Although the mechanisms responsible for the onset of preterm labor in human pregnancy are unclear, animal studies have demonstrated that decreased nutrient intake is associated with increased uterine prostaglandin F metabolite production and spontaneous uterine contractions. The purpose of this study was to assess the association of maternal nutrition and dehydration with preterm uterine contractility. Pregravid weight-for-height, pregnancy weight gain at 30 weeks' gestation, urine specific gravity, ketonuria, and dependent and generalized edema were measured in 30 women who had preterm uterine contractions and in 30 women matched for race, gestational age, socioeconomic status, and smoking who reported no symptoms of preterm contractility. Data were analyzed with the paired-difference t test, Fisher's exact test, and the Cochran-Mantel-Haenszel test. No statistical association was found for dehydration (high urine specific gravity) and preterm contractility. However, pregravid weight below standard body weight-for-height was statistically associated with preterm contractions (P less than .001), as was low weight gain at 30 weeks' gestation (P = .04). There was an association between preterm contractions and both ketonuria (P less than .0001) and the absence of edema (P = .02). Inexpensive clinical measurements of nutritional status may help to identify women at risk for preterm uterine contractility.