OBJECTIVE To ascertain whether childbearing would decrease oral glucosestimulated insulin and C-peptide levels and increase the risk of NIDDM and impaired glucose tolerance in a population of Hispanic and non-Hispanic white women residing in the San Luis Valley of Colorado. Several investigators have related childbearing to subsequent abnormal glucose tolerance.

RESEARCH DESIGN AND METHODS In a population-based case-control epidemiological study, diabetic patients 20–74 yr of age (n = 196) and randomly sampled control women subjects (n = 735) underwent a glucose tolerance test, a physical examination, and an in-person standardized interview. The relations between the live-birth number and fasting and oral glucose stimulated glucose, insulin and C-peptide concentrations, and NIDDM and impaired glucose tolerance were estimated using linear or logistic regression to adjust for extraneous variables.

RESULTS In women selected as control subjects, the live-birth number was related to a significant decrease in the sum of 1- and 2-h C-peptide concentrations (coefficient = −0.077, P <0.001) and the logarithm of the sum of 1- and 2-h insulin concentrations (coefficient = −0.014, P = 0.02). After adjustment for subscapular skin-fold thickness, the relative odds of NIDDM for the live-birth number, which was small and of borderline significance, diminished (odds ratio = 1.04 for one birth, P = 0.18). Findings were similar for impaired glucose tolerance.

CONCLUSIONS Childbearing was related to lower C-peptide and insulin levels in Hispanic and non-Hispanic women of the San Luis Valley. It had little apparent effect on later risk of NIDDM or impaired glucose tolerance.