In the third trimester, your provider will probably test you for Group B Strep, or GBS, as part of routine prenatal care. It is a common part of late pregnancy care, but it can raise questions, especially if your test comes back positive. Many patients worry that it means something is wrong or that they did something to cause it. The truth is much simpler. GBS is common; it is not a sexually transmitted infection, and it does not mean you are unclean. It is a type of bacteria that many healthy adults carry without symptoms.
In pregnancy, the main concern is that GBS can pass to the baby during labor and delivery. The good news is that testing is simple, treatment is straightforward, and prevention is highly effective.
At The Ob-Gyn Center, we focus on making sure you understand what the results mean and what to expect on delivery day, so you can feel prepared and confident.
What is Group B Strep?
GBS is a bacteria that can live in the gastrointestinal tract and sometimes in the vagina or rectum. Many people carry it without symptoms. It can come and go over time, which is why testing is done late in pregnancy rather than earlier.
Being GBS positive does not mean you have an infection. It usually means you are colonized with the bacteria, which means it is present but not causing illness. Most pregnant women who carry GBS feel completely normal.
Why testing happens in late pregnancy
GBS testing is typically done late in pregnancy because colonization status can change. A negative test earlier in pregnancy might not be negative by the time you deliver. A positive result earlier might not stay positive. Testing closer to delivery gives the most useful information for planning labor care.
The timing also allows your care team to have results on file before delivery, which helps make decisions quickly when labor begins. If you are approaching your third trimester, our third trimester checklist can help you keep track of what to expect during this stage.
How the test is done
GBS testing is simple and quick. A swab is taken from the lower vagina and rectum. The sample is sent to a lab to see whether GBS is present. The test is not the same as a Pap smear. It is usually faster and less uncomfortable.
If you have questions about the test, or if you are nervous about it, it is a good idea to voice any concerns at your appointment.
What if I am GBS positive?
A positive GBS test means that you are carrying the bacteria at the time of testing. It does not mean you have symptoms or need antibiotics right away. The standard approach is to give antibiotics during labor, not before.
