B-cell Function in Newborn Infants of Diabetic Mothers

Serum concentrations of glucose, C-peptide, IRI (Immunoreactive insulin) and proinsulin were determined in 31 insulin-dependent diabetic mothers and their newborn infants and in 13 nondiabetic mothers and their babies at the time of delivery. Eleven mothers with long-term diabetes had insulin antibodies and low or undetectable C-peptide levels (mean ± SEM: 0.04±0.01 nmol/l). Diabetic mothers without insulin antibodies had a mean C peptide value of 1.18 nmol/1 (range 0.05–3.00) and the non-diabetics 0.95 nmol/l (0.28–2.4). Blood glucose values (2 to 4 hours after birth) of less than 1.7 mmol/l were observed in 7 of the 11 babies with antibodies and in 3 of the 20 babies without antibodies. C-peptide in the 31 babies of diabetic mothers correlated to maternal glucose (p < 0.05). In addition the mean glucose value (2–4 hours) was negatively correlated to IRI and proinsulin (p < 0.01) in the babies without antibodies, confirming that elevated maternal glucose leads to increased insulin secretion at the time of birth, which may lead to hypoglycaemia. In babies without antibodies birth weight correlated to their C-peptide (p < 0.01) and proinsulin (p < 0.01). The 31 babies of the diabetic mothers were born with higher C-peptide (1.01±0.16 nmol/ 1) than babies of non-diabetic mothers (0.39±0.04 nmol/1). The newborn infants secrete significantly more proinsulin than their mothers. Babies of mothers with insulin antibodies were born with the same concentrations of antibodies (Pearson correlation coefficient = 0.98) as in their mothers, but total IRI was higher in these babies, due in part to human proinsulin being bound to the antibodies. There were significant correlations between insulin antibodies on the one hand, and IRI, proinsulin and C-peptide on the other, in the 11 babies, p < 0.001, p < 0.001 and p < 0.01, respectively, the last indicating increasing B-cell activity with higher antibody levels.