Among the many changes that take place in the body during pregnancy is an increase in the risk of developing an infection of the urinary tract. The hormonal changes as well as the physical changes exerted by the enlarging uterus can lead to a slowdown of the passage of urine through the urinary tract and even to vesicouteral reflux, a condition in which urine in the bladder backs up, or refluxes, back into the ureters (the tubes that carry urine from the kidneys to the bladder). The hormone progesterone is responsible for changes in action of the smooth muscle walls of the ureters, and the weight of the uterus itself can lead to urinary retention. There is further an expansion of blood volume and increased load on the kidneys in pregnant women, resulting in increased urine output in the face of decreased mobility of the ureters. Finally, pregnant women tend to have higher urinary levels of glucose than nonpregnant women. All of these changes predispose to infection within the urinary tract.
As in nonpregnant women, urinary infections can occur in the urethra or bladder or may spread to the kidneys (pyelonephritis). The majority of infections come from existing bacteria in the vaginal and anal areas that spread upward (also termed retrograde) through the urinary system.
Fortunately, urinary infections in pregnancy are readily treatable. Even though pregnant women may be concerned about taking prescription medications, there are a number of antibiotics that are effective in treating kidney and urinary tract infections that are known to be safe for both mother and baby. Cephalexin, ampicillin, and nitrofurantoin are examples of antibiotics that may be used to treat lower urinary tract infections and cystitis in pregnant women. These medications are taken in pill or tablet form.
Infections of the kidney (pyelonephritis) require more intensive treatment with hospitalization and intravenous antibiotics. Antibiotics of the cephalosporin class or gentamycin may be safely used. If fever is present, acetaminophen (Tylenol) may be used, and there are a number of antiemetic drugs that are safe for pregnant women to take if nausea and vomiting accompany the infection.
The prognosis is excellent for most cases of urinary infection in pregnancy. Spread of the infection to the fetus is rare. As with any illness, it is important for the mother to maintain adequate hydration to avoid reducing blood flow to the uterus during a urinary tract infection. If pyelonephritis (kidney infection) goes untreated, maternal and fetal complications may develop including premature labor and low birth weight, so it is important to seek medical care when symptoms of a urinary infection are present. Pregnant women should not wait until the urinary tract infection becomes “worse” or rely on alternative treatments to “treat” an infection; they should call their doctor as soon as symptoms occur.