceeds 38°C during labour. 
- If you have a history of maternal-foetal GBS infection or presented GBS bacteriuria during pregnancy, antibiotic treatment will be mandatory. 
 

If the bacterium is detected at birth in the newborn, an antibiotic is also administered to the infant intravenously during the first 48 hours of life.
However, the infection may develop within 7 days of birth, or even later. And in those cases, treatments are less well established.
Vaccines against group B streptococcus are under investigation, but no real prospects yet…

There are risk factors we cannot act upon — for example, age and underlying conditions such as diabetes or cancer are potential risk factors.

We can try to reduce the risk of infection by looking after our microbiome. These approaches are inexpensive and easy to implement.

Au-delà des risques pour vous et pour votre enfant, si vous êtes testée positive, vous allez recevoir un traitement antibiotique durant votre travail. 

Le microbiote se constitue lors de la naissance par un phénomène appelé colonisation bactérienne. Lors d’un accouchement par voie basse, le bébé passe par la muqueuse vaginale, colonisée par des milliards de bactéries. Ainsi, cette exposition agit comme un “premier vaccin”, lui permettant de développer son immunité.

Les études ont montré que le mode d’accouchement avait un impact décisif dans le microbiote du bébé. Les enfants nées par voie basse à la maison, et exclusivement allaités, ont un plus grand nombre de bactéries “bénéfiques” [14]. Les différences les plus notables se voient pour les bacteroides, qui auraient une influence positive sur le système immunitaire et seraient considérées comme pouvant aider à résorber les inflammations [15].

Pour en savoir plus, allez voir notre article sur le microbiome du nourrisson.

Quand on prend un traitement antibiotique, toutes les bactéries sont tuées, y compris les bonnes. Une étude[16] sur des mamans ayant reçu des antibiotiques suite à une infection à SGB a montré que les bébés avaient un microbiote différent (moins de bacteroides bénéfiques, beaucoup trop de enterococcus and clostridium), et que ces différences persistaient encore plus si le bébé était né par césarienne. Mais la bonne nouvelle c’est que l’allaitement semblait corriger une partie de ces effets (moins de clostridium, plus de lactobacillus) !

J’ai été testée positive, est-ce que je peux faire quelque chose ?
Vous pouvez essayer de suivre ces conseils pendant au moins 2 semaines, et demander de vous faire re tester, si c’est possible. L’idée est de développer les bonnes bactéries, et de booster son système immunitaire. Au mieux vous aurez réduit les risques de contamination du bébé en cas d’examen vaginaux, de décollement des membranes, et en général durant le travail !