Are Water Infections Common in Early Pregnancy?

You feel a burning sensation when you wee. You need to rush to the toilet more often than usual. Your lower abdomen feels uncomfortable. Sound familiar?

Water infections, or urinary tract infections (UTIs) as they are clinically known, are one of the most common health concerns women raise during early pregnancy. You are not imagining the increase in symptoms, and you are far from alone in dealing with them. Pregnancy genuinely raises your risk of getting a water infection, and the first trimester is when that risk begins.

Here is everything you need to know, clearly explained.

What Is a Water Infection?

A water infection is the everyday UK term for a urinary tract infection. It occurs when bacteria enter the urinary tract and multiply. The urinary tract includes the urethra (the tube through which you urinate), the bladder, the ureters (tubes connecting bladder to kidneys), and the kidneys themselves.

Most water infections affect the lower urinary tract, specifically the bladder. This is known as cystitis. When infection travels upward to the kidneys, it becomes a more serious condition called pyelonephritis.

The most common culprit behind water infections is Escherichia coli (E. coli), a bacterium found normally in the gut. Around 80 to 90% of UTIs during pregnancy are caused by E. coli, according to StatPearls via the National Institutes of Health. Other bacteria that can cause infections during pregnancy include Group B Streptococcus (GBS), Klebsiella pneumoniae, and Proteus mirabilis.

How Common Are Water Infections in Early Pregnancy?

Very common. Water infections are, in fact, the most frequent bacterial infection to occur during pregnancy.

Around 1 in 10 pregnant women develop a UTI at some point, according to Pregnancy Birth and Baby, a service backed by the Australian Government. In the UK, nearly 189,756 hospital admissions in 2023 to 2024 were linked to UTIs overall, as recorded by the UK Health Security Agency (UKHSA).

But the full picture is even bigger than symptomatic infections suggest. A condition called asymptomatic bacteriuria, where bacteria are present in the urine without causing any noticeable symptoms, affects 2 to 10% of pregnant women. The Children's Hospital of Philadelphia puts the figure at 5 to 10% for this silent infection. You feel completely well, but bacteria are quietly multiplying in your urinary tract.

This is why your midwife or GP asks for a urine sample at your first antenatal appointment, even when you have no symptoms at all.

Why Does Early Pregnancy Increase the Risk?

Let's break it down. Several physical changes happen in your body from the moment you conceive that make the urinary tract more vulnerable to infection.

Progesterone relaxes the muscles of the urinary tract. Progesterone, which rises sharply in early pregnancy, relaxes smooth muscle throughout the body, including the ureters. This slows the flow of urine, allowing bacteria more time to establish themselves. According to Medscape's clinical review, ureteral dilation begins by around 10 weeks of pregnancy and increases throughout gestation.

Urine composition changes. During pregnancy, your urine becomes less acidic. It also contains higher levels of glucose, protein, and hormones. Bacteria thrive in this altered environment far more easily than in normal urine.

The bladder does not empty as fully. Hormonal changes reduce bladder tone and capacity. The growing uterus also puts pressure on the bladder, meaning residual urine is more likely to sit in the bladder after urinating. Bacteria have more opportunity to multiply in retained urine.

Partial immune suppression. To protect the developing baby from being treated as a foreign body, the immune system is partially suppressed during pregnancy. This means your body is less effective at fighting off bacterial invasion before it takes hold.

The risk increases from around 6 weeks. Research published via Medscape shows that the general risk of UTI in pregnancy rises from about 6 weeks of gestation and peaks between 22 and 24 weeks. The first trimester is when silent infections are most likely to begin.

Symptoms of a Water Infection in Early Pregnancy

Some water infections in pregnancy produce no symptoms at all. Others come on quickly with clear signs. Here is what to look out for:

Common symptoms of a bladder infection (cystitis):

• Burning or stinging when you urinate

• Needing to wee more frequently than usual

• A strong, sudden urge to urinate with little coming out

• Cloudy urine

• Urine that smells noticeably strong or unpleasant

• Blood in the urine (pink or red tinged)

• Discomfort or pressure in the lower abdomen, above the pubic bone

• Mild pelvic aching

Symptoms that suggest the infection may have spread to the kidneys:

• Fever above 37.5°C, with or without chills and shaking

• Pain in your back or sides (flank pain), below the ribs

• Nausea or vomiting alongside urinary symptoms

• Feeling very unwell generally

The challenge during early pregnancy is that some of these symptoms, particularly frequent urination and mild lower abdominal discomfort, can feel exactly like normal pregnancy changes. This makes it easy to dismiss a water infection as just part of being pregnant. If you are at all uncertain, get tested. A simple urine test removes any doubt.

