A number of maternal bacterial infections are associated with preterm birth including pyelonephritis, asymptomatic bacteriuria, pneumonia, and appendicitis. A review into giving antibiotics in pregnancy for asymptomatic bacteriuria (urine infection with no symptoms) found the research was of very low quality but that it did suggest that taking antibiotics reduced the numbers of preterm births and babies with low birth weight.[68] Another review found that one dose of antibiotics did not seem as effective as a course of antibiotics but fewer women reported side effects from one dose.[69] This review recommended that more research is needed to discover the best way of treating asymptomatic bacteriuria.[68]