Hepatic insulin extraction in human pregnancy. 
The hepatic degradation of insulin in late pregnancy has been estimated by determination of the molar C-peptide: Insulin (C/l) ratio under fasting conditions in 20 normal women in late pregnancy and again 4--8 weeks post-partum.  Fasting plasma C-peptide and insulin concentrations were both significantly enhanced in pregnancy.  However, since the relative gestational increments in plasma C-peptide and insulin concentrations were of almost the same magnitude, the C/l ratio remained unaffected by pregnancy (7.3 +/- 0.07 (mean +/- S.E.M) (pregnancy) vs. 7.4 +/- 0.8 (post-partum), N.S.).  The results suggest that, in pregnancy, peripheral hyperinsulinaemia is due, in general, to pancreatic hypersecretion rather than to diminished hepatic extraction of insulin.