What are the benefits of routinely screening for bacteria in the urine of pregnant women?

Photo of a pregnant woman at the hospital (PantherMedia / Iakov Filimonov)

It’s not clear whether it’s a good idea to routinely screen for bacteria in the urine of pregnant women (bacteriuria screening). It’s also not possible to say whether antibiotics should be used if high levels of bacteria are detected in the urine but there are no noticeable urinary tract problems.

Routine screening tests are carried out during pregnancy to see whether the baby is developing normally and the mother is healthy. Screening tests in pregnancy include ultrasound scans and blood tests, as well as urine tests. In Germany, special guidelines (“Mutterschafts-Richtlinien”) specify what is to be tested in pregnancy, and what sorts of tests are used.

Urine tests during pregnancy

These guidelines specify that pregnant women should have routine urine tests. The urine is tested for proteins, sugar and bacteria. Routine testing for bacteria is also referred to as bacteriuria screening. If high levels of bacteria are detected in the urine, additional testing is done to confirm the results.

Laboratory results show that about 2 to 15 out of 100 pregnant women have above-average levels of bacteria in their urine, but the bacteria aren’t causing any symptoms. This is called “asymptomatic bacteriuria.”

Urinary tract infections and possible consequences

Having bacteria in your urine doesn’t often cause any problems. The bacteria usually just go away after a while. But women who have bacteria in their urine might go on to develop a urinary tract infection (UTI) such as cystitis.

Hormonal and physical changes make pregnant women more susceptible to urinary tract infections. These arise if bacteria infect the urethra (the tube that urine flows out of) and bladder. If the germs move upwards, they may also infect the ureters or kidneys.

Typical signs of a lower urinary tract infection include the following:

  • Increased urge to urinate
  • Painful urination

The following symptoms may also appear if the ureters or the renal pelvis are infected:

  • Fever
  • Pain around the kidneys (flank pain)
  • In some cases, nausea and vomiting

If you have at least one of these symptoms, it is important to see your doctor.

In rare cases, untreated urinary tract infections during pregnancy may lead to serious problems such as septicemia (blood poisoning). The presence of bacteria in urine is also associated with a higher risk of premature birth and low birth weight.

Pregnant women who have bacteria in their urine are usually given antibiotics to prevent possible complications – even if they don’t have any symptoms.

Research in this area

Researchers from the Institute for Quality and Efficiency in Health Care (IQWiG, Germany) wanted to find out whether routine testing for bacteria in urine during pregnancy actually has any benefits for the mother or the child. But the IQWiG researchers didn’t find any suitable studies on the benefits of these tests. So instead, they looked into the advantages and disadvantages of antibiotics in the treatment of asymptomatic bacteriuria: Do the antibiotics help to prevent complications in the mother and child if bacteria are found in urine but there are no symptoms of a urinary tract infection? They found three suitable studies on this topic. The women who participated in the studies either took antibiotics, a placebo medication (fake treatment) or didn’t have any treatment.

Not clear whether testing for bacteria in urine during pregnancy has benefits

But the researchers weren’t able to draw any conclusions about whether taking antibiotics to treat asymptomatic bacteriuria has any advantages or disadvantages. The studies didn’t provide important information about the study participants and the possible side effects of the antibiotics. Also, the medicines used in the studies are no longer used nowadays. The studies were done in the 1960s, and their results can’t be directly applied to the current health care situation for pregnant women.

So it’s still not clear whether it makes sense to routinely screen for bacteria in urine during pregnancy. It’s also not clear whether pregnant women should take antibiotics if bacteria are found in their urine but they don’t have any symptoms.