(See also Urinary Tract Infections (UTI).)

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 preterm labor and premature rupture of the membranes.

Diagnosis

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

Treatment

• 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 2: Drugs in Pregnancy: 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

After treatment, proof-of-cure cultures are required. Women who have pyelonephritis or have had > 1 UTI may require suppressive therapy, usually with trimethoprim/sulfamethoxazole (before 34 wk) or nitrofurantoin, for the rest of the pregnancy. In women who have bacteriuria with or without UTI or pyelonephritis, urine should be cultured monthly.

Last full review/revision December 2008 by Sean C. Blackwell, MD