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Infections Call your provider

Urinary Tract Infection in Pregnancy

Also known as UTI in pregnancy, Bladder infection, Asymptomatic bacteriuria, Pyelonephritis. Screened early; can occur any time, kidney infection peaks in the second trimester.

Urinary tract infections are among the most common infections in pregnancy, which makes them both more likely and more important to treat. The twist is that even a UTI with no symptoms matters here, because it can quietly climb to the kidneys and set off complications like preterm labor. So your provider tests your urine early and treats any infection found, symptoms or not, with antibiotics that are safe in pregnancy.

Know the warning signs When to call a provider
How common
Up to about 8%
Silent bladder bacteria affect 2% to 10%; bladder and kidney infections each about 1% to 2%.
When
Screened early
Urine is tested at the first prenatal visit; kidney infection peaks in the second trimester.
Urgency
Treat promptly
All are treated, even without symptoms; kidney-infection signs are urgent.
Outlook
Excellent with treatment
Safe antibiotics clear it; the risk is from leaving it untreated.

Understanding it

What is urinary tract infection in pregnancy?

A urinary tract infection is bacteria growing where they should not, in the urine, bladder, or kidneys. In pregnancy it runs along a spectrum of three forms. The mildest is asymptomatic bacteriuria: bacteria in the urine with no symptoms. Next is cystitis, a bladder infection with the familiar burning and urgency. The most serious is pyelonephritis, a kidney infection with fever and back pain. Untreated, the mild form can climb the ladder to the serious one.

Pregnancy makes UTIs more likely for physical reasons. Progesterone relaxes the urinary tract and the growing uterus presses on the bladder, so urine drains slowly and sits longer, easy ground for bacteria to multiply and travel up toward the kidneys. Pregnancy also softens the immune system a little. Together these changes leave the whole tract more vulnerable.

This is why even a symptom-free UTI is treated in pregnancy, unlike in most non-pregnant people: untreated bacteria progress to a kidney infection in roughly a quarter of cases, and kidney infections here are linked to preterm birth, low birth weight, and, rarely, serious maternal illness. Clearing the bacteria early, before symptoms even start, breaks that chain, which is why a urine culture is standard in early prenatal care.

Treatment is straightforward and safe: a short course of an antibiotic chosen for pregnancy, guided by the culture. Silent bacteriuria or a bladder infection clears with pills; a kidney infection usually needs hospital care with IV antibiotics. The key distinction is between a bladder infection, uncomfortable but not urgent, and a kidney infection, with fever and back pain, which needs to be seen right away.

Symptoms

What are the symptoms?

Symptoms depend on the form. Silent bacteriuria has none. A bladder infection causes lower urinary symptoms. A kidney infection adds fever and back pain and is the urgent one.

Early signs

  • Asymptomatic bacteriuria: no symptoms at all, found only on a urine test
  • Bladder infection: burning with urination, urgency, and frequent small amounts of urine
  • Bladder infection: pelvic or lower-belly discomfort, and cloudy or strong-smelling urine
  • Sometimes a feeling of not fully emptying the bladder

Emergency signs — call 911

  • Fever of 38 C (100.4 F) or higher with urinary symptoms, a sign the infection may have reached the kidneys
  • Pain in the back or side (flank pain)
  • Shaking chills
  • Nausea or vomiting
  • Any UTI symptoms along with contractions or signs of preterm labor

Why it matters

Risks to you and baby

Progression to a kidney infection

The main reason for early treatment. Untreated bacteria climb to the kidneys in about a quarter of cases, causing pyelonephritis, which is serious in pregnancy. Early treatment prevents it.

Preterm birth and low birth weight

Kidney infections, and untreated UTIs generally, are linked to early labor and lower birth weight. Clearing the infection lowers these risks.

Maternal illness

A kidney infection can occasionally spiral into serious whole-body illness (sepsis), which is why pyelonephritis usually means hospital care with IV antibiotics.

Recurrence

Some people get repeated UTIs in pregnancy. When that happens, a low nightly dose of antibiotic is often used to keep them away for the rest of the pregnancy.

How it's found

How is it diagnosed?

A urine culture diagnoses UTIs in pregnancy, identifying the bacteria and guiding antibiotic choice. Screening is done early, even without symptoms.

Urine culture

A clean-catch, midstream sample is grown in the lab to detect and identify the bacteria and show which antibiotics will work. This is the definitive test.

Early screening

A culture at the first prenatal visit or by 12 to 16 weeks checks for silent bacteriuria, so it can be treated before it causes problems.

Urinalysis and symptoms

A quick dipstick and your symptoms help decide when to culture and can suggest infection, but a culture confirms it and guides treatment.

Screened once early in pregnancy. Tested again any time symptoms suggest a UTI, and cultures are repeated to confirm the infection has cleared.

Treatment

How is it managed?

Treatment is antibiotics chosen to be safe and effective in pregnancy. Silent bacteriuria and bladder infections take pills; a kidney infection usually needs hospital care.

Treatment paths

Bacteria in the urine and bladder infections take a 5 to 7 day course of an oral antibiotic, chosen from the culture. Even a symptom-free infection is treated, since clearing it prevents progression. The choice is made with pregnancy in mind: nitrofurantoin and sulfa drugs are generally avoided in the first trimester when alternatives exist, and both are also avoided near delivery; fluoroquinolones are avoided throughout.

Medication

Common safe options include amoxicillin, amoxicillin-clavulanate, and cephalexin, with nitrofurantoin used outside the earliest and latest windows. The choice always follows what the culture shows the bacteria are susceptible to.

