Can Kidney Infection Cause Miscarriage?

Are you pregnant and googling if kidney infection during pregnancy is serious? Girl, you are NOT ALONE. This has been one of the most common searches among females when it comes to google health questions lately and I totally understand why. Having a kidney infection when you’re pregnant can be serious business.

It’s NOT something you should ignore during pregnancy. Left untreated it can cause severe complications which is why KNOWING the facts (not just googling worst case scenarios!) can make all the difference. So let’s talk about it. 

What Is a Kidney Infection, and Why Does Pregnancy Make It More Likely?

Pyelonephritis is a kidney infection or, more specifically, a UTI of the upper urinary tract that occurs when a bladder infection spreads to one or both kidneys. It usually begins as a lower tract infection or asymptomatic bacteriuria (the presence of bacteria in urine without symptoms).

Pregnancy creates the perfect conditions for these infections to take hold and escalate. Here is why:

• Progesterone relaxes smooth muscle, which slows down the flow of urine through the ureters (the tubes connecting your kidneys to your bladder).

• The growing uterus physically presses on the ureters, causing urine to pool rather than drain efficiently.

• Immune function shifts during pregnancy to protect the foetus, which leaves you more vulnerable to infections generally.

• Increased glucose and protein in the urine infection during pregnancy give bacteria more to feed on.

The result? Untreated asymptomatic bacteriuria is a risk factor for developing acute cystitis (in around 40% of cases) and pyelonephritis (in 25–30% of cases) during pregnancy.

Kidney infections affect up to 2% of pregnant women, and they are one of the most common reasons for hospital admission during pregnancy.

Does Kidney Infection Cause Miscarriage?

This is the question most women want answered directly, so here it is:

Kidney infection by itself has never been directly correlated as a cause of miscarriage. Doctors will tell you there is no concrete clinical evidence that pyelonephritis can cause you to lose your pregnancy in the first trimester if treated quickly.

While a UTI can't cause you to miscarry it CAN lead to complications that will. That is why it is so important to treat it right away.

If you were to ask me what I am worried about with kidney infection it would be what happens if it progresses or goes untreated. Eventually it can lead to sepsis. Then you are putting yourself and the baby at risk.

Here is the distinction worth understanding:

• Treated kidney infection with appropriate antibiotics, the pregnancy outcome is generally good.

• Untreated or severe kidney infection can progress to sepsis, preterm labour, or in the worst cases, pregnancy loss.

  
  

How Kidney Infection in Pregnancy Can Lead to Complications

The Link Between Pyelonephritis and Preterm Labour

The most consistently documented pregnancy risk from kidney infection is preterm labour not miscarriage. Pyelonephritis has serious consequences in pregnancy, including preterm birth, anaemia, sepsis, disseminated intravascular coagulation, and acute respiratory distress syndrome.

According to some studies, around 20 to 40% of pregnant women with pyelonephritis have preterm births, and these infants are at the highest risk of complications in resource-poor settings.

When Sepsis Becomes the Danger

Sepsis, a severe, body-wide response to infection, is the most dangerous potential consequence of an untreated kidney infection. Once infection becomes systemic, a woman's condition can deteriorate extremely rapidly over the course of a few hours into septic shock, disseminated intravascular coagulation, and multi-organ failure.

Sepsis during pregnancy carries risks for both the mother and the baby, including fetal distress and, in severe cases, loss of the pregnancy.

What the Research Says About Miscarriage Specifically

Kidney infection does not appear to have evidence directly causing miscarriage in most cases. Diseases known to cause kidney injury in pregnancy like lupus nephritis or Sjogren's syndrome may lead to miscarriage, usually in the first trimester. But kidney infection causing pregnancy loss does not typically involve autoimmune disease. It's been damaged due to lupus or SS disease. The most common route from kidney infection to pregnancy loss is through sepsis/severe illness.

Recognising a Kidney Infection in Pregnancy

Spotting a kidney infection early is the single most effective way to prevent it from escalating. The tricky part is that some symptoms overlap with normal pregnancy discomfort.

Symptoms that may suggest a kidney infection include:

• High fever (38°C or above)

• Chills and shivering

• Pain in the lower back, side, or flank often one-sided

• Nausea and vomiting

• Burning or pain when urinating

• Frequent or urgent need to urinate

• Cloudy or foul-smelling urine

• General feeling of being unwell

A diagnosis of pyelonephritis should be suspected when fever of 38°C or higher is present alongside urine test results suggesting a UTI, with additional symptoms of upper urinary tract infection such as flank pain or tenderness over the kidney area.

If you have any of these symptoms during pregnancy, contact your midwife or doctor the same day. Do not wait to see if they improve on their own.

How Is a Kidney Infection Treated in Pregnancy?

Treatment depends on the severity, but kidney infections in pregnancy are taken seriously from the outset.

Guidelines suggest that pyelonephritis in pregnancy should be managed initially as an inpatient. Antibiotics should be started empirically to target organisms most likely to cause infection, be well tolerated by the mother and fetus, and penetrate well into kidney tissue. Treatment should continue parenterally until the patient begins to improve clinically, with 14 days of total antibiotic coverage.

