- Azithromycin during childbirth cuts serious infections in moms
- But it raises antibiotic resistance in nasal bacteria for months
- Effect fades after a year — not yet a long-term threat
This could change how we balance infection protection and antibiotic safety in childbirth.
A woman goes into labor. She’s healthy, but infections during delivery are a real danger. Doctors give her an antibiotic to be safe. It helps prevent life-threatening illness. But what if that same medicine makes bacteria in her body harder to treat later?
That’s exactly what researchers are now tracking — not just in mothers, but in newborns too.
Millions of women give birth each year without complications. But around the world, infections after childbirth still cause too many deaths. In some regions, sepsis (a dangerous body-wide response to infection) is a leading cause of maternal death.
Giving antibiotics during labor — even when no infection is present — has been tested as a shield. One drug, azithromycin, showed promise. It reduced maternal deaths and infections in a large global trial.
But antibiotics come with a hidden cost: they can fuel resistant bacteria. These are germs that no longer respond to common drugs. Once resistance spreads, even simple infections become harder to treat.
And now, a new study shows azithromycin given during labor does lead to more resistant bacteria — at least for a while.
The Surprising Shift
For years, doctors believed short-term antibiotic use was low-risk. A single dose? Probably safe. But recent science says even brief exposure can shift the bacteria living in our bodies.
We all carry bacteria in our nose, skin, and gut. Most are harmless — or even helpful. But when antibiotics kill off the sensitive ones, resistant strains can take over.
The A-PLUS study originally found azithromycin helped protect mothers. But it didn’t answer the big question: what happens to bacteria after the drug is given?
Now, this follow-up study zooms in on that risk.
What Scientists Didn’t Expect
Researchers looked at nasal swabs from nearly 1,000 women and their babies across seven countries. They checked for two common bacteria: Staphylococcus aureus (often called “staph”) and Streptococcus pneumoniae.
These bugs can live quietly in the nose — or turn dangerous, causing pneumonia or bloodstream infections.
Women who got azithromycin were more likely to carry azithromycin-resistant staph in their noses — not right away, but in the weeks and months after birth.
At day 7, 6 weeks, and 3 months, resistance levels were significantly higher in the azithromycin group compared to those who got placebo.
And here’s the catch: babies showed the same pattern.
Infants born to mothers who got the antibiotic also had higher resistance at 6 weeks.
This doesn’t mean this treatment is available yet.
Think of bacteria like cars stuck in traffic. Antibiotics are roadblocks. Most cars (normal bacteria) can’t get through and disappear.
But a few cars have GPS reroutes — these are the resistant ones. With less traffic, they take over the road.
Azithromycin acts like a temporary roadblock. It clears space by killing off sensitive bacteria. But in that open space, resistant staph can grow and spread.
The drug doesn’t cause mutations. Instead, it gives resistant strains a chance to thrive — just by removing their competition.
This effect isn’t permanent. Over time, without more antibiotic pressure, the balance shifts back.
The Hidden Timeline
The study followed women and babies for a full year. Swabs were taken during labor, then at 7 days, 6 weeks, 3, 6, and 12 months.
Scientists grew bacteria from nasal samples and tested how well azithromycin could stop them.
They focused on S. aureus and S. pneumoniae — two bugs known to cause serious infections.
Results showed a clear spike in resistance in both moms and babies — but only for a limited time.
By 6 weeks, women who got azithromycin were much more likely to carry resistant staph in their noses. The same was true for their infants.
At 3 months, the difference in moms was still noticeable. But by 6 months, resistance levels began to drop.
By 12 months, there was no significant difference between the azithromycin and placebo groups.
For babies, the effect was shorter. Higher resistance appeared only at 6 weeks. After that, levels dropped and stayed low.
As for S. pneumoniae, there wasn’t enough data. Too few samples grew in the lab. So no firm conclusions could be drawn.
Still, the staph findings are clear: azithromycin use leads to temporary resistance.
That’s Not the Full Story
This isn’t the first time antibiotics have been linked to resistance. But it’s one of the first large studies to track both mothers and babies over time — across multiple countries.
The rise in resistance is real. But so is the drop.
The body’s bacterial balance appears to recover within a year. That’s reassuring.
Still, even short-term resistance matters — especially in places where antibiotics are scarce or infections spread fast.
This study doesn’t say we should stop using azithromycin in childbirth. Instead, it shows we must weigh benefits and risks carefully.
In high-risk settings, preventing maternal infection may outweigh the temporary rise in resistance.
But in low-risk births, the math might be different.
The findings support a “right drug, right time” approach — using antibiotics only when the benefits clearly outweigh the risks.
If you’re pregnant or planning a pregnancy, this doesn’t mean you should refuse antibiotics if needed.
But it does mean doctors should think twice before giving them routinely.
Azithromycin is not standard in most hospitals — yet. These results may help guide future guidelines.
Talk to your provider about infection prevention and antibiotic use during birth. Ask: Is this necessary for me?
The Real Cost
The study has limits. It only looked at nasal bacteria — not infections. It didn’t track whether resistant bacteria actually caused illness.
Also, most data came from S. aureus. S. pneumoniae results were too sparse to interpret.
And while the study was large and global, it wasn’t designed to measure long-term health outcomes.
Still, the signal is strong: antibiotics change our internal ecosystems — even for a short time.
More research is needed to understand when — and for whom — the benefits of azithromycin outweigh the risks.
Future studies may look at different doses, timing, or alternative drugs.
For now, this study adds a crucial piece to the puzzle: protection from infection comes with a temporary trade-off. But the body can bounce back.
