- GBS is a common bacteria — 20–30% of pregnant women carry it. It is not an STI and does not mean your partner is unwell.
- The risk is during birth: without antibiotics, roughly 1 in 200 babies gets a GBS infection. With IV antibiotics in labor, that drops to around 1 in 4,000.
- The main change to the birth plan: arrive at hospital when labor starts — don't labor at home for hours — so antibiotics have time to work.
- When you walk into triage, say it out loud: "She is GBS positive." Even if you assume they have the notes, say it anyway.
- Watch baby closely in the first 24 hours and up to 7 days for signs of infection: fever, fast breathing, poor feeding, limpness, high-pitched cry.
The call came at 36 weeks. The midwife's voicemail said your partner's Group B Strep test had come back positive. Please call to discuss.
You listen to it twice. You have no idea what Group B Strep is. You don't know whether to wake your partner to tell her, or whether this is something to bring up calmly at breakfast. You don't know how worried to be. And you definitely don't know what it means for the birth that is now — suddenly, viscerally — four weeks away.
This is what it means. And here's what you need to do.
What GBS actually is
Group B Streptococcus is a bacteria that lives naturally in the gut and lower reproductive tract. It is not a sexually transmitted infection. It is not a sign that anything has gone wrong. It is not a new infection — it's been there, as part of the normal bacterial environment of the body, and the test simply found it.
About one in four pregnant women carries GBS. Most carriers are completely healthy — no symptoms, no illness, nothing to treat. The bacteria causes them no harm at all.
The specific concern is this: during a vaginal birth, a baby passing through the birth canal can pick up the bacteria. For most babies that exposure is harmless. But for a small number, GBS can cause a serious infection — pneumonia, meningitis, or sepsis — usually within the first 24 hours after birth.
GBS is not an infection in the usual sense. Your partner isn't sick. She is a carrier. The only clinical significance is what happens during birth — and that is very manageable.
The test, and what a positive result actually means
In the US, a routine swab is taken between 36 0/7 and 37 6/7 weeks, per CDC guidance. (In the UK NHS, GBS screening is risk-based rather than universal, though this is evolving.) It's a swab — vaginal and rectal — and results come back within roughly 48 hours. Entirely routine. Many women don't even remember it being done alongside everything else at that point in pregnancy.
A positive result means she carries the bacteria. That's it. It doesn't tell you the quantity. It doesn't mean the baby is at high risk right now. It means the birth plan gets one important addition.
The treatment — and what changes (and what doesn't)
The intervention is straightforward: IV antibiotics, started when labor begins, given through labor at regular intervals (typically every 4 hours). The goal is at least four hours of antibiotic cover before delivery — that's when the protection is strongest.
The IV doesn't mean she's stuck in bed. The pole is on wheels. She can walk. She can use the birth pool between doses — many hospitals are fine with this. She can move freely in the room. It's an inconvenience, not a restriction.
What actually changes about the birth plan? Mostly one thing: arrival time. If you were planning to labor at home for several hours before going in, that plan needs to change. When labor starts — real contractions, regular and strengthening — you go in. Because the antibiotics need time, and that time starts when the drip goes in.
- She can still have an unmedicated birth if that's the plan
- She can still use the birth pool (usually between antibiotic doses)
- She can still move freely and use different positions
- A C-section may not require antibiotics if performed before labor and before waters break
- She can still have delayed cord clamping, skin-to-skin, all of it
Your job during all of this — specifically
There are three things I'd tell every dad in this situation. They're practical. They matter.
Know the status before labor starts. Don't let this information live only on the midwife's records. Know it yourself. The result, when it came, what it means for the birth. If your partner is in active labor and you're doing the talking, you need to have this ready.
Say it out loud when you arrive at triage. Even if you assume they have the notes, say it anyway. The first thing you say — before anything else — is: "She is GBS positive." Say it directly to the midwife on arrival. This is not dramatic. It is important.
Watch the baby in the first week. With antibiotics given in time, the risk is very small. But GBS infection in a newborn can appear within hours, or up to seven days after birth. The early-onset type (first 7 days, most commonly day one) is the one associated with labor. Late-onset GBS (7 days to 3 months) is rarer but possible.
Even if you assume they have the notes, say it anyway: "She is GBS positive." Say it first. Don't wait for someone to ask.
What to watch for in the baby after birth
Most newborns with GBS exposure are completely fine. But knowing the signs means you catch it fast if something does develop.
In the first 24 hours, and up to 7 days, watch for: fever or temperature instability, fast or labored breathing, poor feeding or unusual reluctance to feed, limpness or floppy muscle tone (not normal newborn squishiness — noticeably low tone), a high-pitched or unusual cry, or the baby being very difficult to wake.
Any of these: call your midwife or go straight to the hospital. Don't wait and see. GBS infections, when caught early, are treated effectively with antibiotics. The outcomes when caught promptly are good. The danger is in waiting.
Early-onset GBS appears within the first 7 days — most commonly within the first 24 hours. It is associated with transmission during birth. This is what IV antibiotics in labor prevent. Late-onset GBS (7 days to 3 months) can occur even when birth went well and antibiotics were given. It is less common. The signs are the same: fever, fast breathing, poor feeding, unusual limpness. Always contact your healthcare provider if you're concerned.
A note on birth plans and keeping things calm
The GBS result, when it arrives, often comes by letter or through a patient portal, with no context and no explanation. Just a positive result and some medical terminology. If you've been using Dadly to track the pregnancy, you can put the result straight into the app and get a plain-English explanation of what it means for your specific week and situation — rather than falling into a Google spiral at 11pm.
If you're preparing for the delivery room and want to know what to expect more broadly, our guide on what to expect in the delivery room as a first-time dad covers the whole picture. And if you're putting together your hospital bag, the hospital bag checklist for dad has everything you'll want to have ready.
For a broader look at where you are at this point in the pregnancy, the week 28 pregnancy guide for dads covers what's happening in the third trimester and how to prepare. And if the GBS result came to you through a medical report or letter and you'd like to understand it fully, using AI to understand pregnancy scan and lab results explains exactly how to approach that.
The positive result felt alarming. It is manageable. The system has a clear protocol, and the protocol works. Your job is to know the plan, say the words at triage, and watch the baby carefully in the first week. That's it.