An increasing body of literature documenting what has become known as "the Epidemiological Paradox" has shown that some immigrant groups to the United States tend to have healthier birth outcomes than would be expected given their sociodemographic profiles. Furthermore, the children of these immigrants do not seem to enjoy the same advantage in reproductive health that their parents did. This phenomenon, though amply documented in the literature, has not been sufficiently explained. We investigate the role of assimilation in this paradox, and we do so within a spatial framework. We examine the effect of residence in a Mexican enclave in the attenuation of risk of low birth weight (LBW) for Mexican-origin mothers in San Diego County, California. We find that Mexican-origin women do seem to enjoy a reduced risk of giving birth to an LBW baby when they live in a Mexican enclave.