Prenatal maternal distress is associated with an at-risk developmental profile, yet there is little fetal evidence of this putative in utero process. Moreover, the biological transmission for these maternal effects remains uncertain. In a study of n=125 pregnant adolescents (ages 14-19), ambulatory assessments of daily negative mood (anger, frustration, irritation, stress), physical activity, blood pressure, heart rate (every 30min over 24hr), and salivary cortisol (six samples) were collected at 13-16, 24-27, 34-37 gestational weeks. Corticotropin-releasing hormone, C-reactive protein, and interleukin 6 from blood draws and 20min assessments of fetal heart rate (FHR) and movement were acquired at the latter two sessions. On average, fetuses showed development in the expected direction (decrease in FHR, increase in SD of FHR and in the correlation of movement and FHR (coupling)). Maternal distress characteristics were associated with variations in the level and trajectory of fetal measures, and results often differed by sex. For males, greater maternal 1st and 2nd session negative mood and 2nd session physical activity were associated with lower overall FHR (p<.01), while 1st session cortisol was associated with a smaller increase in coupling (p<.01), and overall higher levels (p=.05)findings suggesting accelerated development. For females, negative mood, cortisol, and diastolic blood pressure were associated with indications of relatively less advanced and accelerated outcomes. There were no associations between negative mood and biological variables. These data indicate that maternal psychobiological status influences fetal development, with females possibly more variously responsive to different exposures. (c) 2015 Wiley Periodicals, Inc. Dev Psychobiol 57: 607-625, 2015.