Lifetime Risk for Type 2 Diabetes Increased in Women With Gestational Diabetes

Laurie Barclay, MD

May 26, 2009

May 26, 2009 — Women who have gestational diabetes mellitus during pregnancy have a 7.5-fold increased risk for the development of type 2 diabetes after delivery, which persists for their lifetime, according to the results of a systematic review and meta-analysis reported in the May 23 issue of The Lancet.

"Women with gestational diabetes are at increased risk of developing type 2 diabetes, but the risk and time of onset have not been fully quantified," write Leanne Bellamy, MBBS, from Northwick Park Hospital, London, United Kingdom, and colleagues. "We therefore did a comprehensive systematic review and meta-analysis to assess the strength of association between these conditions and the effect of factors that might modify the risk."

A search of EMBASE and MEDLINE identified cohort studies in which women who went on to have type 2 diabetes after gestational diabetes were reevaluated between January 1, 1960, and January 31, 2009. A hand search of 205 pertinent reports led to selection of 20 studies, which enrolled a total of 675,455 women who had a total of 10,859 type 2 diabetic events.

A random-effects model allowed determination of calculated and pooled unadjusted relative risks (RRs) for each study. Separate analyses were performed for subgroups of studies based on the number of cases of type 2 diabetes, ethnicity, duration of follow-up, maternal age, body mass index, and diagnostic criteria.

Compared with women who remained normoglycemic during pregnancy, those with gestational diabetes had a higher risk for the development of type 2 diabetes (RR, 7.43; 95% confidence interval [CI], 4.79 - 11.51). RRs were fairly consistent among the different subgroups evaluated, although the largest study (659,164 women; 9502 cases of type 2 diabetes) had the largest RR (12.6; 95% CI, 12.15 - 13.19).

"Increased awareness of the magnitude and timing of the risk of type 2 diabetes after gestational diabetes among patients and clinicians could provide an opportunity to test and use dietary, lifestyle, and pharmacological interventions that might prevent or delay the onset of type 2 diabetes in affected women," the study authors write.

Limitations of this study include heterogeneity in the overall effect estimate, inability to stratify results according to family history of diabetes and previous gestational diabetic pregnancy, and possible publication bias.

In an accompanying comment, Rhonda Bentley-Lewis, from Brigham and Women's Hospital in Boston, Massachusetts, notes that clinicians must be educated regarding the link between gestational diabetes and subsequent type 2 diabetes.

"The present task is to ensure that this information is disseminated to clinicians and that the information is used to target prevention efforts to those who have had gestational diabetes," Dr. Bentley-Lewis writes. "Furthermore, we need to address how progression from gestational diabetes to type 2 diabetes can be halted so that evidence-based approaches to management can be developed. In view of the compelling data that link gestational diabetes to the development of type 2 diabetes, we as clinicians are afforded the rare opportunity to alter the natural course of disease and change the future health of women today."

This study has received no funding. One of the study authors is a member of the editorial board of Drug and Therapeutics Bulletin; has been an advisor to GlaxoSmithKline and London Genetics; and has received honoraria for speaking at educational meetings sponsored by the pharmaceutical industry, all or most of which he has donated to charity. The other study authors and Dr. Bentley-Lewis have disclosed no relevant financial relationships.

Lancet. 2009;1738-1740, 1773-1779.

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