What is Urinary Tract Infection During Pregnancy?
Urinary tract infection (UTI) is one of the most frequently encountered conditions in pregnant women. The incidence of UTI in pregnancy is comparable to the general population (approximately 3-10%). However, it is associated with significant complications both to the mother and the baby when it occurs during pregnancy. It is therefore important that the condition be recognized and treated promptly.(2✔)
During pregnancy there are changes that occur in the woman’s urinary tract that increase the risk of UTI. These are as follows:
- Dilatation of the ureter combined with decreased tone permits back flow of urine from the bladder to the ureter. This is referred to as vesico-ureteral reflux (VUR).
- Size of the urinary bladder is increased, which is combined with a decreased tone in the bladder. This causes stasis of urine in the bladder and occurrence of vesico-ureteric reflux (VUR).
- Urine of a pregnant woman may contain increased amounts of glucose which contribute to the bacterial growth.
- Increased excretion of hormonal products and amino acids in the urine increases urinary pH which is normally acidic. This promotes the growth of certain bacteria such as Escherichia coli (E. coli).
- Pressure on the bladder and the ureter due to the increase in size also causes stasis of urine, a factor that encourages bacterial growth and multiplication.
Therefore the two major factors that increase the risk of UTI during pregnancy are stasis of urine and vesico-ureteric reflux.
Studies have shown that many women have asymptomatic urinary infection (asymptomatic bacteriuria) with presence of bacteria in the urine in the absence of symptoms, even before pregnancy, which may become overt during pregnancy. The risk factors of urinary tract infection in women in general include the following -
- History of diabetes mellitus
- Increased age
- Frequent antibiotic use – eliminates Lactobacilli in the vagina which normally prevents E. coli overgrowth
- Poor genital hygiene
- Lower socioeconomic status
- Shorter urethra through which bacteria in the genital skin area easily gain access into the urinary tract
- Increased sexual activity
- Multiple earlier pregnancies
The organisms commonly associated with UTI include -
- E. coli (60-80%)
- Coagulase negative staphylococcus (CoNS)
- Staphlococcus aureus
- Group B streptococcus (GBS)
Less common organisms include -
- Gardenella vaginalis
- and Ureaplasma urealyticum
Urinary tract infections during pregnancy can significantly harm both the mother and the baby. The woman may have asymptomatic bacteriuria or symptomatic urinary tract infection both of which can affect the baby.
- Asymptomatic bacteriuria has been associated with an increased incidence of decreased growth of the fetus in the womb or intra-uterine growth retardation (IUGR) and low birth weight.
- Symptomatic UTI has been found to be associated with an increased incidence of premature rupture of membranes and pre-term labor.
The incidence of complications both in the mother and the fetus due to UTI necessitates screening of the pregnant woman for presence of bacteria (bacteriuria) in the urine routinely.
The clinical features of urinary tract infection depend on whether the infection is in the lower urinary tract (bladder) or higher up in the kidney.(3✔)
Bladder or lower UTI (cystitis)
- Burning pain during urination (dysuria) – this is the most important symptom suggestive of UTI since the other symptoms may occur in most pregnant women and are hence maybe non-specific.
- Frequent urination
- Urgency or a feeling to pass urine urgently
- Lower abdominal pain and discomfort
- Frequent urination during the night (nocturia)
- Passage of cloudy urine
- Occasionally associated with passing of blood in the urine (hematuria)
Kidney or upper urinary tract infection (pyelonephritis)
- Fever with shaking chills
- Loin pain and tenderness on examination
- Loss of appetite
- Nausea and vomiting
Complications in the mother due to severe UTI include kidney dysfunction, pre-term labor, lung damage and respiratory distress syndrome and rarely septic shock.
The diagnosis of UTI during pregnancy is often made based on history and physical examination and it is then confirmed by a urine analysis.(4✔)
History and Physical Examination - Often a history of burning pain during urination is highly suggestive of a UTI.
