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Urinary Tract Infection in Pregnancy


Lara A. Friel

, MD, PhD, University of Texas Health Medical School at Houston, McGovern Medical School

Last full review/revision Jun 2021| Content last modified Jun 2021
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Urinary tract infection (UTI) is common during pregnancy, apparently because of urinary stasis, which results from hormonal ureteral dilation, hormonal ureteral hypoperistalsis, and pressure of the expanding uterus against the ureters. Asymptomatic bacteriuria occurs in about 15% of pregnancies and sometimes progresses to symptomatic cystitis or pyelonephritis. Frank UTI is not always preceded by asymptomatic bacteriuria.

Asymptomatic bacteriuria, UTI, and pyelonephritis increase risk of

Diagnosis of UTI in Pregnancy

  • Urinalysis and culture

Urinalysis and culture are routinely done at initial evaluation to check for asymptomatic bacteriuria. Diagnosis of symptomatic UTI is not changed by pregnancy.

Treatment of UTI in Pregnancy

  • Antibacterial drugs such as cephalexin, nitrofurantoin, or trimethoprim/sulfamethoxazole

  • Proof-of-cure cultures and sometimes suppressive therapy

Treatment of symptomatic UTI is not changed by pregnancy, except drugs that may harm the fetus are avoided (see table Some Drugs With Adverse Effects During Pregnancy). Because asymptomatic bacteriuria may lead to pyelonephritis, it should be treated with antibiotics similar to an acute UTI.

Antibacterial drug selection is based on individual and local susceptibility and resistance patterns, but good initial empiric choices include the following:

  • Cephalexin

  • Nitrofurantoin

  • Trimethoprim/sulfamethoxazole

Nitrofurantoin is contraindicated in pregnant patients at term, during labor and delivery, or when the onset of labor is imminent because hemolytic anemia in the neonate is possible. Pregnant women with G6PD (glucose-6-phosphate dehydrogenase) deficiency should not take nitrofurantoin. Incidence of neonatal jaundice is increased when pregnant women take nitrofurantoin during the last 30 days of pregnancy. Nitrofurantoin should be used during the 1st trimester only when no other alternatives are available.

Trimethoprim/sulfamethoxazole (TMP/SMX) can cause congenital malformations (eg, neural tube defects) and kernicterus in the neonate. Folic acid supplementation may decrease the risk of some congenital malformations. TMP/SMX should be used during the 1st trimester only when no other alternatives are available.

After treatment, proof-of-cure cultures are required.

Women who have pyelonephritis or have had more than one UTI may require suppressive therapy, usually with TMP/SMX (before 34 weeks) or nitrofurantoin, for the rest of the pregnancy.

In women who have bacteriuria with or without UTI or pyelonephritis, urine should be cultured monthly.

Key Points

  • Asymptomatic bacteriuria, UTI, and pyelonephritis increase risk of preterm labor and premature rupture of the membranes.

  • Initially treat with cephalexin, nitrofurantoin, or trimethoprim/sulfamethoxazole.

  • Obtain proof-of-cure cultures after treatment.

  • For women who have had pyelonephritis or more than one UTI, consider suppressive therapy, usually with trimethoprim/sulfamethoxazole (before 34 weeks) or nitrofurantoin.

Drugs Mentioned In This Article

Drug Name Select Trade
No US brand name
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