In practical terms, this usually means:

1. Hospital admission for monitoring and IV fluids

2. Intravenous antibiotics to start treatment quickly

3. Switching to oral antibiotics once symptoms improve and you can tolerate them

4. Completing the full 14-day course stopping early increases the risk of the infection returning

5. Follow-up urine culture to confirm the infection has cleared

Some clinicians will then recommend suppressive antibiotic therapy for the remainder of the pregnancy to reduce the risk of recurrence.

Why Early Screening Matters So Much

One thing that The NHS and Obstetricians do really well is screening for asymptomatic bacteriuria early on in pregnancy. The majority of women who have bacteria growing in their urine are completely unaware of it.

Rates of subsequent pyelonephritis have fallen from 20–35% to 1–4% since screening and treating asymptomatic bacteriuria in pregnancy became routine.

Asymptomatic bacteriuria screening should be carried out at an early prenatal visit with a midstream urine culture. Detecting bacterial colonisation with a simple urine test at your booking appointment can stop it progressing to a full kidney infection.

It’s initiatives like this that make antenatal care with teams such as those here at myGynaePlus so great. Obstetric and gynaecology care is combined with early pregnancy advice and ultrasound services at our West London clinic. This means problems such as UTIs and kidney infections can be detected, monitored and managed as part of your pregnancy care rather than being treated separately.

Risk Factors for Kidney Infection During Pregnancy

Pyelonephritis during pregnancy occurs more commonly in some women. Understanding your risk factors can help you pay closer attention to early signs and symptoms.

Risk factors include sickle cell disease, diabetes mellitus, anemia, structural kidney disease of kidney, history of urinary tract infection, sexual activity, low socio-economic status.

Additional factors include:

• Having had a kidney infection in a previous pregnancy

• Recurrent UTIs before pregnancy

• Kidney abnormalities or structural issues

• Being immunocompromised

If you fall into any of these categories, let your midwife or obstetrician know early. More frequent urine screening and closer monitoring may be appropriate.

Can You Prevent a Kidney Infection During Pregnancy?

You cannot guarantee prevention, but several practical measures genuinely reduce your risk:

• Drink plenty of fluids — aim for six to eight glasses of water a day to keep urine flowing

• Don't hold in urine — empty your bladder regularly and fully

• Wipe front to back after using the toilet to prevent bacteria spreading from the bowel to the urethra

• Urinate after sex to flush out any bacteria introduced

• Attend all your antenatal urine screening appointments — catching asymptomatic bacteriuria early is your best protection

• Report any symptoms promptly — a lower UTI caught early is far easier to treat than one that has spread to the kidneys.

  
  

When to Seek Urgent Help

Go to your maternity assessment unit or A&E if you have:

• A temperature of 38°C or above that does not come down

• Severe one-sided back or flank pain

• Vomiting that prevents you keeping fluids down

• Signs of reduced fetal movement alongside any of the above

• Symptoms that are getting worse rather than better

  
  

What This Means for Your Pregnancy

What should you take away from all this information? That if you are diagnosed and treated quickly for a kidney infection during pregnancy you should have a positive outcome. Risks to yourself and the pregnancy increase if the infection is allowed to continue.

Does kidney infection cause miscarriage? Unfortunately, it’s not as simple as answering yes or no. An uncomplicated case of pyelonephritis that is diagnosed early on and treated with antibiotics is unlikely to be a cause of miscarriage in the first trimester. The risk lies in complications from an untreated infection, such as sepsis and premature labour.

Talk to your doctor if you have any concerns. If you are seeking expert obstetric care in London, myGynaePlus provides antenatal care and early pregnancy care as well as gynaecology services all in one place. This includes the type of comprehensive initial consultation that picks up urine infections before they become serious.

Frequently Asked Questions

1. Can a kidney infection in early pregnancy cause a miscarriage?

A kidney infection by itself is not a well-established direct cause of miscarriage. The main risk comes when the infection goes untreated and leads to sepsis. Prompt diagnosis and antibiotic treatment significantly reduce any risk to the pregnancy.

2. What are the warning signs of a kidney infection during pregnancy?

The key signs include a high fever (38°C or above), chills, one-sided back or flank pain, nausea, vomiting, and a burning sensation when urinating. If you notice these during pregnancy, contact your midwife or doctor the same day rather than waiting.

3. Is a UTI during pregnancy the same as a kidney infection?

No. A UTI typically refers to an infection of the bladder or urethra (lower urinary tract). A kidney infection (pyelonephritis) is more serious and occurs when bacteria travel upward to the kidneys. An untreated lower UTI can progress to a kidney infection.

4. How is a kidney infection treated when you're pregnant?

Most cases require hospitalisation, IV antibiotics, and fluids until symptoms improve, followed by oral antibiotics to complete a 14-day course. Certain antibiotics are safe in pregnancy, and your doctor will choose based on the bacteria identified and how far along you are.

5. Can kidney infection cause preterm labour?

Yes, this is a well-documented risk. Untreated or severe pyelonephritis is linked to preterm contractions and early delivery. Studies show that early treatment and follow-up suppressive antibiotic therapy can lower the rates of preterm birth associated with urinary infections in pregnancy.