Asthma and smoking during pregnancy cause significant morbidity in both the mother and the offspring. Asthma represents the most common respiratory disorder during pregnancy and smoking rates during pregnancy range from 15-30% in the United States. Maternal asthma and smoking during pregnancy have been shown to increase the rate of intrauterine growth retardation and preterm delivery, as well as increase the risk of wheeze, asthma, respiratory infections, and otitis media in children. However, controlled asthmatics during pregnancy have similar pregnancy outcomes to non-asthmatic pregnancies. Measurement of the fractional concentration of exhaled nitric oxide (FENO) is a new, easily performed, non-invasive method that has been used to assess airway inflammation in adults and children. The long term goal of this study is to establish baseline FENO values and to monitor airway disease in pregnant asthmatics, pregnant smokers and pregnant controls, and to correlate these levels with other inflammatory markers in the mothers and their offspring. These values will be correlated with current methods to diagnose and monitor disease control in these patients. The use of FENO levels in the pregnant asthmatic may prove to be a better method for monitoring disease control and titrating steroid doses in this population. Finally, this study may identify children at higher risk of developing asthma or allergic disease. This could serve to identify factors that may be modified to prevent or limit the development of these diseases in this population.