Urinary tract infection (UTI) in pregnancy (Pokenga pūaha mimi)

Key points about urinary tract infection in pregnancy

  • Urinary tract infections (UTIs) are common in pregnancy.
  • They happen when any part of your urinary system – your kidneys, ureters, bladder and urethra – becomes infected by bacteria. 
  • UTIs in pregnancy are more likely to cause complications. 
  • You should have a urine culture test early in pregnancy (when first seen) to check for signs of UTI, as they don't always have symptoms.
  • UTIs are easily treated with a course of antibiotics. Your healthcare provider will choose an antibiotic that's safe to use during pregnancy.
  • If untreated, UTIs in pregnancy can increase the risk of complications for you and your pēpi. 
Pregnant couple kissing on grassy dunes by beach

You are more prone to UTIs during pregnancy due to changes in your hormones, which slows the flow of urine (pee or mimi). As a result, bacteria have more time to grow in your urine before being flushed out. Also, as the uterus grows, the increased weight can block the flow of urine from your bladder, causing an infection. 

Common symptoms of a urinary tract infection are:

  • pain when you pass urine
  • passing urine more often (urinary frequency)
  • pain in the lower stomach area (abdomen)
  • blood in your urine (haematuria)
  • urine that looks cloudy or smells more than normal.
Warning signs
If you have a high fever, shakes, back pain or feel generally unwell, with or without urinary symptoms, seek medical advice right now. You may have pyelonephritis, a more serious infection of the kidneys which needs immediate treatment. 

Asymptomatic bacteriuria

Not all urine infections cause symptoms. Sometimes you may have bacteria in your urine but not have any symptoms. This is called asymptomatic (having no symptoms) bacteriuria (but bacteria are found). In non-pregnant women this is usually harmless, but in pregnancy this needs treating.

  • Asymptomatic bacteriuria occurs in 2% to 10% of all pregnancies.
  • If untreated, up to 30% of mothers may develop acute cystitis and up to 2–3% pyelonephritis.

UTIs are diagnosed by doing a urine culture test that looks for bacteria, red cells and white cells in your urine (pee or mimi). This is usually done in the first trimester and is different to the urine test to see if you are pregnant. 

Your doctor will send a sample of your urine to the laboratory to be tested. If bacteria are found in the urine, the sample will be cultured and tested for antibiotic sensitivities to check which antibiotics will work best.

What do my results mean?

  • Asymptomatic bacteriuria: Where you have no symptoms and bacteria are found in your urine. 
  • Cystitis or UTI: Where bacteria are found in your urine and you have lower urinary tract symptoms.
  • Pyelonephritis: If you have the above symptoms, and also have symptoms or signs of fever or feeling unwell, this may indicate upper urinary tract infection such as pyelonephritis

Your doctor will discuss your results and the appropriate treatment for your situation with you.

UTIs in pregnancy are treated with antibiotics, even if you have no symptoms. If left untreated, UTIs can progress to cause a serious kidney infection known as pyelonephritis. They have also been linked with higher rates of low birth weight of the baby and premature birth (baby is born much sooner than the expected date). 

When you see a health provider, always tell them you are pregnant as not all antibiotics or medicines are safe in pregnancy. 
  • Your doctor will choose an antibiotic that is safe to use during your stage of pregnancy. The most commonly recommended antibiotic is nitrofurantoin. Usually, a 7-day course of antibiotics is prescribed. You should finish the whole course to completely treat the infection and reduce the chance of it coming back.
  • Your symptoms should begin to improve within a few days, if you had any. If you still have symptoms for more than 2 days after starting treatment, or you get worse, see your doctor as soon as possible.
  • After finishing the antibiotics, you will need a further urine check 1 week later to check the infection has been treated properly.
  • You will then have urine tests each month while pregnant to make sure the UTI doesn't come back.

  • Take paracetamol for pain (use the lowest dose for the shortest possible time).
  • Do not use any non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen in pregnancy.
  • Drink plenty of water to avoid dehydration and help flush out the bacteria.
  • No evidence has been found for taking products that alkalise your urine (such as Ural®).
  • Cranberry juice is not a recommended treatment as as clinical studies have not shown that it is effective.
  • Results from research into D-mannose are also not convincing.


  • Do wipe from front to back when you go to the toilet.
  • Do try to fully empty your bladder when you pee.
  • Do drink plenty of fluids.
  • Do take showers instead of baths.
  • Do wear loose cotton underwear.
  • Do pee as soon as possible after sex.


  • Don't use perfumed bubble bath, soap or talcum powder.
  • Don't hold your pee in if you feel the urge to go.
  • Don't wear tight, synthetic underwear, such as nylon.
  • Don't wear tight jeans or trousers.

  1. Smaill FM, Vazquez JC. Antibiotics for asymptomatic bacteriuria in pregnancy(external link) Cochrane Database of Systematic Reviews. 2007;2:CD000490.
  2. Managing urinary tract infections in pregnancy(external link). BPAC, NZ, 2011
  3. Wing DA, Fassett MJ, Getahun D. Acute pyelonephritis in pregnancy: an 18-year retrospective analysis(external link) Am J Obstet Gynecol. 2014;210.e1.
  4. Vazquez JC, Abalos E. Treatments for symptomatic urinary tract infections during pregnancy(external link). Cochrane Database of Systematic Reviews. 2011;1CD002256.
  5. Urinary tract infections(external link) NHS, UK, 2017
  6. Kazemier BM, Koningstein FN, Schneeberger C, et al. Maternal and neonatal consequences of treated and untreated asymptomatic bacteriuria in pregnancy: a prospective cohort study with an embedded randomised controlled trial(external link) Lancet Infect Dis. 2015 Nov;15(11):1324-33.
  7. Gágyor I, Bleidorn J, Kochen MM et al. Ibuprofen versus fosfomycin for uncomplicated urinary tract infection in women: randomised controlled tria(external link)l BMJ. 2015;351:h6544.
  8. Kronenberg A, Bütikofer L, Odutayo A, et al. Symptomatic treatment of uncomplicated lower urinary tract infections in the ambulatory setting: randomised, double blind trial(external link) BMJ 2017;359:j4784.
  9. Cranberries for preventing urinary tract infections(external link) Cochrane Database of Systematic Reviews, 2012. (no benefit found in pregnancy)
  10. Kranjčec B, PapešD, Altarac S.D-mannose powder for prophylaxis of recurrent urinary tract infections in women: a randomized clinical trial(external link) World J Urol. 2014 Feb;32(1):79-84. Epub 2013 Apr 30.

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Reviewed by: Dr Jeremy Steinberg, FRNZCGP

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