What is Group B Streptococcus and Pregnancy?
Group B Streptococcus (GBS) is a type of bacteria that usually lives in your gut and urinary tract. In the United States, it’s the leading cause of severe infections in newborn babies, which can lead to serious illness or even death. GBS can cause infections in newborns in two ways – either within the first week of life (early onset) or after the first week (late onset). However, current treatments are only effective at preventing the early onset type.
The rest of this article will discuss the latest advice on how doctors screen pregnant women for GBS during prenatal check-ups. It will also talk about the measures taken during childbirth to prevent early onset GBS infection in the baby.
What Causes Group B Streptococcus and Pregnancy?
The key factor increasing the chance for a newborn to have an early-onset Group B Streptococcus (GBS) infection is if the mother carries the GBS bacteria in her genital tract during labor. The GBS bacteria normally live in the digestive tract and can move to the genital area, which is how mothers can carry the bacteria during childbirth. It’s important to test for GBS in each pregnancy, as the bacteria can come and go.
If a pregnant woman has GBS in her urinary tract at any time during the pregnancy, it indicates a large presence of the bacteria and she should get treatment to prevent infection in the baby, even if a GBS test later in pregnancy comes out negative.
Young maternal age and being of black ethnicity are also factors that can increase the risk of a newborn contracting an early-onset GBS infection. If a mother gives birth prematurely (before 37 weeks), has a fever during labor (over 100.4 F or 36 C), or if her waters break and it takes a long time for labor to start (over 18 hours), these are all things that can increase the risk.
GBS bacteria are found in 10-30% of pregnant women. Without taking preventive steps, a newborn has a 1-2% chance of getting an early-onset GBS infection if their mother carries the bacteria.
Risk Factors and Frequency for Group B Streptococcus and Pregnancy
Group B Streptococcus (GBS) colonization affects 10-30% of pregnancies. Over the past two decades, measures like screening, use of medicine during childbirth (intrapartum prophylaxis), and efforts to prevent early-onset GBS disease have significantly reduced the frequency of early-onset GBS infection. Earlier, in the 1990s, about 1.7 out of 1000 newborns had this infection, but now it’s down to 0.34 to 0.37 out of 1000 births. It’s important to note that 70% of these instances occur in full-term babies (those born after 37 weeks).
Interestingly, 60% of early-onset infections are in patients who tested negative for GBS in the rectovaginal area between weeks 35 to 37 of pregnancy. This is because GBS colonization in the rectovaginal area is not continuous. From those who test positive for GBS between 35-37 weeks, up to 33% aren’t colonized at delivery. But about 10% of women who are colonized at delivery might have a negative test result between weeks 35-37 of their pregnancy.
Testing for Group B Streptococcus and Pregnancy
The main way to defend against early-onset GBS (Group B Streptococcus) infection is to give antibiotics to the mother during childbirth. Recognizing which mothers need these antibiotics during labor is a crucial part of pregnancy check-ups. The Center for Disease Control and Prevention recommends a universal culture-based screening for all pregnant women.
The healthcare professionals who take care of pregnant women should perform a test (called a rectovaginal culture) for GBS for all their patients between weeks 35 and 37 of their pregnancy. The test is done during this stage of pregnancy because its results are 95-99% more reliable in the first five weeks after it’s collected.
Women who are planning a preterm or early term induction of labor may benefit from taking the GBS test at or before their 35th week of pregnancy, while first-time mothers with an unfavorable cervix may benefit from having the GBS test at 37 weeks. When the GBS test is performed, the medical team should also do antibiotic susceptibility testing – this helps them decide what type of antibiotic to give patients who are allergic to penicillin.
Having GBS bacteria in your urine is another sign that the bacteria are present in your genital area. All pregnant women should be screened for asymptomatic (i.e., without symptoms) bacteriuria (i.e., bacteria in the urine) during pregnancy. All women who have GBS bacteria in their urine at any point during pregnancy should get antibiotics during labor.
In cases where the GBS status is unknown, antibiotics should be started in patients with preterm labor (less than 37 weeks into pregnancy), a fever during labor (greater than 100.4 F or 38 C), if the membranes have ruptured for more than 18 hours, and/or in patients who have previously had a child with invasive early-onset GBS infection.
Treatment Options for Group B Streptococcus and Pregnancy
Doctors typically use an antibiotic called penicillin G to protect against a bacterium known as Group B Streptococcus during childbirth. This antibiotic is given through an IV, or a small tube in your vein, during labor. When penicillin G isn’t around, doctors could use another antibiotic called ampicillin instead. They’ll do the same – give it through an IV during labor.
