Maternal social stress disrupts reproduction of hamsters drinking high-calorie fluids.

Adding maternal social stress, induced by housing in pairs, to maternal consumption of high-calorie fluids adversely affected hamster reproduction. Pregnancy outcomes of 67 dams housed either alone or in pairs, and given either water (WAT), or isocaloric solutions of either 30% ethanol (ETH), sucrose (SUC) or propylene glycol (PG), were compared. Pups of unpaired dams drinking any high-calorie fluid weighed less than those drinking water, but no other deficits were found. Among paired dams, those designated submissive on the basis of agonistic behavior and drinking either SUC, ETH, or PG, had fewer viable pups and more fetal resorptions and stillborn pups than WAT dams. Also, dominant PG dams delivered few pups and both dominant and submissive PG dams delivered malformed pups or embryos. Whether paired or unpaired, litters of SUC and ETH dams were similar. Drinking any high-calorie fluid reduced maternal food and fluid intake and weight gains below that of water, but pairing had no additional effect on dams.

Litter deficits of socially stressed and low status hamster dams.

The effects of maternal social stress, induced by pairing pregnant females, and social status, measured by agonistic behavior within pairs, on pup development was investigated in hamsters. Using litters from untreated first pregnancies as a control, 40 dams were housed either alone or paired with another dam during their second pregnancy. Within a pair, the dam with more aggressive and fewer defensive responses than the other was considered dominant. Compared to their first unpaired litters, second litters of paired dams were smaller in number. Comparisons among second litters showed that paired dams, especially submissive dams, had fewer pups than unpaired dams. It was concluded that both maternal social stress and low status increase intrauterine mortality.