Responses of Animal Fetuses and Neonates to Intra-Uterine Stress

THREE general approaches have been followed in this report: (1) Pentobarbital sodium was administered to mothers at dosage levels 50% lethal for the young of the litter. Physiologic measurements were obtained on the mother during the period of drug action. Surviving young were studied as neurological, behavioral, and neuropathological specimens. (2) By means of a water bath technique control fetuses were delivered from one uterine horn while littermates in the other horn were subjected to hypoxic stress by uterine clamping, or the mothers were heavily sedated. These fetuses were delivered later, generally after resuscitation, and were compared with controls. (3) Similarly, intrauterine respiration was studied as a spontaneous event in one horn, and as an induced event in the other. A colloidal suspension of thorium dioxide (Thorotrast), injected in amnio, was sought in fetal or neonatal lungs. Injected intact animals were also checked by x-ray examination at various stages of gestation