GBS in pregnancy

What are Group B streptococci and how often do they occur?

Group B Streptococcus (GBS) also known as Streptococcus agalactiae is one of many bacterial species that live in the human body. They are majorly found in the intestines but can migrate to the vaginal region where they can potentially cause sepsis in newborn infants (CDC, 2010). Approximately one in four women are carriers of these streptococci. The prevalence is highest in the United States (26%) and lowest in India and Pakistan (12%), 19% in Asia, 22% in the Middle East, 19% in North Africa and sub-Saharan Africa, 14% in Central and South America (Gilbert, 2003).

Morbidity of GBS
Approximately one in four of all pregnant women have group B streptococci in their vagina and hence are carriers. Normally these bacteria are relatively harmless and most babies of mothers who carry group B streptococci are born completely healthy (Gilbert, 2003). Fortunately, it happens very rarely that the bacteria cause a serious disease in babies (about 1 in 200) and leads to the death of the baby.

According to the CDC 2010, GBS infections remains the leading cause of infant mortality (i.e. Infant death) due to infectious causes in the United States of America (CDC, 2010). Group B Streptococci causes sepsis in the infant which can lead to septicemia, pneumonia, or meningitis and death if not well treated. In the 1970s initial case reports had a fatality rate of 50% in infants affected by GBS (CDC, 2010) though this has dropped to 4.7% in 1993-1998 (Gilbert, 2003). In the 1980s studies and clinical trials showed that administering antibiotics to pregnant women intravenously during labor reduces the risk of infants getting early onset infection of GBS from 1 in 200 to 1 in 4000 this method of prevention is called intrapartum antibiotic prophylaxis (CDC, 2010). In 1996 and 1997, Intrapartum antibiotic prophylaxis was recommended by the American College of Obstetricians and Gynecologists (ACOG), Center for Disease Control (CDC) and American Academy of Paediatrics (AAP). In 2002 guidelines for prevention of early-onset GBS recommended the universal culture-based screening of all pregnant women for GBS in the 35th to 37th week of pregnancy in order to optimally identify the women who need intrapartum antibiotic prophylaxis (CDC, 2010). All these factors have greatly contributed to the reduction of the disease incidence of early onset GBS from 2–3 per 1000 live births in the 1970s to 1.4–1.8 per 1000 live births in 1990. Universal Culture-based screening and Intrapartum antibiotic prophylaxis led to the further decline of GBS incidences to 0.2 – 0.5 cases per 1000 live births during the mid-1990s. However, the incidence of late-onset GBS remains the same at 0.4/1000 births (Gilbert, 2003).

Newborn GBS infection risk

Newborn GBS infection risk

 

 

Types of Group B streptococci infection

There are two types of GBS infection in infants. They are the early onset and the late onset Group B Staphylococcus infections.

The Early-onset GBS infection:
This occurs when the infant comes down with sepsis as a result of Group B Streptococcus infection within a week of delivery. The incidence of this infection has reduced dramatically from approximately 1.7 cases per 1000 births in 1990 to 0.34 – 0.37 cases per 1000 births over by 2005. However, it still has a higher mortality rate that the late onset GBS. This is due to GBS screening in all pregnant women coupled with intrapartum antibiotic prophylaxis. Symptoms usually include respiratory distress and difficulty in breathing (apnea) over the first 24 to 48 hours. More commonly pneumonia and sepsis are seen within the first week of life of the neonate and less commonly meningitis can be observed (CDC, 2010).

Late-onset GBS infection
This occurs after 1 week of delivery. The fatality rate is markedly lower than that of the early onset (i.e. lesser babies die from late onset GBS than from early onset). However, prevention measures taken for GBS has not been successful in reducing the rate of late-onset GBS over the years.

What are the risk factors of GBS in babies?

  • There are a number of factors that tell you something about the probability. The Risk of infection increases if you are a carrier and:
  • If you have preterm labor (before pregnancy week 37 )
  • If your amniotic membrane ruptures with a delay of up to 18 hours or more at birth (increases possibility of intra-amniotic infection)
  • If in your current pregnancy, group B streptococci are detected in the urine or in the vagina
  • The inoculum size i.e. the amount of Group B Streptococci present in the vagina
  • You have a child that had a streptococcal infection at birth
  • The prevalence is also higher in African Americans (CDC, 2010).

How do I know if I am a carrier of group B streptococci?

If you are a carrier of group B streptococci, you probably will not know. Normally the bacteria are completely harmless and do not make you sick.
Therefore, if you want to know if you have group B streptococcus, you should ask your doctor for a test. This is not done routinely unless you belong to a risk group. Also, a laboratory test can be done in the last few weeks (35th to 37th week) before labor.

There are two ways to know if you are a carrier of Group B Streptococci. They are the risk-based approach and the culture-based approach. In the risk-based approach, pregnant women are screened based on risk factors mentioned above and in the CDC guidelines. If you fall into any of the categories you are likely to be given intrapartum antibiotic prophylaxis during delivery. Another method is the culture-based approach in which samples from the vagina and intestine are taken using sterile swabs (Q-tip) and sent to the laboratory for analysis using different kinds of culture media (CDC, 2010).

However, according to the CDC, multiple studies have pointed to evidence that culture-based screenings are better than risk-based screening in reducing the incidence of early-onset GBS in neonates (CDC, 2010).

I am a carrier of group B Streptococcus. What now?

