Group B Strep

What is Group B Strep?

Group B streptococcus (S. agalactiae) is a bacterium that can be found to colonize in the rectum and/or vagina in about 30% of all women. Colonization can be transient, chronic, or intermittent. Genital colonization does not usually produce any symptoms, although Group B Strep can be the cause of some urinary tract and postpartum infections.

We can screen for Group B Strep (GBS) by swabbing the entrance of the vagina and the perineum.  The sample is sent to a lab to be cultured for the presence of GBS. The culture is done at 36 weeks. We will also submit a urine culture if the vaginal culture is positive. The presence of GBS in the urine indicates a higher risk for neonatal GBS disease.

Group B Strep can be transmitted to your baby during birth. When babies are colonized with GBS, they can develop GBS disease. Overall, the incidence of early-onset, invasive neonatal GBS disease is about 1% when no treatment is undertaken to prevent transmission. This is considered a significant risk. Increased risk factors or infection include: preterm birth, rupture of membranes >18 hours, heavy colonization of GBS, maternal fever of 100.4°F, maternal GBS UTI.

Antibiotics are not prescribed prenatally for asymptomatic GBS because colonization can recur before term, and prenatal treatment has not been shown to prevent neonatal infection.

Early-onset Group B Strep infection in newborns occurs during the first week (most commonly within the first 2 days, 90% of infections manifest within 24 hours). Most babies who get sick (80%) are preterm or of low birth weight and have secondary risk factors of infection. Signs of infection include respiratory distress, temperature instability, lethargy, poor feeding, pallor, tachycardia, abdominal distension, jaundice, and rarely, meningitis. Babies who become sick will need to be treated by a physician in the hospital.

Late-onset GBS infection occurs when the baby is over a week old and usually manifests as meningitis. Infection may also present as infection in the eyes, sinuses, joints, bones, skin, ears or lungs. Because some of these infections may not actually be a result of transmission at the time of birth, but contact with GBS at a later time- it is important for GBS positive mothers to practice good hygiene and hand washing routines.

The Centers for Disease Control (CDC) and the American College of Obstetricians and Gynecologists (ACOG) both recommend intravenous (IV) antibiotic therapy for GBS positive women during labor in order to prevent neonatal Group B Strep infection. The CDC reports an 80% reduction in the rate of neonatal GBS disease with the use of intravenous antibiotic therapy during labor. Intravenous antibiotic therapy does not guarantee that newborns will not be colonized with or develop an infection from GBS. The use of antibiotics carries its own risks- allergic symptoms, gastro-intestinal problems, secondary infections and anaphylaxis. If your vaginal culture is positive for GBS, we will do a urine culture. When urine cultures are positive for GBS, we recommend IV antibiotics in labor because it is the only proven treatment to prevent early-onset GBS disease in the newborn.

Other options for treatment include treating prenatally with nutritional supplements and utilizing a chlorhexadine lavage (using a peri-bottle with a diluted solution of 4% chlorhexadine and water to wash the vulva/perineum/rectum) during labor. These have not been proven to prevent early-onset GBS disease.

Prenatal Screening

Prenatal GBS screening at 35-37 weeks is routinely used in many midwifery practices to identify which babies may be at risk for GBS disease. However, it is important to note that women are frequently transient carriers of GBS. A woman who is GBS negative at 36 weeks may be positive by the time she delivers (and vice versa). Screening and treatment of GBS does not guarantee that your baby will not become colonized with GBS or develop GBS disease.

GBS screening is an option- you don’t have to do it. Here are some facts to consider:

  • The GBS screen is minimally invasive- you can obtain the sample yourself by swabbing the entrance of the vagina and the perineum (or your midwife can do it for you). The procedure is not painful.

  • Knowing your GBS status may be important if your baby becomes sick. The doctors will need to know in order to treat your baby quickly.

If your GBS screen is negative: Great! 92% of women whose culture is negative will remain negative at delivery. You may choose to add nutritional supplements to your diet to encourage healthy vaginal flora, just to reduce the chance of GBS colonization before delivery. Other treatments are not indicated or recommended.

If your GBS screen is positive: 84% of women whose culture is positive will remain positive at delivery. There is a chance that your GBS status will naturally change. You have options for treatment that your midwife will discuss with you.

No matter what your Group B Strep status is- or your choice of treatment if you are positive- your midwife is still watching your baby very closely in the hours after birth for any signs of GBS disease. You will be given detailed instructions for monitoring your baby’s health.

Please make note of the following:

You have the opportunity and responsibility to review the information on this form and ask questions, and to make your own decisions regarding your and your baby’s care.

Understand that if you refuse the GBS test, and you are actually GBS positive, there is a chance your baby could become sick with GBS disease. Understand that a negative result does not guarantee your baby will not become sick with GBS disease.

Understand that your midwives recommend IV antibiotics in labor when both the vaginal and urine cultures are positive for GBS, or if your waters (amniotic membranes) have been ruptured longer than 12 hours with a positive vaginal culture. The health and safety of your baby are our priority.

Understand that good hygiene and handwashing routines are important to reduce the risk of transmitting GBS to your baby.

Understand that, if your midwife recommends transfer of you or baby to the hospital in labor or immediately postpartum, the hospital will probably administer antibiotics to one or both of you. Babies who are transferred with an unknown GBS status may be subjected to invasive diagnostic testing.

Read this informative article from Evidenced Based Birth here

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