- Nitrites in urine using dipstick – This is a simple inexpensive and easy to perform test to diagnose urinary tract infection. A positive nitrites test indicates presence of bacteria in the urine and may warrant further tests such as urine culture.
- Urine microscopy – A sample of urine is centrifuged and the sediment examined under the microscope for abnormal findings such as the presence of increased number of leukocytes (white blood cells), red blood cells and occurrence of urinary casts.
Presence of increased leukocytes (pus cells) associated with red blood cells indicates urinary infection. Presence of urinary casts indicates involvement of kidneys.
- Urine culture and sensitivity – Before giving a urine sample for culture, the genital area should be washed and wiped dry to avoid contamination. A mid-stream sample should be given i.e., allowing the initial portion of urine to be passed and then collecting the sample in the culture bottle provided. It is best to collect the urine sample immediately after a shower or after washing the genitalia (this avoids any contamination of the sample from skin flora).
The urine will be streaked on special culture media which are observed for bacterial growth. This normally takes 48 hours to report.
In the absence of symptoms, two consecutive voided samples with isolation of the same bacterial strain, showing a colony count of 100,000 colony-forming units (CFUs) per ml or more is considered a positive result. In the presence of symptoms of UTI or a sample collected from a catheter, a colony count of that is less than 100,000 CFUs /ml is also diagnostic.
In a normally collected sample a colony count of less than 100,000 CFUs /ml and presence of two or more organisms suggests contamination and possible improperly collected sample. If there is doubt the test may be repeated.
Blood Tests – Normally, blood tests may not be necessary for lower urinary infection however if kidney involvement is suspected, then kidney function tests such as blood urea and serum creatinine are done to assess the kidney function.
Imaging Tests – In suspected kidney involvement, an ultrasound of the kidney may reveal enlarged kidneys (hydronephrosis) or presence of stones in the urinary tract. Usually if kidney ultrasound is inconclusive, a specialized test called Intravenous Urogram (IVU) may be considered but this means some potential risk of increased risk of radiation to the fetus. A quick 3 film IVU can be done to minimize the radiation. The actual risks need to be discussed with the mother. This test during the first trimester should not be considered. Obstruction of the urinary tract by a stone can result in stasis of urine and cause UTI.
More recently a plain CT of the Kidney, Ureter and bladder region maybe preferred to the IVU as it is quick and does not involve any contrast medium to be injected however again due to radiation risk this is best avoided.
MRI – maybe used rarely in 2nd or 3rd Trimester to rule out obstruction of the kidneys.
Guidelines for Imaging during pregnancy
The general guidelines for imaging in pregnancy from the American College of Obstetricians and Gynecologists are as follows -
For Ultrasound imaging - “There have been no reports of documented adverse fetal effects for diagnostic ultrasound procedures, including duplex Doppler imaging.” “There are no contraindications to ultrasound procedures during pregnancy, and this modality has largely replaced x-ray as the primary method of fetal imaging during pregnancy.”
For X-rays - “Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Specifically, exposure to less than 5 RAD has not been associated with an increase in fetal anomalies or pregnancy loss.”
Magnetic resonance imaging -“Although there have been no documented adverse fetal effects reported, the National Radiological Protection Board arbitrarily advises against its use in the first trimester.”
A plain Abdominal x-ray exposes to only 0.245 RAD whereas an Intravenous urogram exposes to 1.398 RAD – hence both are generally safe.
It is important to promptly diagnose and treat UTI during pregnancy to avoid complications to the mother and the baby.
Treatment of asymptomatic bacteriuria (ASB) and lower UTI (cystitis)
The management of asymptomatic bacteriuria and cystitis include the following:
Administration of appropriate antibiotics – Following a urine culture and antibiotic sensitivity testing, appropriate antibiotics to which the organism is sensitive should be administered. Antibiotics commonly employed during pregnancy include -
- Cephalexin 500 mg, 4 times daily
- Ampicillin 500 mg, 4 times daily
In E. coli infections the incidence of resistance to Ampicillin and Amoxycillin is high and these agents are not used. Fosfomycin, a phosphonic acid derivative, is another useful agent in the treatment of uncomplicated UTIs caused by E. coli and Enterococci.
