Insulin immunogenicity in pregnancy: maternal and fetal studies.

Antibodies to insulin were found in 92% of the 138 insulin-treated pregnant diabetic patients studied. No effect of pregnancy was shown on insulin antibody levels. Higher insulin antibody levels were significantly associated with the previous use of conventional insulins. Change from conventional to highly purified porcine insulin during pregnancy produced a significant reduction in insulin antibody levels. The combination of protamine zinc and soluble insulin used before pregnancy was found to be the most immunogenic. Insulin antibodies were freely transferred to the fetus but not detectable after the first 8 months of life. No insulin antibodies were found in the cord blood or during the next few weeks in the infants of mothers who had no antibodies to their injected insulin. There was a tendency for higher insulin antibody levels to be associated with indices of neonatal morbidity but not with percentile birth weights and C-peptide levels in cord sera.