Maintained Pregnancy in the Rat as Associated with Progesterone Administration and Multiple-Nutrient Deficiency

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Abstract
The feeding of a diet containing 0.38% of minerals but otherwise adequate from the day of mating, until autopsy 20 days later, resulted in normal litter size with an average fetus weight 76% of normal. When a diet, containing 94% of sucrose and 8% of hydrogenated vegetable fat was similarly fed, the number of living young at autopsy was 47% of normal, with fetus weights averaging approximately 60% of normal. The daily injection of 5 mg of progesterone was accompanied by an increased litter size, from 1.1 to 7.1 young per mating, when females were fed, for 20 days following mating, a diet consisting solely of sucrose and distilled water. Under these conditions the average fetus weight was reduced to 56% of normal. The results of these studies suggest that progesterone is related either directly or indirectly to the mobilization of nutrients from maternal stores or to the maintenance of placental function, thus permitting the life of the fetus to be maintained for a period of 20 days.