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Urine culture during pregnancy
Medical expert of the article
Last reviewed: 27.07.2025
In addition to the fact that pregnant women in the early stages must undergo examination (including taking all the necessary tests), laboratory testing of urine for the presence of bacteria (with determination of their type and quantity) - bacteriological or bacterial culture of urine during pregnancy - refers to tests that allow timely detection of problems with the bladder and urinary tract, which often occur in women during the period of bearing a child.
Indications for the procedure urine culture during pregnancy
It should be borne in mind that during pregnancy – due to hormonal and physiological changes – the urethra shortens (by about 3 cm); the ureter expands; under the pressure of the growing uterus, the volume of the bladder decreases; there may be stagnation of urine (due to compression of the ureter), leading to vesicoureteral reflux. The body's ability to resist infections also decreases, which is due to temporary physiological immunosuppression. All this together increases the likelihood of developing urinary tract infections.
Why do you need a urine culture during pregnancy? To detect microbes in the urine that can cause urinary tract infections - bladder, ureters, urethra, and kidneys.
First of all, indications for this laboratory test include the presence of symptoms of cystitis during pregnancy (frequent urge to urinate, burning during urination, etc.). See also - Cystitis during early pregnancy
The most significant factor predisposing women to urinary tract infections during pregnancy, experts believe, is asymptomatic bacteriuria, which affects up to 6-10% of pregnant women. This is when bacterial colonization of the urinary tract occurs, but the microorganisms do not manifest themselves for a long time.
If asymptomatic bacteriuria is not treated, the risk of activation of uropathogenic microorganisms with the development of urinary tract infections increases many times over, and, according to WHO, with asymptomatic bacteriuria, pyelonephritis develops in 45% of cases in pregnant women.
In addition, bacteriuria during pregnancy is associated with the risk of preterm birth and low birth weight infants. [ 1 ]
Preparation
For more information on how to properly take a urine culture during pregnancy, as well as how to collect a urine culture during pregnancy, read the publication - Bacterial Culture Analysis During Pregnancy
Technique urine culture during pregnancy
When performing urine culture in pregnant women, the technique of performing it - with seeding of biological material (i.e. urine) in a nutrient medium and keeping it for 24 hours at body temperature (so that the bacteria manifest themselves and can be identified using electron microscopy or mass spectrometry) - in any certified medical laboratory is similar to the technique of performing urine analysis for sterility. [ 2 ] And read more about this in the articles:
What does a urine culture show during pregnancy?
The doctor's interpretation of the results obtained from a bacteriological examination of urine provides objective data regarding the degree of infection of the urinary tract and specific pathogens causing the infection.
The colony forming unit (CFU/ml) is used to count the number of bacteria present in one milliliter of urine sample.
Until recently, urine was considered a sterile biological fluid, but after the American Society for Microbiology conference held in May 2021, this postulate was challenged.
If the threshold of 10-50 CFU/ml is not exceeded, then these are normal urine culture values. In the case of asymptomatic bacteriuria, a positive urine sample is determined at a level of 100 CFU/ml, and at ≥105 CFU/ml bacteriuria is considered significant. A similar level is also an indicator of urinary tract infection.
Thus, the presence of pathogenic bacteria in urine at a level of 100 CFU/ml is considered significant, and this is a positive culture, that is, a poor urine culture during pregnancy, requiring the appointment of adequate treatment with mandatory bacterial culture after its completion. [ 3 ]
Urine culture for Escherichia coli during pregnancy (performed during a general urine culture) is important for prescribing the correct treatment for infectious and inflammatory processes in the urinary tract, since it is most often caused by E. coli.
Also, enterobacteria Escherichia coli colonize the urinary tract in asymptomatic bacteriuria. In addition, in this condition, enterococci Enterococcus faecalis can be detected in urine culture during pregnancy; group B streptococci (Streptococcus agalactiae); pseudomonads (Pseudomonas aeruginosa), Proteus (Proteus mirabilis) and Klebsiella (Klebsiella pneumonia); staphylococci (Staphylococcus saprophytics, Staphylococcus epidermidis).
Streptococcus is detected in urine culture during pregnancy much less frequently than Escherichia coli. In most cases, it is commensal streptococcus of serogroup B – Streptococcus agalactiae, the prevalence of which among women in the form of asymptomatic carriage (as part of the normal microbiota of the gastrointestinal and genitourinary tracts) is estimated at approximately 50%.
During pregnancy, these bacteria can spread both in utero (ascending route) and during childbirth – through neonatal aspiration of infected amniotic fluid (with the risk of developing pneumonia, meningitis or sepsis in the newborn).
In addition, carriage of streptococcal infection can lead to the development of chronic glomerulonephritis during pregnancy, which, in turn, causes maternal renal failure, delayed prenatal development of the fetus, and premature birth.
Bacteriological examination, as in the case of other microorganisms, includes urine culture for staphylococcus during pregnancy. In particular, detection of Staphylococcus saprophytics can be both in acute cystitis and in cases of asymptomatic bacteriuria. But Staphylococcus aureus is a very rare cause of urinary tract infection, and its isolation in a urine sample is usually secondary to staphylococcal bacteremia. [ 4 ]
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