# Group B Strep Test

Source: https://www.pregnancypowerhour.com/tests/gbs-test
Last updated: 2026-07-01

> The Group B Strep (GBS) test is a routine third-trimester screening that checks for a common bacteria, helping you make informed decisions for labor.

The Group B Strep (GBS) test is a routine screening performed in your third trimester to check for the presence of a common bacteria that can be passed to your baby during birth. This test, sometimes called a GBS swab or strep B test, is a universal standard of care in countries like the US, UK, and Canada, reflecting a collaborative effort to support neonatal health.

As a birth doula, I often see how understanding these routine screenings can bring a sense of calm and clarity as you approach your birthing time. Just as an early [Dating Ultrasound](/tests/dating-ultrasound) provides a first glimpse into your pregnancy, and the [First Prenatal Blood Panel](/tests/first-prenatal-blood-panel) offers foundational health insights, the GBS test is another piece of the puzzle, designed to give you and your care team information to make informed decisions.

## What it is

Group B Strep is a common type of bacteria that can live in the intestines and lower genital tract. It's important to understand that GBS colonization is not a sexually transmitted infection, nor does it typically cause symptoms or illness in pregnant people. In fact, it's quite common, colonizing about 20–30% of pregnant individuals without them ever knowing it. The purpose of the screening is not to treat you for an infection, but to identify if the bacteria is present, as it could potentially pass to your baby during a vaginal birth.

While universal screening is the prevailing approach in many regions, it's worth noting that some European centers, particularly in the UK, sometimes opt for a risk-based screening approach. This divergence highlights that medical best practices can evolve, and the conversation around these choices is ongoing within the medical community. Ultimately, the goal is always to support the healthiest possible start for your baby.

## When and how it happens

This screening is typically performed late in your pregnancy, specifically between weeks 36 and 37. This timing is intentional, as colonization can change; a negative swab taken earlier in pregnancy doesn't guarantee a negative result closer to labor. The test itself is straightforward: a vaginal-rectal swab. In many practices, this can even be self-collected in the privacy of your provider's office, offering an element of comfort and autonomy in the process. It's a quick, generally painless procedure that provides valuable information as you prepare for birth.

## What the results mean

If your GBS test comes back positive, it means the bacteria was detected. This doesn't mean you're ill, but it does indicate that one option might be to receive intravenous (IV) antibiotics during labor. Evidence suggests that receiving IV penicillin G (or clindamycin if you have an allergy) during labor can significantly reduce the risk of neonatal GBS infection by approximately 80%. This is a proactive measure to protect your baby from potential complications. It's reassuring to know that these IV antibiotics are compatible with various birth preferences, including vaginal birth, water birth, and unmedicated birth, allowing you to maintain agency over your birthing experience.

If your test is negative, it means GBS was not detected at the time of the swab. This can offer a sense of ease as you move toward labor, knowing this particular factor is less of a consideration. Remember, every screening, from a [NIPT — Cell-Free DNA Screening](/tests/nipt-cell-free-dna) to this GBS test, is about gathering information to support your informed decisions, not about creating certainties.

## Questions worth asking

As you navigate your options, having a calm and clear conversation with your care provider is key. Here are some questions you might consider asking:

*   "Can I self-collect the swab, and what does that process involve?"
*   "What are the specific antibiotic options and administration protocols if I test positive?"
*   "How would a positive GBS result impact my birth preferences, such as a water birth or unmedicated labor?"
*   "What are the benefits and potential considerations of universal screening versus risk-based screening in this practice?"
*   "If I test negative, is there any scenario where I might still receive antibiotics for GBS during labor?"

Remember, you get to decide what feels right for you and your baby. My role as a doula is to help you feel confident and clear in those decisions, always encouraging you to consult your care provider for your specific medical situation. Grab the free first-trimester guide — link in bio.