Introduction Anthropogenic activities produce complex varieties and quantities of air pollutants that affect public health. Characterization of air pollution depends on population density and settling characteristics, energy consumption, industrial processes, meteorological and geographical factors, urban growth, land-use changes, habits of transportation/cooking, etc. Maternal and Child health are important public health issues. Pregnancy induces physiological adjustment in women; tidal volume increases (requires 40%+ oxygen) and induces changes in respiratory mechanism. Air pollution inhaled and metabolized by the mother is transmitted to developing fetus. Inhalation of larger than normal tidal volume of polluted air enhances risks to mother and fetus. A developing fetus is vulnerable to air pollution commonly found in urban environments. WHO data shows that low birth weight is a major cause of children disease burden and that 95% of children with low weight are born in developing countries like Peru. Several studies suggest that a fetus is prone to genetic damage and cleans air pollution less efficiently than adults. A fetus is sensitive to air pollutants that produce DNA damages. This is the first study of personal exposure of pregnant women to air pollution. Air quality data from Monitoring Stations have been used to linked air pollution exposure of pregnant women to adverse health effects on fetus development. However, this data does not account for local habitat, personal activity or exposure pattern, factors that affect exposure. Personal exposure to CO, VOC's and microenvironment exposure to PM-2.5 were studied in 45 non-smoking pregnant women in Trujillo, Peru, an urban city of 732,566 people located at sea level where 80% of outdoor air pollution is from motor vehicles with emission rates similar to 1974 USA levels and 52% of people live in poverty. At the time of this study (2002) and out of 2330 singleton live births, 32.1% of pregnant women reported anemia, 13% did not have pre-natal care and 11.4% of full term newborns have low birth weight. Method A local team was trained to recruit 45 non-smoking pregnant women residing in Trujillo. Questionnaires were designed to obtain demographic data, environmental characterization of home/employment/school, method and habit of transportation/cooking and, time budget activity and details of type of activity during study period. Air pollutants were measured at breathing zone using passive and active methods. Real time CO data was measured every 30 seconds. Exposure was measured for one day during normal activities from 8–13 hours. GC-MS was used to analyze VOC's data. Active PM-25 data was collected at the most used microenvironment. Results CO TWA: 2.74 PPM/Hr (SD = 2.90), Benzene: 7.82 Ug/M3 (SD = 4.28), Toluene: 516.00 Ug/M3 (SD = 901.9), PM-2.5 = 51.77 Ug/M3 (SD = 24.43) Discussion This study shows that exposure is very dependent on local habitat, personal activity and exposure pattern. CO and PM-2.5 concentrations were higher than those reported in studies that have linked pregnant women exposure to these air pollutants to adverse pregnancy outcomes. High CO exposure, rate of change of frequent CO concentrations and exposure pattern favors bioaccumulation of COHb and longer than normal elimination time for COHb. Real time CO data offers the opportunity to elaborate on pharmacokenetics and possible mechanisms of this exposure. Base on WHO guidelines, 40% of pregnant women, in one day, were exposed to higher toluene exposure for one week. A significant percentage of pregnant women exhibited PM-2.5 exposure concentration in excess of USA EPA daily standard.