Urinary tract infection in pregnancy

Urinary tract infections (UTIs) are common in pregnancy. Not all urine infections cause symptoms (known as asymptomatic bacteriuria) but in pregnancy even those without symptoms need to be treated.

If not treated, the risk of complications such as kidney infection (pyelonephritis), low birth weight or early labour are higher. UTIs are easily diagnosed with a urine test and treated with antibiotics.

Key points

  1. A UTI happens when any part of your urinary system – your kidneys, ureters, bladder and urethra – becomes infected by bacteria. 
  2. UTIs are common in pregnancy and do not always have symptoms.
  3. You should have a urine test early in pregnancy (when first seen) to check for signs of UTI, even if you have no symptoms.
  4. UTIs in pregnancy are easily treated with a course of antibiotics; different antibiotics are used at different stages of pregnancy.
  5. If untreated, UTIs in pregnancy can increase your risk of complications such as kidney infection, low birth weight for baby and premature birth (baby is born much sooner than the expected date).


You are more prone to UTIs during pregnancy due to the changes in hormones which slows the flow of urine. As a result, bacteria have more time to grow in the urine before being flushed out. Also, as the uterus grows, the increased weight can block the flow of urine from the 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 any of the symptoms above, as well as fever or feeling generally unwell, seek medical advice right now.
  • You may have pyelonephritis, a more serious infection of the kidneys which needs immediate treatment. 

Asymptomatic bacteruria

Not all urine infections cause symptoms. Sometimes you may have bacteria in your urine but not have any symptoms. This is called asymptomatic bacteriuria and in pregnancy, this still needs treating.¹

  • Asymptomatic bacteriuria occurs in 2% to 10% of all pregnancies.
  • If untreated, up to 30% of mothers may develop acute cystitis and up to 50% acute pyelonephritis

You should have a urine test early in pregnancy (when first seen), even if you have no symptoms, to look for asymptomatic bacteriuria.


UTIs are diagnosed by doing a urine test and looking for bacteria, red cells and white cells in the urine.

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 bacteruria: If you have no symptoms and bacteria are found in the urine. 
  • Cystitis or UTI: If bacteria is found in the urine and you have lower urinary tract symptoms.
  • Pyelonephritis: If you have the above 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 are normally treated with a course of antibiotics. When you see a health provider, always make sure they know you are pregnant as not all antibiotics or medicines are safe in pregnancy. 

The antibiotic you are prescribed will depend on what stage of pregnancy you are at. Antibiotics are very effective at clearing urinary tract infections in pregnancy, and complications are very rare.

What to expect

You should feel better in 2 to 3 days after starting the antibiotics, however:

  • It is important to finish the full course of antibiotics (usually 7 days in pregnancy). This reduces the risk of the infection recurring.
  • If you are not improving in 2 to 3 days or you develop fever, nausea, vomiting or feel unwell, contact your doctor/midwife straight away.
  • After finishing the antibiotics, you will need a further urine check one week later to check the infection has been treated properly.
  • You will then have urine tests each month while pregnant to make sure it doesn't recur.

Why treat urinary tract infections in pregnancy?

It is important to treat UTIs, 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). 


To help prevent UTIs:

  • Don't delay urinating — avoid 'holding on'.
  • Make sure your bladder is as empty as possible every time you go.
  • Women should always wipe from the front (vagina) to the back (anus) after urinating or having a bowel motion.
  • Urinating before and soon after sexual intercourse can help.
  • Drink plenty of water (1.5 to 2 litres a day) to flush bacteria out of the urethra and bladder.

Learn more

Urine infection in pregnancy Patient Info, UK


  1. Smaill FM, Vazquez JC. Antibiotics for asymptomatic bacteriuria in pregnancy. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: CD000490. DOI: 10.1002/14651858.CD000490.pub2
  2. Managing urinary tract infections in pregnancy. Best Practice Journal April 2011
  3. Wing DA, Fassett MJ, Getahun D. Acute pyelonephritis in pregnancy: an 18-year retrospective analysis. Am J Obstet Gynecol 2014; 210:219.e1. [abstract, full article]
  4. Vazquez JC, Abalos E. Treatments for symptomatic urinary tract infections during pregnancy. Cochrane Database of Systematic Reviews 2011, Issue 1. Art. No.: CD002256. DOI: 10.1002/14651858.CD002256.pub2
Credits: Editorial team, Health Navigator.