What is gbs in pregnancy ?
Streptococcus B(GBS) and pregnancy: everything about screening for childbirth
At the end of pregnancy, screening takes place to find out if you are a carrier of streptococcus B in your vaginal flora. What is the purpose of this test? What are the risks associated with this bacteria for the baby? What procedure should you follow if you are a carrier? We tell you everything.
During pregnancy, a pregnant woman must be particularly vigilant about certain bacteria. This is particularly the case with group B streptococcus , which can cause complications in the fetus.
What is group B streptococcus, or Streptococcus agalactiae? How do you get this infection?
Group B Streptococcus, GBS or Streptococcus agalactiae , from its Latin name, is a bacterium found in some men and women, in the digestive tract or in the vagina. This germ is often present in the body without causing symptoms.
A bacteria sometimes present in the flora of the vagina
Streptococcus B is found in the vaginal flora of at least 15% of women, in an asymptomatic manner. The Pasteur Institute specifies that this bacteria is found in 5 to 40% of women during pregnancy , " depending on the bacteriological techniques used and the populations studied" . But if the fact that it colonizes the vagina is generally without consequence for the pregnant woman , the presence of this bacteria can lead to infection of the baby during childbirth. There is therefore a protocol in place to reduce the risk of transmission.
Why screen pregnant women for streptococcus B(GBS)?
Although it is generally harmless in the woman who carries it, this germ can however be transmitted from mother to child, most often during childbirth, when it passes through the vagina . Indeed, the baby can inhale or even ingest vaginal secretions during childbirth, specifies the Pasteur Institute. However, this infection is not without consequences for a newborn, due to its weak immune defenses.
This is why GBS screening is systematically carried out in France at the end of pregnancy, ideally between 34 and 38 weeks of amenorrhea , or between 32 and 36 weeks of pregnancy .
In a document on “good clinical practices”, published in 2001 and revised in 2006, the High Authority for Health (HAS) estimated that at least 75,000 women per year in France were carriers of Streptococcus B in their vaginal flora .
Given that the consequences are significant in the postpartum period and for the newborn (it is even a " public health problem", according to the High Authority of Health), and that prevention (i.e. the prescription of antibiotics during labor) reduces the risk of neonatal and maternal infection by more than three quarters, its screening at the end of pregnancy is entirely justified .
Vaginal swab screening: how do you know if you have contracted streptococcus B infection while pregnant?
Unlike a cervical smear , GBS screening is completely painless, since it involves taking a sample of vaginal flora using a cotton swab , after inserting a speculum.
The sample taken is then cultured in the laboratory to reveal the presence or absence of Streptococcus B (GBS).
Note that this screening is recommended even if a cesarean section is scheduled or planned, in the event that delivery occurs earlier than expected . In the event of premature labor or premature rupture of membranes , the GBS screening sample will be taken urgently, in order to avoid a streptococcus B infection in the unborn baby.
What are the risks for the baby and the mother? Is this infection dangerous?
Streptococcus B infection at birth can lead to serious complications in the newborn. The medical community generally distinguishes two types of neonatal GBS infections : early infections, which occur in 80% of cases during the first 24 hours of the baby's life, and late infections, which occur between the first week of life and the baby's third month.
Early infection with Streptococcus B in the newborn most often manifests itself as septicemia (or more precisely bacteremia: presence of the bacteria in the blood) and respiratory distress . While a late infection will rather cause inflammation of the meninges, in this case abacterial meningitis . High fever is the main symptom.
Finally, for the young mother, streptococcus can colonize the urinary tract, and thus cause a urinary tract infection (or cystitis ), or give rise to endometritis , that is to say an infection of the endometrium which lines the uterus. In the most serious cases (and the rarest, fortunately), GBS infection can cause septicemia if the bacteria passes into the blood, or chorioamnionitis at the very end of pregnancy (infection of the placental tissues and amniotic fluid ).
According to the Pasteur Institute, approximately 500 cases of invasive neonatal infections are recorded in France each year , resulting in between 30 and 60 deaths . Screening at the end of pregnancy, and the use of antibiotic treatment in the event of a positive sample, has reduced the number of infections and mortality among newborns.
Risk factors for transmitting streptococcus B to the baby
Note that there are risk factors for transmission of group B streptococcus to the baby during childbirth, namely:
early rupture of membranes;
labor lasting more than 18 hours;
fever during labor;
a history of maternal-fetal transmission of GBS;
the presence of GBS in the urine.
What treatments are available to prevent streptococcus B infection?
In pregnant women, systematic screening for streptococcus B is recommended between 34 and 38 weeks . If the result is positive, and therefore GBS is present in vaginal secretions, antibiotic treatment (ß-lactam, in other words penicillin or amoxicillin, or a macrolide in case of allergy) will be started at the time of delivery , or as soon as the waters break in the absence of contractions. This is called antibiotic prophylaxis, in other words preventive antibiotic treatment. Ideally, this treatment should be started at least 4 hours before the baby is born.
In addition to a positive Streptococcus B screening test result at the end of pregnancy, antibiotic treatment is prescribed in the following cases, even in the event of a negative test :
in case of history of GBS infection during a previous pregnancy;
in case of GBS detected in urine during pregnancy;
in case of GBS detected in the vaginal flora during pregnancy;
in case of premature birth (before 37 weeks, or 8 and a half months);
in case of unexplained fever during childbirth;
when the rupture of the water bag dates back more than 18 hours (in the event that labor has not yet been induced).
In newborns, treatment for Streptococcus B infection is based on intravenous administration of a beta-lactam antibiotic (amoxicillin) over 10 days to 3 weeks, depending on the symptoms and manifestations of the infection (meningitis, etc.).
Although it is rare for the bacteria to be transmitted to the baby, the baby will be closely monitored by the healthcare team, for early treatment in the event of symptoms of a GBS infection.
Note that no vaccine is currently available against Streptococcus B infections.