If you have ever had an ‘infected group B streptococci child or if culture screening from your vaginal samples detects the presence of group B Streptococci, then you are a carrier. This way the doctors will know what to do during childbirth. Prevention of early onset Group B streptococcus is by intrapartum antibiotic prophylaxis at birth or as soon as possible after the rupture of the amniotic membrane. The antibiotic is usually given intravenously. The antibiotics used is either Penicillin or Ampicillin given four hours before delivery of the baby. The baby is immediately examined for any infection after birth (CDC, 2010).

A discussion with an obstetrician / gynecologist to help develop a birth plan to protect your child from infection is needed. In most cases, the doctors manage to bring your baby safely, healthy and free from infections to the world.

What do I need to know about my group B streptococcus?

Most babies who come into contact with group B streptococci before or during birth remain completely healthy and are doing well. Though they may end up being carriers of the bacteria.

But unfortunately, about 1 in 200 babies develops Group B Streptococcal infection immediately after birth. Fortunately, due to GBS screening during pregnancy and intravenous intrapartum antibiotic prophylaxis babies rarely come down with the infection and fatality rate of the early onset GBS has declined. 

The greatest risk of infection is during birth. A caesarean section is not so useful but can be done before labor or rupture of the amniotic sac.  This is because though the caesarean section itself poses very little risk of infection to the baby but Group B streptococci are capable of passing through the intact amniotic membrane from the vagina and thereby infecting the fetus. The data on the risk of transmission in preterm neonates delivered using caesarean section is limited (CDC, 2010).

Decide your doctor / health care professional but only during birth that you need a so-called emergency C-section, then the bacteria can be transmitted to your baby despite the caesarean you. Therefore, you will get antibiotics and your baby will be examined for streptococci.

How can I protect my child from infection at birth?

If you do not belong to any of the above risk groups, then it is very unlikely that your baby will develop a streptococcal infection. 

If you belong to the risk group, the antibiotics such as Penicillin and Ampicillin administered intravenously will prevent infection. Ideally, the treatment begins four hours before your baby is born or immediately the amniotic membrane breaks open (CDC, 2010).

A pediatrician decides immediately after birth whether your child needs further help:

  • If you have been treated during birth and you and your baby are healthy, no further antibiotics are given
  • If you have not been treated during birth, but you and your baby are perfectly healthy, your baby will be monitored for 48 hours and possibly a laboratory test will be conducted.

If you and / or your child have first signs of infection, your baby will be immediately treated with antibiotics (intravenously)

Other methods of prevention of early onset Group B streptococcus that have been investigated include intramuscular intrapartum antibiotic prophylaxis, douching of the vagina with chlorhexidine and use of antibiotics (oral or intramuscularly) during pregnancy. However, all these methods were ineffective. There is currently no licensed vaccine for Group B streptococci infections.

Symptoms of group B streptococcal infection?
Infections with group B streptococci are usually seen within one week after birth. 90 percent of which occur within the first 24 hours.

Typically, symptoms will be seen by the doctor immediately after birth or after a short time. Symptoms to be watched out for include:

  • Lethargy
  • Irritability
  • Low blood pressure
  • Have an unusually high or low temperature
  • or an unusual cardiac and/or respiratory rate show (apnea)

Infection with late onset group B streptococci occurring in the second week of life can also be noticed. Less common are infections occurring within a month and very rarely can infections with Group B streptococcus occur, once your baby is three months old  

Group B streptococci can cause bacterial meningitis but more commonly they cause septicemia and pneumonia (CDC, 2010). The later the infection occurs, the less problematic are the infections. Most babies respond well to treatment, but meningitis can also cause permanent health problems
Talk to your doctor or midwife if you are concerned or notice any of the symptoms of an infection with your baby. Even if it is just a false alarm.

Conclusion.

The importance of Group B streptococcus screening in pregnancy can be seen in the fact that Group B streptococcus also known as Streptococcus agalactiae is the leading cause of infectious neonatal death in the United States of America. The use of intravenous intrapartum antibiotic prophylaxis and Group B Streptococcus screening during pregnancy has helped significantly reduced the mortality rate from 50% (i.e. 1 in every 2 babies infected with early onset Group B streptococcus infection) in 1970 (CDC, 2010) to 4.7% in 2005 (Gilbert, 2003). This shows the marked importance of GBS screening coupled with intravenous intrapartum antibiotic prophylaxis in improving the prognosis of babies of mothers who are found to be carriers of group B Staphylococci.

References

  1. CDC. (2010). Prevention of perinatal Group B Streptococcal disease: Revised guidelines from CDC 2010. 1600, Clifton Road, N.E., MS C-23,
  2. Atlanta, GA 30333: Jennifer R. Verani, MD, National center for immunization and respiratory disease, CDC.
  3. Gilbert, R. (2003). Prenatal screening for group B streptococcal infection: Gaps in the evidence. International Journal of Epidemiology, 2–8.
  4. Main EK, Slagle T. Prevention of early-onset invasive neonatal group B streptococcal disease in a private hospital setting: the superiority of culture-based protocols. Am J Obstet Gynecol 2000;182:1344–54
  5. Schrag S, Gorwitz R, Fultz-Butts K, Schuchat A. Prevention of perinatal group B streptococcal disease.       Revised guidelines from CDC. MMWR
  6. Recomm Rep 2002;51:1 – 22  
  7. Davies HD, Adair CE, Schuchat A, Low DE, Sauve RS, McGeer A.Physicians’ prevention practices and incidence of neonatal group B streptococcal disease in 2 Canadian regions. Can Med Assoc J 2001;164:479 – 85
Article researched for: Private Doctors Clinic in Manchester Eccles

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