The main purpose of these experiments was the prevention of congenital malformations in offspring of alloxan-diabetic mice by insulin injections administered during pregnancy. The optimum dose of insulin and timing of its administration are described for mice made hyperglycemic by injection of alloxan of 80 mg. per kilogram of body weight.

Copulated female mice were given alloxan intravenously on the fourth day of gestation, followed by 0.4 units of Lente insulin every twelve hours beginning thirty to thirty-six hours after alloxan injection, and continuing until the sixteenth day of gestation. The control group was given only the alloxan injection on the fourth day of gestation. Pregnant mice were sacrificed on the nineteenth day of gestation; fetuses were removed by laparotomy and examined for external defects and skeletal deformities.

In fifty successful pregnancies treated with insulin, only one fetus (0.2 per cent) of 472 was malformed with a cleft palate; in fifty successful pregnancies given alloxan alone fourteen or 28 per cent of mice had one or more malformed fetuses. Altogether, twenty-two or 5.0 per cent of 437 fetuses in the latter group had malformations which included craniorhachischisis (seven fetuses), cleft palate (six fetuses), club foot (five fetuses), spina bifida, anencephalus, open eye, microphthalmia and skeletal deformities in one or more fetuses. The difference between the alloxan group and insulin treated group in the number of mothers having malformed fetuses, and in the number of malformed fetuses produced was statistically significant according to the chi-square test with a probability level of less than 0.01. In the alloxan group, increased body weight associated with advancing pregnancy was less advanced in mice having malformed fetuses than in those having normal fetuses. The foregoing tendency was also statistically significant with a probability level less than 0.01. However, no appreciable correlation was observed between the magnitude of hyperglycemia of mother mice and the frequency of fetuses with congenital malformations.

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