The health of a mother directly affects the fetus during pregnancy. High levels of vehicle pollution where pregnant women reside can have adverse health effects on fetuses.

The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. (August 2019)

In the United States about 10% of the population, 33 million people, live within 900 meters of a high traffic road^[1] High-traffic roads are commonly identified as being host to more than 50,000 vehicles per day, which is a source of toxic vehicle pollutants.^[2] Previous studies have found correlations between exposure to vehicle pollutants and certain diseases such as asthma, lung and heart disease, and cancer among others. Car pollutants include carbon monoxide, nitrogen oxides, particulate matter (fine dusts and soot), and toxic air pollutants ^[3] While these pollutants affect the general health of populations, they are known to also have specific adverse effects on expectant mothers, their fetuses and children. The purpose of this article is to outline how vehicular pollutants affect the health of expectant mothers and the adverse health effects these exposure have on the adult.

Areas with high levels of nitrogen dioxide in the air, which is an output of vehicular air-pollution, are shown to have negative effects on fetuses. Effects of the exposure include reduced fetal growth, premature birth, and respiratory conditions. Two studies were conducted to evaluate the effects of nitrogen dioxide on fetuses in the southern United States as well as Valencia Spain. In the United States, babies that were born prematurely were 94% more likely to have been exposed to high levels of pollution than those that were not premature. In Spain, fetuses that were small for gestational age in terms of weight were 37% more likely to have been exposed to high levels of air pollution than those that were not small for gestational age in terms of weight.^[4][5]

In Los Angeles County, researchers found a higher risk in premature birth (10-20%) and low birth weight for infants whose mothers lived near high traffic areas ^[6] Studies conducted on populations living near the 405 and 710 interstates in Southern California found their exposure to particulate vehicle emissions to be almost 25 times higher than for people living 1000 ft from the freeways. This research also concluded that particulate vehicle emissions are more toxic to children's health than other particles such as Carbon Monoxide and Nitrogen Dioxide ^[7][8]

A previous study conducted in the Los Angeles Basin of Southern California reported a consistent association between levels of CO and particulate matter during the first trimester and the last six weeks prior to birth and risk of preterm birth. Prematurity in babies is accompanied by an array of health complications. Children born prematurely are at highest risk for developing Infant respiratory distress syndrome, gastrointestinal, and hematologic diseases, central nervous system (CNS) problems such as hearing loss, are more prone to infections, and at risk for hearing and vision loss.

Babies born of low weight are also at risk for respiratory, gastrointestinal, cardiac, CNS, infection and vision problems. These gestational issues persist until the adult years for most children and result in high blood pressure, Type II Diabetes, and other heart diseases.

Prematurity and Low Birth Weight caused by air pollution also affects fetal brain development. This is of importance since lack of proper brain development will not allow a child's brain to form proper synapse connections which will negatively affect the child's speech, learning abilities, and social skills.

Exposure to air pollution not only affects newborns in early stages of their development, it can also have lifelong consequences for children exposed from the time of conception to when they reach two years of age. Air pollution has been found to cause lower birth weights, insufficient development of the immune system and organs, and premature births. These birth effects have been linked to respiratory issues that can persist into one's long-term health.^[14]

Exposure to vehicle air pollutants has been noted as primary cause for infant mortality and morbidity, and is also argued to be a cause of chronic diseases such as asthma in child and adulthood ^[15]

Autism is a spectrum of disorders that range from a severe inability to communicate and some mental disabilities to milder symptoms such as attention disorders. Some claims exist that the incidence of autism is higher for babies whose mothers spend time in ‘high traffic pollution’ areas compared to mothers who spend their pregnancy in cleaner air. In a recent study conducted by UCLA, air pollutant levels were measured for mothers who had children with autism and then compared to air pollutant levels in environments for mothers who had children without autism. This study found that babies who were exposed to higher levels of pollutants while in the womb had a 10% higher risk of autism than babies who had low levels of exposure; another finding from this study is that fine particulates had the strongest association with autism ^[23]

Motor vehicle emissions are not solely a United States issue. Of the 10 cities with the most traffic, there are no cities from the United States listed.^[24] The United States also has regulations regarding what and how many emissions vehicles are allowed to emit that are on the road. This is done by the USEPA and they are currently working on new regulations.^[25] Of the countries that have vehicle emission standards, the European Union and Japan have the most strict regulations. These standards have been added because it is shown that regulating fuel economy is effective in controlling oil demands for the country as well as reducing their greenhouse emissions.^[26]

Respiratory and allergic disorders among children in Japan were studied after the implementation of new regulations were put in place and it showed the prevalence of asthma and other respiratory disorders decreased.^[27] There have also been more recent studies showing that the incidence of asthma cases worldwide is increasing in children. Much of this increase is due to the increase in NO2 which is a gas that is emitted from motor vehicles among other sources.^[28]

Across the United States, vehicle emissions make up a large portion of air pollution, especially in urban areas. An epidemiological study conducted by the National Institute of Health compared pregnancy loss to local vehicle emissions, specifically nitrogen dioxide (NO₂). The study used data from Boston, Massachusetts and Tel Aviv, Israel, and both regions observed associations between pregnancy loss and NO₂, largely in the second trimester of pregnancies. This study further increases scientific confidence that vehicle emissions can be detrimental to pregnant individuals and fetuses and that these findings are consistent in different geographic locations and among different populations.^[29]

• Environmental impact of transport
• List of most-polluted cities by particulate matter concentration