Gestational Diabetes Is a Herald of NIDDM in Navajo Women: High rate of abnormal glucose tolerance after GDM

  1. Fred A Connell, MD
  1. Northern Navajo Medical Center, University of Washington Seattle, Washington
  2. Public Health Service Indian Hospital Shiprock, New Mexico School of Public Health and Community Medicine, University of Washington Seattle, Washington
  1. Address correspondence and reprint requests to Jonathan R. Steinhart, MD, Northern Navajo Medical Center, Box 160, Shiprock, NM 87420. E-mail: jsteinh532{at}aol.com

Abstract

OBJECTIVE To estimate the rate of deterioration of glucose tolerance and evaluate risk factors for development of NIDDM in Navajo women with a history of gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS A retrospective analysis of 111 GDM deliveries over a 4-year period, 1983–1987, was conducted in 1994 to determine glucose tolerance status. Patients who had not developed NIDDM were recalled for a 2-h glucose tolerance test (GTT). Tested and non-tested patients were compared, as estimate of conversion to NIDDM was calculated, and risk factors for NIDDM were evaluated. A life-table analysis was developed to estimate the probability of NIDDM after GDM.

RESULTS At the time of chart review, 32 patients (29%) had already been diagnosed with NIDDM. Of the patients, 79 were offered GTT testing, and 56 (71%) returned for follow-up; 15 were diagnosed with NIDDM and 17 with impaired glucose tolerance (IGT); 47 (42%) and 64 (58%) patients in the cohort had developed NIDDM or NIDDM/IGT at the conclusion of the study period. Patients who developed NIDDM had greater BMIs, parity, and infant weights. Fasting blood glucose > 5.83 mmol/l, GTT > 41.63 mmol/l, and recurrence of GDM were associated with later NIDDM. A life-table analysis estimated a 53% likelihood of having NIDDM at an 11-year follow-up; a second model, based only on patients with known NIDDM status, predicted a 70% rate of NIDDM at an 11-year follow-up.

CONCLUSIONS A high proportion of Navajo women with GDM progressed to NIDDM. Postpartum counseling and periodic GTTs are recommended.

  • Received September 24, 1996.
  • Accepted January 9, 1997.
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