Acute pyelonephritis in pregnancy.

OBJECTIVE: To examine the incidence of pyelonephritis and the incidence of risk factors, microbial pathogens, and obstetric complications in women with acute antepartum pyelonephritis.

METHODS: For 2 years, information on pregnant women with acute pyelonephritis was collected in a longitudinal study. All women were admitted to the hospital and treated with intravenous antimicrobial agents. We compared the pregnancy outcomes of these women with those of the general obstetric population received at our hospital during the same time period.

RESULTS: Four hundred forty cases of acute antepartum pyelonephritis were identified during the study period (incidence 1.4%). Although there were no significant differences in ethnicity, pyelonephritis was associated with nulliparity (44% versus 37%, P = .003) and young age (P = .003). Thirteen percent of the women had a known risk factor for pyelonephritis. Acute pyelonephritis occurred more often in the second trimester (53%), and the predominant uropathogens were Escherichia coli (70%) and gram-positive organisms, including group B beta Streptococcus (10%). Complications included anemia (23%), septicemia (17%), transient renal dysfunction (2%), and pulmonary insufficiency (7%).

CONCLUSION: The incidence of pyelonephritis has remained low in the era of routine prenatal screening for asymptomatic bacteriuria. First-trimester pyelonephritis accounts for over 1 in 5 antepartum cases. Gram-positive uropathogens are found more commonly as pregnancy progresses. Maternal complications continue, but poor obstetrical outcomes are rare.