Pregnant H-2 congenic mice, C57BL/10, B10.A, B10.A(15R), and B10.A(18R) were fed Purina Laboratory Chow 5001 or the same diet supplemented with 400 IU vitamin A dissolved in corn oil or 0.4% (w/w) myo-inositol. On the 18th day of gestation, the dams were sacrificed, and the fetuses were weighted, sexed, and examined for developmental abnormalities. Term fetal weight was found to be significantly reduced in progeny of dams bearing d alleles distal to Ea in the H-2 complex when the diet was supplemented with vitamin A or myo-inositol (B10.A and B10.A [18R]). Fetuses from dams of all strains fed the diet supplemented with vitamin A had significantly increased frequencies of microphthalmia; the frequency of microphthalmia was moderately but not significantly increased in one of the two strains fed the diet supplemented with myo-inositol (B10.A[15R] but not B10.A[18R]).