Group B Steptococcus Screening

Group B Strep (GBS) is a bacteria that about 30% of women have living in the vagina. It can cause a symptomatic infection for a woman, sometimes causing a UTI, or it can cause an infection postpartum in the uterus. But very often it is completely asymptomatic and is simply part of the bacterial flora of the vagina. We recommend screening for the presence of GBS when you are pregnant (between 35-37 weeks) because having this bacteria present in the vagina or rectal area is a major risk factor for the development of a GBS infection in the infant. GBS infection of the infant can be quite serious and even fatal. Knowing if you are colonized with this bacteria allows us to reduce the risk of the infant developing an infection with this bacteria during delivery by giving the mother antibiotics (usually penicillin) while in labour. If you know you are positive for GBS, it is important to come to hospital if there are signs of labour and especially if your water breaks, so that antibiotics can be given before the baby is delivered.

The risk of a baby having a bad infection with GBS after delivery is small, but the consequences can be very significant. Before screening and treatment became common, the odds of this type of infection was about 2 per 1000 babies. Of those babies who develop an infection there is a 2-3% risk of death, although this is higher in babies born preterm, and higher depending on the location of the infection. Babies who survive the infection may be left with permanent disabilities such as blindness, deafness, seizures, and cognitive impairments.

After the source of the infection was discovered and screening and treatment became routine, the odds of this type of infection in babies has been reduced to about 0.25 per 1000 babies. Some of the infections that still happen occur because screening and/or treatment was declined. Some of them occur because labour happens so quickly that treatment isn’t possible.

We recommend that every woman be screened for GBS. Colonization with this bacteria can change so we recommend screening in each pregnancy, closer to the end of pregnancy. Someone who is negative in one pregnancy might still be positive in another pregnancy.

If you decide that you do not want to be screened for GBS, treatment to prevent infection in the baby can be initiated based on risk factors. The following risk factors increase the risk of the baby having infection with GBS and in these settings we would definitely recommend treatment with antibiotics:

Delivery at less than 37 weeks of gestation (and no negative GBS swab available)
Rupture of membranes for 18 or more hours before delivery
Chorioamnionitis (an infection in the fluid and membranes around the baby)
GBS detected in the urine during the pregnancy
Temperature ≥38ºC during labor
Prior delivery of an infant with GBS infection
The antibiotic most often used is penicillin. If you are allergic to penicillin there are other options. Penicillin has been around for a long time and has been used very often in pregnancy with no adverse effects noted for the infant.

If for some reason you were not screened for GBS (i.e if you delivered early before screening was done, or if you decided not to be screened), or if you were positive for GBS but did not receive adequate antibiotics in labour (i.e the labour happened so quickly that it couldn’t be done), then we will monitor the baby’s condition after delivery carefully. If there are any signs of infection either in the hospital or after you go home with your baby, you should seek care for your baby immediately.

For women having elective c-sections (scheduled prior to labour) the risk of GBS infection of the newborn is very small as the baby will not be coming down through the vaginal canal, and in most cases the sac around the baby will be intact until just before the baby is delivered. There is always a possibility that you may go into labour or your water may break prior to your scheduled c-section, but this is a minority of patients and in these situations we typically give an antibiotic and proceed with the c-section, thereby reducing the risk. Screening for GBS in women having a repeat c-section can be done, but many elect not to do this.