When babies are premature, or born before they are fully developed, they face many different medical problems, some of which are quite devastating, such as cerebral palsy, mental retardation, blindness, deafness, severe intestinal problems, and developmental delays. Unfortunately, in more than half the cases of premature births, there is no procedure or test that an obstetrician can employ to predict if a fetus is at risk for premature birth, especially when the mother is healthy. This study seeks to determine if certain factors found in the urine undergo specific changes that can be used to detect premature births of this type before they happen.