Pregnant albino rats (Sprague-Dawley) and New Zealand Red rabbits were exposed to periodic audiogenic stress throughout pregnancy. Females of both species were sacrificed during each day of the last third of their respective pregnancies. Fetuses were removed, placed in formaldehyde for 1 month, and weighed. Maternal stress during pregnancy produced a marked increase in the number and magnitude of fetuses in both species that exhibited either subnormal or supranormal growth patterns (weights) when compared to control fetuses of the same developmental age. It is postulated that the results in both species are due to an interplay of the disruption of the normal uterine and fetal blood flows, and an imbalance of the maternal endocrine and autonomic nervous system.