Washington State Birth Registry data of the years 1980-1982 of 803 women with intrapartum fever, who gave birth to a singleton, and of 1,714 control women without such diagnosis selected at random from the child-bearing population were studied for risk factors and maternal and neonatal outcome variables. Cases were significantly more often less than 21 years old, nonwhite, unmarried, nulligravid, and nulliparous than controls, and had significantly shorter gestational ages and longer birth intervals. The risk of intrapartum fever was higher in nulliparous than in nulligravid women [adjusted odds ratio (OR) 4.0 and 2.3, respectively]. This risk difference led to the discovery of increased fetal and perinatal losses prior to the pregnancy under study: cases lost 160 of 390 (41%) previous pregnancies while controls lost 142 of 1,180 (12%; OR = 5.1; p less than 0.001). In a matched analysis, spontaneous abortions (less than 20 weeks gestation) immediately preceding the pregnancy under study were found to increase the risk of intrapartum fever by 2.7 times.