Why Water Infections Need Prompt Treatment in Pregnancy

Left untreated, a water infection in pregnancy is not just an inconvenience. It carries real risks.

Progression to kidney infection. An untreated bladder infection can travel upward to the kidneys. Pyelonephritis (kidney infection) is one of the most common reasons for hospital admission during pregnancy, according to ACOG (American College of Obstetricians and Gynecologists). Once an infection reaches the kidneys, it becomes a serious systemic illness.

Preterm labour. Bacterial infections can trigger uterine contractions. Research published in BMC Pregnancy and Childbirth via PubMed Central found that women with a UTI during pregnancy had significantly more preterm deliveries than those without. Tommy's, the UK pregnancy charity, also confirms that untreated UTI infections can bring on premature labour.

Sepsis risk. If bacteria enter the bloodstream from a kidney infection, sepsis can develop. This is a life-threatening emergency that requires immediate hospital treatment.

Asymptomatic bacteriuria and pre-eclampsia. Some research links untreated asymptomatic bacteriuria with a higher risk of pre-eclampsia, a serious pregnancy condition involving high blood pressure. This reinforces why routine urine screening in early pregnancy is not just routine box-ticking but genuinely protective.

How a Water Infection Is Diagnosed During Pregnancy

Diagnosis is straightforward. Here is how it works:

Routine screening at your booking appointment. In UK antenatal care, all pregnant women are asked to provide a urine sample at their first appointment. This screens for both symptomatic and asymptomatic infections. Catching bacteria early, before any symptoms develop, prevents the infection from progressing.

Urinalysis. A urine dipstick test checks for white blood cells, red blood cells, nitrites, and protein. Results are available quickly in the clinic and can indicate whether infection is likely.

Urine culture. A midstream urine (MSU) sample is sent to a laboratory to identify the specific bacteria causing the infection and test which antibiotics it responds to. Results take 24 to 48 hours but allow your doctor to prescribe the most appropriate antibiotic.

If you develop symptoms between antenatal appointments, contact your GP, midwife, or call NHS 111. Do not wait for your next scheduled visit.

Treatment for Water Infections in Early Pregnancy

Water infections in pregnancy are treated with antibiotics. The type of antibiotic prescribed depends on the trimester you are in, the bacteria identified in your urine culture, and your individual medical history.

Safe antibiotics commonly used during pregnancy include:

• Cefalexin (cephalexin): A cephalosporin antibiotic widely considered safe throughout pregnancy. It is a common first-line choice across UK antenatal guidelines.

• Amoxicillin: Safe in pregnancy if the bacteria are confirmed to be susceptible. Not used as a first empiric choice because E. coli resistance rates to amoxicillin are high.

• Nitrofurantoin: Effective against many common pathogens and frequently prescribed. There is some mixed data on use in the very first trimester, so your doctor will weigh this against available alternatives. Nitrofurantoin should not be used near the end of pregnancy (from 36 weeks) due to risks to the newborn.

• Trimethoprim: Avoided in the first trimester because it acts as a folic acid antagonist, which carries theoretical risks during early foetal development. Commonly used from the second trimester onwards.

Antibiotics to avoid during pregnancy:

Your doctor will not prescribe certain antibiotics that are otherwise commonly used for water infections outside pregnancy. These include fluoroquinolones (such as ciprofloxacin), which are linked to effects on developing cartilage, and tetracyclines, which affect foetal teeth and bone development.

NHS Scotland's Right Decisions clinical guidance lists nitrofurantoin (100mg modified-release twice daily for 7 days) as a first-line treatment for UTI in pregnancy, with cefalexin as a second-line option.

The full course of antibiotics, usually 7 days, must be completed even if symptoms improve before the course ends. Stopping early risks the infection returning or bacteria developing resistance.

A repeat urine test one to two weeks after completing treatment is standard practice to confirm the infection has cleared.