Antibiotics to avoid during pregnancy -
- Ciprofloxacin – 1st Trimester
- Nitrofurantoin – 3rd Trimester
- Sulphamethoxazole – 1st & 3rd Trimester of pregnancy
- Trimethoprim -1st & 3rd Trimester of pregnancy
Fluid replacement – If the patient is dehydrated, IV fluid replacement may be necessary.
Follow-up urine culture – All pregnant women with UTI should undergo periodic screening of urine for culture since recurrent infections can occur.
In some women, in spite of treatment, bacteriuria persists due to various reasons such as diabetes, poor immunity, sickle cell disease or a history of recurrent UTI even before pregnancy. Such women should be administered prophylactic antibiotics throughout pregnancy to prevent complications to both mother and the fetus.
Treatment of Pyelonephritis
Pyelonephritis usually occurs later in pregnancy at the end of the second and third trimesters. Treatment includes admission to hospital and(6✔)
- Administration of intravenous antibiotics such as Cephalosporin and Gentamicin
- IV fluid replacement may be needed but should be done with caution
- Acetaminophen for reducing fever
- Anti-emetics such as Metoclopramide for nausea and vomiting
It should be remembered that during pregnancy the use of certain antibiotics is contraindicated because they can harm the fetus. These include Tetracyclines, Chloramphenicol and Trimethoprim. Fluoroquinolones should be used with caution.
It is important to prevent UTI during pregnancy and avoid fetal as well as maternal complications.
Urine screening for bacteria
Routine screening for the presence of clinically significant bacteriuria in all pregnant women should be done. The most reliable method of diagnosing presence of bacteria in the urine is urine culture. Therefore a routine urine culture and sensitivity is recommended during the first antenatal visit and again during the third trimester.(7✔)
If asymptomatic bacteriuria is found to occur, the recommended treatment guidelines given above have to be followed.
Some general measures followed routinely could prevent or reduce the incidence of UTIs.
- Avoid bathtubs
- Wash hands after using the toilet
- Clean the genital area with washed clothes
- Wipe from front-to-back after passing urine or stools
- Use liquid soap to prevent colonization from bar soap
- Urinary Tract Infections During Pregnancy - (http://www.aafp.org/afp/2000/0201/p713.html)
- Urinary tract infections in pregnancy: old and new unresolved diagnostic and therapeutic problems - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4379362/)
- Urinary Tract Infections - (https://www.kidney.org/atoz/content/uti)
- Urinary Tract Infection During Pregnancy: Symptoms & Prevention - (https://americanpregnancy.org/pregnancy-complications/urinary-tract-infections-during-pregnancy/)
- The Diagnosis of Urinary Tract Infection - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2883276/)
- Recommendations on screening for asymptomatic bacteriuria in pregnancy - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6041243/)
- Diagnosis and Treatment of Acute Pyelonephritis in Women - (https://www.aafp.org/afp/2011/0901/p519.html)
Latest Publications and Research on Urinary Tract Infection During Pregnancy
- [Asymptomatic bacteriuria in pregnancy]. - Published by PubMed
- Vaginal delivery is safely achieved in pregnancies complicated by spinal cord injury: a retrospective 25-year observational study of pregnancy outcomes in a national spinal injuries centre. - Published by PubMed
- Determinants of preterm birth among mothers who gave birth in East Africa: systematic review and meta-analysis. - Published by PubMed
- Hyperprogression after immunotherapy: A comprehensive review. - Published by PubMed
- Urinary tract infections in pregnancy in a rural population of Bangladesh: population-based prevalence, risk factors, etiology, and antibiotic resistance. - Published by PubMed