GBS test in pregnancy – test for group B streptococci [EXPLAINED]

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The GBS test is a microbiological screening test for group B streptococci (GBS is derived from their English name for Group B Streptococcus). It should be performed in pregnant women to determine the risk of transmission of infection to the baby during childbirth. Infecting a newborn baby with a bacterium can cause a life-threatening condition. How is GBS screened during pregnancy? Is it painful? What are the risks of carrying GBS for mother and child?

What are group B streptococci?

GBS streptococci, represented by bacteria of the species Streptococcus agalactiae are part of the natural human physiological flora. They live in the digestive and urinary tract, which are the likely source of vaginal colonization. According to estimated estimates, about 30 percent. women in Poland are GBS carriers, settled in the vagina, rectum or both.

Read: What streptococcal infections can occur

GBS test – when should it be performed?

Every pregnant woman should undergo GBS examination not earlier than between 35 and 37 weeks of pregnancy. Specialist diagnostics is necessary because streptococcal infection does not give any characteristic symptoms.

What does the GBS test look like?

Taking the material for testing is a fairly simple and short procedure that is used for a special, thin swab. Among pregnant women, this test is commonly said: GBS smear, GBS culture, GBS culture. A sample for group B streptococcus is taken from the lower part of the vagina (vestibule) and the rectum.

The sample can be collected by the pregnant woman (after carefully reading the instructions), by the doctor or midwife. The speculum should not be used during the examination. After the sample is taken, it is sent to a microbiological laboratory. The waiting time for the result is about 5 days. Importantly, the pregnant woman should take the result with her to the hospital and present it before the birth.

See also: What is an ASO examination?

GBS in pregnancy – threats to the pregnant woman

GBS during pregnancy may be asymptomatic, the woman does not even know that she is its carrier. She only finds out about a positive result when she is tested for GBS during pregnancy.

As a result, both in pregnancy and in the postpartum period, urinary tract infection, inflammation of the membranes can occur, endometritis, sepsis and, rarely, meningitis. It is extremely rare for a woman to die from pregnancy-related GBS infection.

Also read: What is urosepsa

GBS – newborn colonization

GBS is colonizing the newborn’s oral cavity, followed by the respiratory tract and digestive tract following vertical transmission during labor from the mother from her vaginal microflora and the cervical canal. The risk of neonatal infection is approximately 70%and the incidence is 2 to 4 in 1000 liveborn babies. Infection with streptococcus causes the so-called early onset of infection in the first week of life, usually in the form of respiratory disease including pneumonia and sepsis.

Read: Aspiration pneumonia in a child

GBS – what can it cause in a newborn?

Development may occur in an infected newborn severe invasive disease. In most cases, the infection develops in the first week of life – then it is called an early one sepsis. The late form of the disease appears after the first week of a child’s life. In general, the disease may develop until a child is 3 months old. Infants with invasive disease usually develop sepsis or pneumonia, and may develop (but in rare cases) meningitis, purulent arthritis, and osteomyelitis.

GBS – perinatal antibiotic prophylaxis

If GBS is confirmed, the gynecologist conducting the pregnancy must record this information in the pregnant pregnancy card. The information on the susceptibility test result should also be included there. According to the recommendations of the Polish Gynecological Society, infection prophylaxis Streptococcus agalactiae first of all, it should be implemented in relation to:

1. women in whom at week 35-37 presence detected S. agalactiae,
2. women who have a negative microbiological test result but have a history of a perinatal infection S. agalactiae, with one of the previous children,
3. women with a negative microbiological test result, but earlier in the current pregnancy presence found S. agalactiae in urine
4. women who have started labor before scheduled carrier testing was performed S. agalactiae (before 35-37 weeks),
5. women with unknown carrier test results, but who came to the hospital 18 hours after the rupture of the membranes,
6. women with unknown carrier test results but with body temperature ≥38°C.

Prophylaxis should begin immediately after admission to hospital. The recommended drug is penicillin G administered intravenously in the first dose of 5 million units, and then 2,5 million units every 4 hours until delivery. It is possible to use ampicillin in the first intravenous dose of 2 g and then 1 g every 4 hours intravenously until delivery.

Read: Water oozing – what could it mean?

GBS – management of newborns

The recommendations of the Polish Gynecological Society indicate that if the child’s mother was treated with perinatal antibiotic prophylaxis in connection with GBS, the child should be under observation for at least 24 hours. When any signs of infection appear, they must undergo full GBS diagnostics. The material for research is taken from the newborn’s ear and navel.

In newborns older than 34 weeks of pregnancy, who had no symptoms, and the mother received perinatal prophylaxis at least 4 hours before the birth of the child, the child should be monitored in the ward for a period of 24-48 hours without performing additional tests to exclude GBS infection. If no undesirable symptoms appear during this period, the child may be sent home.

In newborns older than 34 weeks of pregnancy, without clinical symptoms of infection, whose mothers received perinatal prophylaxis less than 4 hours before the birth of the child (if there are no clinical symptoms of infection), the child should be monitored for a period of 24-48 hours and it is recommended performing a CRP concentration test in the blood serum – 2-3 times every 12h. It is not necessary to perform a microbiological blood test. If the test results are normal and there are no symptoms, the baby may be released from the hospital.

In newborns younger than 34 weeks gestation, regardless of maternal intrapartum prophylaxis, if there are no clinical symptoms of infection, the child should be monitored for 24-48 hours and it is recommended to test the concentration of CRP in the blood serum – 2-3 times every 12 hours . If the newborn has symptoms of respiratory failure – respiratory distress syndrome (ZZO) – microbiological blood tests should be performed and antibiotic therapy should be started.

All newborns born to mothers diagnosed with:

1. fever> 38 ° C in the mother and the presence of one of the symptoms: uterine tenderness, fetal tachycardia, presence of “fetid” amniotic waters, premature rupture of the membranes (> 18h), leukocytosis in the mother,
2. premature rupture of the membranes and GBS colonization regardless of the clinical symptoms of infection,

require a complete set of tests to be performed in order confirmation or exclusion of sepsis and infection of the central nervous system and starting antibiotic therapy.

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