Kidney Infection While Pregnant: Symptoms, Risks, And Treatments

There are around 250,000 cases¹ of kidney infections in the United States each year. While anyone of any age can develop a kidney infection, they are much more common among women, especially during pregnancy. 

Pregnant women need to speak to their doctor if they are experiencing any of the signs of a kidney infection or urinary tract infection (UTI) to prevent the risk of complications. If you are pregnant, ensure you know what symptoms to watch for and when you should contact a doctor if you suspect a kidney infection.

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Kidney infection while pregnant

Kidney infections, also known as pyelonephritis, usually only affect one of your two kidneys, though in rare cases, it may affect both kidneys simultaneously. While viral infections may cause these infections, they are more often caused by bacteria entering the urinary tract. 

The bacteria can cause a UTI and infection in the bladder or the kidneys. About 1 out of every 30² UTIs results in kidney infection. Pyelonephritis affects between 0.5% and 2%³ of pregnancies.

UTIs and pyelonephritis are more common in pregnant women due to hormonal and physical changes in the body. These infections are often very treatable, usually through antibiotics taken at home, which are safe during pregnancy. 

Suppose a UTI infection doesn’t respond to the antibiotics, or your symptoms worsen, leading to a kidney infection. You may need to stay in the hospital for intravenous antibiotics, hydration, and monitoring. UTIs on their own do not typically require IV antibiotics.

If you are pregnant, it’s important to mention any symptoms of a UTI or kidney infection to your doctor. If untreated, you are more likely to have your baby early or have a baby with a low birth weight.

These conditions could increase your baby’s risk of anemia, breathing problems, infection, and other medical conditions.

Symptoms of a UTI during pregnancy

The following symptoms characterize a UTI:

  • Difficulty urinating

  • Urinating frequently

  • Feeling the need to urinate, then not passing any urine

  • Urine that is an unusual color or odor

  • Bloody urine

  • Burning or stinging when you urinate (painful urination)

  • Abdominal cramps

  • Pain during sexual intercourse

Symptoms of pyelonephritis during pregnancy

If you have pyelonephritis during pregnancy, you’ll also experience UTI symptoms. These often include the following:

  • Fever

  • Chills

  • Pain in the back, side, or groin

  • Nausea and vomiting

Call your primary care physician or obstetrician if you are experiencing any of these symptoms. They can confirm your diagnosis after examining you and doing simple tests and start you on an appropriate treatment plan as soon as possible. 

Causes of pyelonephritis during pregnancy 

Any condition that causes urine to flow from the bladder to the kidneys can cause a kidney infection. This can include kidney stones, tumors, or other blockages within the structure of the urinary tract.

However, kidney infections are more common during pregnancy because of changes in the body. The expanding uterus can put pressure on the urinary system, and the muscles supporting your kidney, bladder, ureters, and urethra will relax as the pregnancy continues. 

This can cause these structures to change position and make room for your growing baby. The uterus will also start to enlarge, putting more pressure on the urinary system and causing you to urinate more often. 

This will also cause the urethra, the tube through which urine passes, to stretch out. The pressure on the ureters can result in some urine being left behind when you empty your bladder. 

Normally, the ureters help move urine away from the kidneys and out of the body. Pregnancy hormones cause these muscles to relax, making it easier for stale urine to move into the kidneys and carry bacteria with it. 

This can cause the kidneys to swell with urine. It’s a condition called hydronephrosis,⁴ which occurs in around 80%⁵ of pregnancies. This condition may not result in an infection.

However, it does increase the risk of developing one as it makes it easier for bacteria to move from the intestine to the kidneys via the urethra. The bacteria that most often causes a UTI is E. coli.⁶

Risk factors of kidney infection while pregnant

You may be at an increased risk of pyelonephritis during pregnancy if:

  • You have a history of urinary tract infections

  • You have a family history of UTI

  • You have gestational diabetes

  • You’ve had difficulty controlling your urine (such as when coughing or sneezing)

  • You frequently have sexual intercourse

  • You use incorrect toileting techniques when wiping with toilet paper after opening your bowels

How is kidney infection diagnosed during pregnancy?

The symptoms of a kidney infection, including abdominal pain, fever, chills, and urinary symptoms, can be symptoms of other common infections. 

