Previous epidemiological research on the effects of moderate pollution levels on prenatal health suggest negative effects but have produced inconsistent results.
Chart 1 provides a list of previous studies examining this relationship, limiting our review to developing countries that are likely to have comparable levels of pollutions to New Jersey For example, Ritz and Yu (1999) report that CO exposure in the last trimester of pregnancy increased the incidence of low birth weight (defined as birth weight less than 2500 g), while Ritz et al. (2000) report that CO exposure in the 6 weeks before birth is correlated with gestation in some regions of southern California but not in others.
Ritz et al. (2000) report that PM10 exposure 6 weeks before birth increases preterm birth, while Maisonet et al.(2001) find that PM10 has no effect on low birth weight.