When to Seek Help Immediately

Some symptoms should not wait for a routine GP appointment. Contact your midwife, GP, or call NHS 111 straight away if you experience:

• A temperature above 37.5°C during pregnancy

• Back or flank pain alongside urinary symptoms

• Nausea and vomiting with urinary discomfort

• Blood in your urine

• Feeling severely unwell, confused, or shivery

These can indicate the infection has spread to the kidneys, or in rare cases suggest sepsis. Tommy advises contacting your GP urgently or calling NHS 111 if you have a high temperature, feel hot and shivery, or have back pain alongside urinary symptoms during pregnancy.

If symptoms are very severe, go to A&E.

Preventing Water Infections During Pregnancy

You cannot remove every risk, but these practical steps genuinely reduce the likelihood of developing a water infection:

• Drink plenty of water. Aim for 6 to 8 glasses a day. Staying well-hydrated keeps urine diluted and flushes bacteria from the urinary tract more regularly.

• Do not hold on when you need to go. Empty your bladder fully and as soon as you feel the urge. Holding on allows bacteria more time to multiply.

• Wipe front to back. This prevents bacteria from the bowel area travelling toward the urethra.

• Urinate before and after sex. Sexual activity can push bacteria closer to the urethra.

• Avoid scented soaps and products around the vaginal area. These can disrupt the natural bacterial balance and irritate the urethra.

• Wear breathable cotton underwear. Synthetic fabrics trap moisture, which helps bacteria thrive.

• Attend all antenatal urine screenings. Routine tests catch silent infections before they become symptomatic.

If you have had recurrent water infections before or during a previous pregnancy, tell your midwife at your first appointment. Women with a history of UTIs, diabetes, sickle cell trait, or structural urinary tract abnormalities are at higher risk and may need more frequent urine monitoring throughout pregnancy.

Getting Support at myGynaePlus

If you are experiencing urinary symptoms during pregnancy and are not sure what to do, getting professional assessment quickly matters. The team at myGynaePlus, based in West London, offers specialist antenatal care, obstetric consultations, and expert gynaecological assessments. Whether you need a urine screen, early pregnancy care, or have ongoing concerns about infections in pregnancy, the clinic provides women-focused care from specialist clinicians.

You can book an appointment directly at their website.

Frequently Asked Questions

Can a water infection in early pregnancy harm the baby?

A water infection treated promptly is very unlikely to harm your baby. The risk comes when infections are left untreated. An untreated bladder infection can progress to a kidney infection, which is associated with preterm labour and low birth weight. This is why getting tested and starting antibiotics quickly is so important. Most women who treat their water infection promptly have no lasting complications.

How do I know if my frequent urination is a water infection or just early pregnancy?

Frequent urination is normal in early pregnancy due to hormonal changes and increased kidney activity. The key difference is whether urinating is painful or uncomfortable. Normal pregnancy urination does not hurt. If you feel a burning or stinging sensation when you wee, notice cloudy or strong-smelling urine, or have lower abdominal pressure that goes beyond mild bloating, these point toward a water infection rather than typical pregnancy changes.

Can I treat a water infection during pregnancy without antibiotics?

No. During pregnancy, water infections must be treated with antibiotics prescribed by a doctor. Home remedies or waiting to see if the infection clears are not safe options when you are pregnant. Even a silent infection with no symptoms needs antibiotic treatment to prevent progression. Drinking plenty of water helps support recovery but cannot clear an established bacterial infection on its own.

Will I be tested for water infections throughout my entire pregnancy?

You will have a urine test at your booking appointment. If that comes back clear, further testing is typically guided by symptoms you report. Some women with risk factors, such as a history of UTIs, diabetes, or a previous kidney infection in pregnancy, may have repeat urine cultures at later antenatal appointments. If you develop any symptoms at any stage of pregnancy, always request a test regardless of when you were last screened.

Can a water infection cause a miscarriage?

A water infection itself does not directly cause miscarriage. The concern is what happens when infections are left untreated and spread. An untreated kidney infection can cause serious systemic illness during pregnancy. Prompt treatment of any urinary infection during the first trimester, or at any stage of pregnancy, significantly reduces any risk to the pregnancy. If you are in early pregnancy and develop any fever or urinary symptoms, get assessed the same day rather than waiting.