Your doctor will want to take a complete medical history and perform tests to determine if your symptoms are due to a kidney infection or another medical condition. 

To diagnose a kidney infection, your doctor may do the following: 

Ask about your medical history

Your doctor will want to know about any previous urinary tract infections and your family’s history of UTIs and kidney infections.

Do a physical examination

This might involve feeling your abdomen for areas of tenderness. 

Ask you to undergo testing 

Urine tests can tell your doctor whether there are any bacteria in your urine. A urine dipstick test in the doctor’s office can immediately indicate a UTI or kidney infection, and treatment can be started immediately. 

Sending the urine sample to the lab for further testing can confirm the infection and which bacteria is causing it to verify that you are on the correct antibiotics to treat it.

A blood test will show a high white blood cell count, which can signify infection. 

Your doctor may also ask you to undergo imaging tests. An ultrasound will allow your doctor to see your kidneys. This can help them detect any blockages contributing to the infection causing pain or whether your kidneys have a lot of fluid in them. 

If a doctor finds you have a UTI, they will typically send you home with oral antibiotics. However, if it has progressed to a kidney infection, you will likely need IV antibiotics in a hospital, IV fluids, and careful monitoring of your unborn baby.


The most common treatment for a kidney infection is antibiotics. If caught early enough, your doctor may give you a prescription for antibiotics to take at home, although this is rare. A hospital visit is much more likely. 

If you are showing signs of dehydration or sepsis, or if you are having contractions, you will be admitted to the hospital. In the hospital, you will get fluids to help you rehydrate and intravenous antibiotics to help fight the infection.

In most cases, your symptoms will go away after 3–5 days of receiving IV antibiotic treatment in the hospital. A doctor may prescribe oral antibiotics after you are discharged. Be sure to take all the prescribed medications.

If your symptoms don’t improve or you start to feel worse, contact your doctor immediately. They may need to change you to another type of antibiotic or perform further tests to make sure you are on the correct medication. 

Can pyelonephritis be prevented during pregnancy?

It’s not uncommon to experience UTIs throughout your pregnancy, but pyelonephritis is less common, especially if your UTI is detected and treated early. 

If your UTI comes back after antibiotic treatment, your doctor may recommend taking a small dose of antibiotics daily throughout the pregnancy to help prevent recurring infections. 

Additionally, there are things you can do at home to help prevent a UTI or kidney infection while pregnant: 

  • Drink a lot of water; aim for between 64 and 96 ounces a day⁷ 

  • Urinate when the urge arises, as holding in your urine could send more bacteria to the kidneys

  • Practice good sexual hygiene; wash before having sex and urinate soon after 

  • Wipe from front to back, as this helps prevent bacteria from the bowels from entering the urinary tract

Complications of kidney infection during pregnancy

Complications of kidney infection during pregnancy can include: 

  • Premature birth

  • Low birth weight

  • Sepsis

  • Kidney damage

  • Adult respiratory distress syndrome

It’s essential to start treatment as soon as possible for a kidney infection to prevent complications.

When to visit a doctor

Contact your doctor immediately if you are experiencing any kidney infection symptoms, including fever, chills, abdominal pain, painful urination, or blood in your urine. They can begin testing to determine if you have a kidney infection or other medical condition contributing to your symptoms. 

Early treatment is essential, as an untreated kidney infection can cause damage to the urinary system and may put your baby at risk of being born premature or underweight. 

The lowdown

Kidney infections, also known as pyelonephritis, can be more common in pregnancy due to hormonal and physical changes within the body. 

Additional pressure on the urinary system from the enlarged uterus and expansion of the kidneys and bladder can cause urine to pass from the bladder back into the kidneys, introducing bacteria into the kidneys that can lead to an infection. 

Symptoms of a kidney infection may include fever, chills, abdominal pain, painful urination, and blood in the urine. Your doctor can diagnose a kidney infection by doing a urinalysis. This involves testing your urine sample to see if there is an infection. 

You can help prevent a kidney infection by drinking plenty of fluids, urinating as soon as possible, and practicing good personal hygiene. If you are experiencing any symptoms of a kidney infection, contact your doctor immediately.

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