Compared to infants of other races, African American (AA) infants are more likely to have mothers with high rates of stress, to be born preterm, and to reside in poverty, whereas they are less likely to be breastfed. These disparities translate into higher risks for neurocognitive and social-emotional developmental delays. The microbiota-gut-brain axis - which functions through neural, hormonal, and immunologic pathways - is receiving growing attention as an important contributor to neurodevelopment. The gut microbiome is established at birth from maternal flora and varies according to perinatal factors such as mode of delivery, gestational age and size, type of feeding, and antibiotic exposure. Thereafter, diet, illness, vaccination, and antibiotic exposures further influence microbiome development. Thus, prenatal and postnatal biobehavioral exposures that affect the microbiome-gut-brain axis in the critical first years of life may significantly impact the developing brain. The proposed research will investigate whether the composition of the gut microbiome associates with exposure to prenatal and postnatal maternal stress and contributes to adverse neurocognitive and social emotional outcomes for AA infants over the first 18-months of life. To accomplish this, we will leverage biobehavioral data from our on-going longitudinal study of preterm birth in AA women (R01 NR014800), that is enrolling a socioeconomically diverse cohort of ? 800 pregnant AA women and following them at 8-14 and 24-30 weeks' gestation through delivery. The parent study provides data on prenatal maternal stress, psychoneuroimmune (PNI) dysfunction (e.g., pro- and anti-inflammatory cytokines, cortisol) and pregnancy and birth outcomes (e.g., infections, antibiotics, delivery mode, gestational age). For the birthed AA infants, from 1-week through 18-months of age, the proposed study will evaluate: (1) Environmental and genetic influences on the gut microbiome; (2) The pathways between infant gut microbiome, PNI function, and neurocognitive and social-emotional development; and (3) The associations among the infant gut microbiome, maternal caregiving and stress, and infant neurocognitive and social-emotional development Because many factors that influence the microbiome are modifiable, the knowledge gained by achieving our Aims holds tremendous potential for promoting the health of the next generation of AA families. The success of this research is supported by our multidisciplinary collaboration of scientists representing expertise in the microbiome, obstetrics and maternal-child health, genetics, nutrition, stress, epidemiology and informatics; the overlap of key personnel for the proposed and parent studies; and support from Emory Clinical and Translational Science Institute (CTSA award # NIH UL1TR000454) and Genomics Core Laboratory. Also, Atlanta is home to AA women of broad socioeconomic status, providing a diverse sample of AA families, which allows for sufficient variation in the biobehavioral factors under study to distinguish their independent and interactive effects on the microbiome and infant neurocognitive and socio-emotional development.