However, if someone is allergic to penicillin, they should not receive penicillin G or ampicillin. What happens then? Well, if a person has had a strong allergic reaction (like trouble breathing or hives) to penicillin or a similar antibiotic called cephalosporin, the doctor must know what the Group B Streptococcus is sensitive to to choose an alternative antibiotic. One such choice could be an antibiotic known as clindamycin. But, in some cases, the infection might appear sensitive to clindamycin but resistant to another antibiotic, erythromycin. Oddly enough, being resistant to erythromycin might cause resistance to clindamycin too. So, doctors would recommend another antibiotic, vancomycin, in this scenario.
If a patient with a penicillin allergy hasn’t had the susceptibility test, then vancomycin is still recommended. But it’s worth noting that there have been reports of resistance to antibiotics like fluoroquinolones, macrolides and vancomycin. For patients who’ve had a milder reaction to penicillin or cephalosporin, like a rash, another antibiotic called cefazolin might be used.
The key here is that the antibiotic treatment should start at least 4 hours before delivery to effectively prevent the transmission of Group B Streptococcus to the baby. That said, even if delivery is expected to happen in less than 4 hours, doctors will still start this treatment. Finally, it’s also worth noting that even though vaccines for Group B Streptococcus infection seem promising, there are currently no approved vaccines available.
What else can Group B Streptococcus and Pregnancy be?
Several medical conditions can share similar symptoms and may be confused with each other. These include:
- Bacterial pneumonia: a type of lung infection
- Cellulitis: a skin infection
- Urinary tract infection in women
- Dermatologic manifestations of necrotizing fasciitis: skin symptoms of a severe infection that damages tissues under the skin
- Diskitis: inflammation of the intervertebral disk space
- Endometritis: inflammation of the lining of the uterus
- Epidural abscess: a collection of pus between the outer covering of the brain and spinal cord and the bones of the skull or spine
- Infective endocarditis: an infection of the inner lining of the heart chambers and valves
- Meningitis: an inflammation of the protective membranes covering the brain and spinal cord
- Osteomyelitis in emergency medicine: infection of the bone, often requiring emergency treatment
- Septic arthritis: joint infection
- Urinary tract infection in pregnancy
- Wound infection: when a wound becomes infected with bacteria
What to expect with Group B Streptococcus and Pregnancy
Since the start of widespread screening for GBS (Group B Streptococcus) – a type of bacterial infection – and the use of antibiotics during labour, the occurrence of GBS infections in newborns has dropped by around 80%. The effectiveness of using antibiotics during labour is estimated to be between 86% to 89%. However, prenatal screening may not identify all women carrying GBS at the time of labour, because their bodies may be temporarily harbouring the bacteria. About 60% of GBS infections in newborns happen in babies whose mothers tested negative for GBS between the 35th and 37th weeks of pregnancy.
GBS infections in newborns usually show up in the first 24 to 48 hours after birth with symptoms like breathing difficulties, and brief pauses in breathing that can suggest blood infection. These infections often result in severe blood infection and pneumonia, but can occasionally cause meningitis. Death from GBS infection is much more common in premature babies than full-term babies. In fact, premature babies with GBS infections have a 20% to 30% chance of fatalities, as compared to just 2% to 3% in full-term babies.
Possible Complications When Diagnosed with Group B Streptococcus and Pregnancy
When a mother-to-be is infected with group B streptococcus (GBS), it can lead to several negative outcomes. These may include an increased rate of fever-related health issues and a particular kind of infection in the membrane around the fetus, which can lead to serious illness in the mother. In addition to this, maternal GBS can also result in inflammation of the uterus, the need for a cesarean birth, infections in surgical wounds post-delivery, kidney infections, and other infections that climb from lower to higher regions in the body – possibly causing serious illness in the mother and premature birth. Group B streptococcus can also cause breast inflammation and abscesses. Finally, although they are uncommon, illnesses like meningitis, heart valve infection, and bone infection have been noted as complications.
Common Consequences:
- Fever-related illnesses
- Infections in the fetal membrane
- Inflammation of the uterus
- Need for cesarean birth
- Post-delivery surgical wound infections
- Kidney infections
- Ascending infections that can lead to serious maternal illness and premature birth
- Breast inflammation and abscesses
- Rarely, illnesses like meningitis, heart valve infection, and bone infection
