What Are the Effects of a UTI in Pregnancy?

Approximately 8 percent of women develop urinary tract infections, or UTIs, during pregnancy, reported lead author John Dalzell, M.D., in “Urinary Tract Infections during Pregnancy,” published in the American Family Physician on February 1, 2000 12. Pregnancy increases the chance of UTIs because increased bladder volume and decreased tone allow urine to stagnate in the bladder, which promotes bacterial growth. UTIs during pregnancy can cause serious complications in both mother and fetus. Asymptomatic bacteriuria, which occurs in 6 to 10 percent of pregnant women, may not be detected until damage is done.

Preterm Labor

If left untreated, preterm labor and possibly premature delivery can occur. An infection caused by group B streptococcus may cause spontaneous premature rupture of membranes; group B causes around 5 percent of all UTIs in pregnancy, according to Delzell. A woman may not have any symptoms of a UTI even if she has bacteria in the urine and so may not seek medical treatment until contractions begin. Antibiotic treatment will cure UTI and should be instituted as soon as possible.


Pyelonephritis, a serious complication of UTI, occurs when infection travels upward from the bladder to the kidneys. Approximately 50 percent of women with a UTI develop pyelonephritis, Delzell reports. Symptoms of pyelonephritis include fever, flank pain and chills. Septicemia, a systemic infection can develop and threaten the life of mother and fetus. Pyelonephritis often requires intravenous antibiotic treatment in the hospital, according to Greenfield.

Fetal Effects

Even asymptomatic bacteriuria can cause fetal complications. Fetuses whose mothers have untreated or undiagnosed urinary tract infections are more likely to have low birth weights and intrauterine growth retardation, which means they’re smaller than most babies of the same gestational age, Delzell states. Babies may also develop pneumonia or group B streptococcal (GBS) infection right after birth if the urine contains GBS.

Other Maternal Effects