INTRAUTERINE INFECTION AND PRETERM DELIVERY

From the Department of Obstetrics and Gynecology and the Center for Research on Women’s Health, University of Alabama at Birmingham, Birmingham. Address reprint requests to Dr. Goldenberg at the Department of Obstetrics and Gynecology, University of Alabama at Birmingham, 618 S. 20th St., OHB 560, Birmingham, AL 35233-7333, or at rlg@uab.edu. ©2000, Massachusetts Medical Society. RETERM delivery is the chief problem in obstetrics today, accounting for 70 percent of perinatal mortality and nearly half of long-term neurologic morbidity. 1,2 Approximately 10 percent of all births are preterm, but most of the serious illness and death is concentrated in the 1 to 2 percent of infants who are born at less than 32 weeks of gestation and who weigh less than 1500 g. Approximately 20 percent of preterm births are the result of a physician’s decision to bring about delivery for maternal or fetal indications, and the remainder follow the spontaneous onset of labor or rupture of the membranes. 3 The rate of preterm delivery has not decreased in the past several decades, 4 but the survival rate of infants delivered prematurely has increased, so that 80 percent of infants weighing 500 to 1000 g now survive. The percentage of survivors with handicaps, however, has changed little, so that the absolute number of surviving preterm infants with handicaps has increased. 2,5 Bacterial infections within the uterus can occur between the maternal tissues and the fetal membranes (i.e., within the choriodecidual space), within the fetal membranes (the amnion and chorion), within the placenta, within the amniotic fluid, or within the umbilical cord or the fetus (Fig. 1). Infection of the fetal membranes, as documented by histologic findings or culture, is called chorioamnionitis; infection of the umbilical cord is called funisitis; and infection of the amniotic fluid is called amnionitis. Although the placental villi may be preferentially involved in blood-borne intrauterine infections such as malaria, bacterial infection within the placenta (villitis) is rare. That preterm delivery may occur in association with leukocytosis of the amniotic fluid or chorioamnion has long been recognized. 6,7 However, the first substantial microbiologic evidence relating intrauterine infection before membrane rupture to preterm delivery was presented only in the late 1970s, when P bacteria were cultured from the amniotic fluid of 7 of 10 women in preterm labor who had intact membranes. 8 This review explores the evidence developed over the past two decades linking intrauterine infection and preterm delivery.