Abstract

Objective: To investigate whether pregnancy induces increased insulin production as a marker of improved beta cell function in women with long-term type 1 diabetes.

Research, Design and Methods: Prospective study of 90 consecutive pregnant women with type 1 diabetes. At 8, 14, 21, 27 and 33 weeks blood samples were drawn for measurements of HbA1c, C-peptide and serum glucose. C-peptide (detection limit: 6 pmol/l) was considered stimulated at a corresponding serum glucose concentration ≥5.0 mmol/l. GAD antibody concentration was determined at 8 and 33 weeks in 35 women.

Results: C-peptide concentrations gradually increased throughout pregnancy regardless of serum glucose concentrations in the 90 women with a median duration of diabetes of 17 years (range 1-36). Among 35 women with paired recordings of stimulated C-peptide, C-peptide production was detectable in 15 (43%) at 8 weeks and in 34 (97%) at 33 weeks (p<0.0001) and median C-peptide gradually increased from 6 to 11 pmol/l (p=0.0004) with a median change of 50% (range −50% to 3271%) during pregnancy. GAD antibodies were present in 77% with no change from 8 to 33 weeks (p=0.85). Multivariate regression analysis revealed a positive association between absolute increase in C-peptide concentrations during pregnancy and decreased HbA1c from 8 to 33 weeks (p=0.003).

Conclusions: Pregnancy-induced increase in C-peptide concentrations in women with long-term type 1 diabetes was demonstrated, even in women with undetectable C-peptide concentrations in early pregnancy. This is suggestive of improved beta cell function and was associated with improvement of glycemic control during pregnancy.