Monitoring

A follow-up culture confirms the infection is gone. For repeated UTIs, a low daily suppressive dose is often continued through pregnancy. Group B strep found in the urine also signals the need for antibiotics in labor.

Can it recur?

UTIs recur in a minority of people, and having had one makes another likelier. After two or more, suppressive antibiotics prevent further infections. Treatment does not affect delivery timing; the concern is only that an untreated infection could trigger early labor.

What you can do

Can it be prevented?

  • Get your early urine screening

    The routine urine culture early in pregnancy does the most: it finds and clears silent bacteria before they can reach the kidneys.

  • Finish the full antibiotic course

    Take every dose even after you feel better, and complete any follow-up culture, so the infection clears fully and does not return.

  • Stay hydrated and empty your bladder

    Drinking plenty of water, not holding urine, and emptying your bladder fully, including after sex, all help flush bacteria out. These are helpful additions, not a substitute for antibiotics.

  • Report symptoms early

    Burning, urgency, or frequency should prompt a call so a bladder infection is treated before it reaches the kidneys. Do not wait it out.

Who is more at risk

Risk factors

Pregnancy itself
The hormonal and physical changes of pregnancy slow urine flow and raise the baseline risk for everyone, which is why screening is universal.
A history of UTIs
Having had UTIs before, in or out of pregnancy, makes them likelier again and raises the chance of recurrence.
Diabetes
Diabetes, including gestational diabetes, raises the risk of UTIs and of a kidney infection.
Other factors
A first pregnancy, younger age, obesity, and smoking are associated with a higher risk of kidney infection in pregnancy.

Do not wait

When to call your provider or 911

  • Seek care right away for a fever of 38 C (100.4 F) or higher with urinary symptoms, which can mean the infection has reached your kidneys.
  • Go in urgently for back or side pain, shaking chills, or nausea and vomiting with a UTI.
  • Call promptly for burning, urgency, or frequent urination, so a bladder infection can be treated early.
  • Seek care if you have UTI symptoms along with contractions or other signs of preterm labor.
  • Let your provider know if UTIs keep coming back, so suppressive treatment can be considered.

Talking to your team

Questions to ask your provider

  • Did my early urine screening show any bacteria that need treating?
  • Which antibiotic is safe for me at this stage of pregnancy?
  • How will I know if a bladder infection has spread to my kidneys?
  • Do I need a follow-up culture to confirm it cleared?
  • If I keep getting UTIs, should I be on a preventive dose?
  • If group B strep was in my urine, what does that mean for labor?

Keep reading

More on urinary tract infection in pregnancy

All pregnancy guides articles

Good to Know

Urinary Tract Infection in Pregnancy FAQs

Common questions about urinary tract infection in pregnancy, answered.

Why treat a UTI if I have no symptoms?

Because in pregnancy, unlike most other times, silent bacteria in the urine matter. Left untreated, they reach the kidneys in about a quarter of cases, and a kidney infection here is linked to preterm birth and serious illness. Clearing the bacteria early, before symptoms start, prevents that, which is why your urine is cultured early even when you feel fine.

Are UTI antibiotics safe in pregnancy?

Yes, the ones your provider chooses are. Several are safe and effective in pregnancy, such as amoxicillin and cephalexin, with the choice guided by your culture. A few, like certain sulfa drugs and nitrofurantoin, are avoided at particular times, and fluoroquinolones are avoided altogether. Leaving a UTI untreated is riskier than the antibiotic.

How do I know if it has spread to my kidneys?

A bladder infection causes burning, urgency, and frequency but no fever. A kidney infection adds whole-body signs: a fever of 38 C or higher, back or side pain, shaking chills, and nausea or vomiting. Those mean you should be seen right away, since a kidney infection in pregnancy usually needs hospital care with IV antibiotics.

Can a UTI cause me to go into labor early?

An untreated one can, yes, especially a kidney infection, which is linked to preterm labor. That is why UTIs are screened for and treated promptly. A treated infection is very unlikely to affect your delivery, so the priority is catching it early.

Why do I keep getting UTIs now that I am pregnant?

Pregnancy slows urine flow, since hormones relax the urinary tract and the uterus presses on the bladder, giving bacteria more time to multiply. Some people get repeated infections. After two or more, your provider may prescribe a low nightly dose for the rest of the pregnancy.

Can I prevent UTIs in pregnancy?

You can lower the risk. The biggest step is the routine early screening, which catches silent infection. Drinking plenty of water, not holding urine, emptying your bladder fully, and urinating after sex all help flush bacteria out, but they support rather than replace the antibiotics that clear an actual infection.

Is cranberry juice a treatment?

No. Cranberry may modestly help some people avoid UTIs, but it does not treat one, and in pregnancy a UTI needs antibiotics to clear it and keep it from reaching the kidneys. Do not wait it out; with symptoms or a positive test, take the prescribed antibiotics.

What does group B strep in my urine mean?

Group B strep in the urine is treated as a UTI and also flags heavy colonization, so you will get antibiotics during labor to protect your baby, regardless of your later GBS swab. It changes your delivery plan, so your provider notes it in your record.

Medically Reviewed · Updated

Reviewed by Dr. Grace Lin, MD, FACOG · OB-GYN

Obstetrician-gynecologist focused on reproductive and sexual health for women: pregnancy, BV, yeast, trichomoniasis and HPV/cervical screening. Our editorial guidelines →

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