A randomized trial of three antibiotic regimens for the treatment of pyelonephritis in pregnancy

To compare the effectiveness of three antibiotic regimens for the treatment of acute pyelonephritis in pregnancy.

One hundred seventy-nine pregnant women earlier than 24 weeks' gestation who had acute pyelonephritis were randomized to 1) intravenous (i.v.) ampicillin and gentamicin, 2) i.v. cefazolin, or 3) intramuscular ceftriaxone. All participants then completed 10-day courses of oral cephalexin after primary treatment. A urine culture was performed on admission and 5-14 days after completion of therapy. Surveillance for persistent or recurrent infection and obstetric complications continued until delivery. On the basis of a two-sided hypothesis test and with alpha = .025, 60 subjects were needed in each group for statistical power greater than 80% to detect a difference between ceftriaxone and other antibiotics if hospital length of stay differed by 1 or more days.

The treatment groups were similar in age, parity, temperature, gestational age, and initial white blood cell count. There were no statistically significant differences in length of hospitalization, hours until becoming afebrile, days until resolution of costovertebral angle tenderness, or infecting organism. There were no statistically significant differences in birth outcomes between the three groups. The average (standard deviation) age at delivery was 38.8 +/- 3.6 weeks. The average birth weight was 3274 +/- 523 g. Eleven (6.9%) of 159 subjects delivered prematurely. Escherichia coli was the most common uropathogen isolated (137 of 179, 76.5%). Blood cultures were positive for organisms in 15 cases (8.4%). At follow-up examination within 2 weeks of initial therapy, eight (5.0%) of 159 subjects had urine cultures positive for organisms. Ten women (6.3%) had cultures positive for organisms later in their antepartum course, and 10 other participants (6.3%) developed recurrent pyelonephritis.

There are no significant differences in clinical response to antimicrobial therapy or birth outcomes among subjects treated with ampicillin and gentamicin, cefazolin, or ceftriaxone for acute pyelonephritis in pregnancy before 24 weeks' gestation.