Urinary tract infections are common during pregnancy, probably because the enlarging uterus and hormones slow the flow of urine in the tubes that connect the kidneys to the bladder (ureters). When urine flow is slow, bacteria may not be flushed out of the urinary tract, increasing the risk of an infection.
Urinary tract infections increase the risk of preterm labor and premature rupture of the membranes containing the fetus. Sometimes an infection in the bladder or ureters spreads up the urinary tract and reaches a kidney, causing an infection there (see see Bladder and Kidney Infections). Bacteria may infect the urine without causing symptoms of urinary tract infections, so doctors usually check the urine for bacteria even in pregnant women without symptoms.
Treatment consists of antibiotics. Doctors choose antibiotics that do not harm the fetus, such as cephalexin, nitrofurantoin, or trimethoprim/sulfamethoxazole. Women who have had more than one bladder infection or have had a kidney infection need to take antibiotics throughout pregnancy to prevent subsequent urinary tract infections.
Last full review/revision September 2013 by Lara A. Friel, MD, PhD