These included weight changes, behavior during irradiation, perceptual-motor development of infants, maternal care, urinary catecholamines, plasma cortisol, PHA-stimulated response of peripheral blood lymphocytes, and different aspects of electroencephalographic activity. None of these measures differed in any systematic way among either dams or offspring of the various treatment groups. In contrast to these results, a greater number of offspring died in the group exposed both pre- and postnatally to 10 mW/cm2 than in any of the other groups. Table 1 shows the number of live births and deaths for each of the treatment groups as well as other pertinent information of the study. The gestation period for the squirrel monkey is approximately 22 weeks; therefore, exposures began primarily in the second trimester for all groups. As can be seen from the table, the percentage of live births was comparable among the different groups, but the percentage of infant deaths was not. No infants died in the control group, compared with 22, 17, and 56% in the 0.1, 1.0, and 10.0 mW/cm2 groups, respectively. The annual mortality rate during the first year of life of animals born in our colony over the last 5 years has averaged 20 to 25%, so the results obtained on the 0.1 and 1.0 groups would not appear to be atypical. However, the number of deaths in the 10.0 group was substantially larger than the normal mortality rate and therefore would appear to be a direct result of the treatment. Moreover, four of the five infants that died in the 10.0 group were exposed both pre- and postnatally, suggesting a cumulative effect of the microwave exposures. In all but one case, the deaths of infants were completely unexpected and occurred without prior warning. In each case, the dead infant was found in its home cage in the morning. The only infant that did not die suddenly was one in the 10 mW/cm2 group exposed pre- and postnatally; it died when it was 177 days old, after having become gradually weaker over a 9-day period. Gross necropsies were performed on only four of the nine infants that died, and in no case was the cause of death obvious. Because of the small number of subjects in the different treatment groups the significance of these mortality figures were questionable at the end of the study. Thus, in order to provide a more definitive answer as to the relative safety of pre- and postnatal exposure to 10 mW/cm2 equivalent, a subsequent experiment was undertaken with a larger population of animals in which offspring viability at 10 mW/cm2 was compared with that of sham exposure at 0 level. In this latter study pregnant monkeys were irradiated for 3 hours daily, 7 days/week beginning in the first trimester of pregnancy in the same chambers used in the first study. After parturition, dams were irradiated with their offspring for 6 months; then the offspring were irradiated alone until 9 months of age. Although this study has not yet been completed, the results obtained so far have not verified the original mortality findings. Moreover, as found before, both the general health and growth of exposed offspring did not differ from controls.
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