Streptococcus agalactiae, otherwise known as Group B Strep (GBS), is a bacteria that approximately 20-25% of pregnant women have in their vagina and rectum. Carrying this bacteria does not mean that you have a sexually transmitted infection (STI) or that your hygiene habits are poor. Put simply, GBS can be temporarily present in all women, but it only becomes significant when you are pregnant because of the potential issues it might cause for your baby during delivery.
GBS can be passed to a baby as he or she passes through the birth canal at the time of delivery. If GBS bacteria are found in the vagina or rectum (measured using a urine sample or rectal swab) and the mother-to-be does not receive antibiotics whilst in labour, there is a 5-50% chance of her baby also becoming infected with GBS. The risk of transmission is higher if the mother has certain risk factors, including having a fever during labour, or giving birth prematurely.
GBS in newborns can lead to infections of the lungs, bloodstream and the nervous system; all of which can have severe consequences. To decrease the numbers of newborns with these complications, all pregnant women are now routinely screened for GBS to see if they are positive.
This screening is usually done between weeks 35 and 37 of pregnancy via a simple swab of the vagina and rectum. In some cases a swab will not be taken, or will be taken at a different time. Urine samples are taken at the start of pregnancy and then throughout, particularly if there is a chance of urinary tract infection. If a female’s urine cultures test positive for GBS, (even if it is at the start of her pregnancy) it will be assumed that she is still a carrier of the infection when it comes to delivery and she will be treated preemptively with antibiotics during labour. Women who go into premature labour, or those whose waters break early, will need to be screened promptly, before the 35- or 37-week mark. Finally, women who are having a scheduled Caesarean (C-section) will not need antibiotic treatment during their delivery, but may still be screened during pregnancy in case they do deliver vaginally.
With the problems that GBS infections can cause in newborns, you may wonder if having a scheduled C-section is the best way to manage the risk. This is definitely not the case! A natural birth is still entirely possible and the treatment for GBS is simple and effective. Your doctor or midwife will order IV antibiotics to be given during labour to reduce the chance of transmission. The drug of choice is usually penicillin, but if you are allergic, an alternative will be used. The aim is to administer the antibiotics at least four hours before your baby is born.
The implementation of routine screening and use of antibiotics when needed has proved to be very successful. Since this approach has come into effect, the prevalence of GBS infection in newborns is now only 0.5 per 1,000 live births.
It is important to note that women colonised with GBS can occasionally have issues, too. Having a large amount of GBS present in your urine can cause symptoms similar to a urinary tract infection. Oral antibiotics can be used to treat the infection. Having GBS can also slightly increase your risk of developing uterine infections at the time of delivery or just after. To date, there is no good data that suggests that treating all GBS positive women before delivery, reduces the risk to the mother. There are some myths of alternative treatments (such as garlic and colloidal silver) for women who test positive, but there is no data to back up these practices, and they are not recommended.
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