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Research finds an overarching trend of delayed first births throughout Europe and the United States over the past 40 years (Billari et al. 2007). Many demographers and public health researchers are concerned that delayed childbearing may have negative effects on children's health. My research will investigate two causal mechanisms in which advanced maternal age may affect birth weight. (1) Advanced maternal age will be associated with a decreased ability to give birth to healthy infants, leading older mothers to have decreased birth weights. (2) Older mothers will likely have accumulated more economic and social resources that improve their ability to give birth to healthy infants, leading to increased birth weights. I will be using the North Carolina Birth Certificates (1990-2009) to conduct the analysis. This dataset has 2,252,165 cases that represent the true population of North Carolina's births between 1990 and 2009. The multivariate linear regression analysis finds an inverted U shaped relationship between maternal age and birth weight. For mothers under age 31, maternal age is positively associated with birth weight; for mothers over age 31, maternal age is negatively associated with birth weight. The U shaped relationship between demonstrates an interplay between the social and biological factors of maternal age. The accelerated decline in women's biological ability to give birth to healthy infants begins to outweigh the social benefits of maternal age in their early 30s. This biological decline accelerates as women enter their mid and late 30s and early 40s. [ABSTRACT FROM AUTHOR]