The American Community Survey (ACS) included an item asking women if they had a birth in the past 12 months (recent birth) because it was assumed that the tabulation of children under age 1 in the household would not be a sufficient way to measure recent or annual fertility.  Newborn children who are not the biological children of the householder may be missed from analyses of characteristics of mothers living with newborns.  This paper has two main points: (1) the evaluation of the use “coresident infants” as a proxy measure for fertility rates compared with the directly asked fertility question, and (2) are there differences among mothers in the likelihood of living with their newborn children. Little is known about the differences between coresident and non-coresident women with a birth in the past 12 months. Using the 2006 American Community Survey, I examine differences between these two groups by a number of demographic and socioeconomic characteristics. These characteristics include: age, citizenship status, disability status, educational attainment, labor force status, marital status, poverty status, public assistance, race and Hispanic origin, region, relationship to householder, residence status, school enrollment, and urban/rural residence.