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Mild Glucose Abnormalities in Pregnancy Linked to Postpartum Diabetes Risk

Any degree of abnormal glucose homeostasis during pregnancy is predictive of glucose intolerance 3 months after delivery, according to a new report. The results, according to the authors, suggest that antepartum screening for gestational diabetes is useful in gauging a woman’s future risk of pre-diabetes and type 2 diabetes.

"It is well-recognized that women with gestational diabetes are at increased risk of developing type 2 diabetes in the future," lead author Dr. Ravi Retnakaran, from Mount Sinai Hospital in Toronto, told Reuters Health. "The novel finding of our study is that even women with mildly abnormal glucose levels in pregnancy have an increased risk of developing pre-diabetes or diabetes after their pregnancy."

Dr. Retnakaran added, "We weren’t surprised by this finding, as we had hypothesized that any degree of glucose intolerance in pregnancy should predict an increased future risk of pre-diabetes or diabetes, although we were surprised by the magnitude of this increased risk."

The study involved 487 women who underwent antepartum diabetes screening with a glucose challenge test (GCT) and a diagnostic oral glucose tolerance test (OGTT). In addition, the OGTT was repeated at 3 months postpartum to assess glucose homeostasis.

On the basis of the two antepartum tests, the women were divided into four groups: 1) gestational diabetes mellitus, 2) gestational impaired glucose tolerance, 3) abnormal GCT with normal OGTT, and 4) normal GCT and normal OGTT.

The prevalence of postpartum glucose intolerance (diabetes or pre-diabetes) rose as the severity of abnormal glucose homeostasis during pregnancy increased, Dr. Retnakaran and colleagues found. The prevalence ranged from just 3.2% for patients with normal GCT and normal OGTT to 32.8% for those with gestational diabetes (p < 0.0001).

Compared with normal glucose findings during pregnancy, abnormal GCT/normal OGTT, gestational impaired glucose tolerance, and gestational diabetes increased the risk of postpartum glucose intolerance by 3.6-, 5.7-, and 14.3-fold, respectively.

The results also show that insulin sensitivity and pancreatic beta-cell function, both during pregnancy and at 3 months postpartum, fell as glucose homeostasis during pregnancy went from normal to gestational diabetes (p < 0.0001).

"The significance of our study rests in its illustration of the concept that the spectrum of abnormal glucose homeostasis in pregnancy identifies a continuum of risk for postpartum glucose intolerance and that this spectrum extends to levels of antepartum dysglycemia far less severe than gestational diabetes mellitus," the research team concludes.

Practice Pearls:

  • Any degree of abnormal glucose homeostasis in pregnancy independently predicted an increased risk for glucose intolerance postpartum. The prevalence of postpartum glucose intolerance (prediabetes or diabetes) increased across the 4 baseline glucose tolerance groups.
  • Both in pregnancy and at 3 months postpartum, ISOGTT and pancreatic beta-cell function progressively decreased across the groups. Antepartum GDM screening therefore offers an opportunity to obtain insight into a woman’s future risk for prediabetes and type 2 diabetes.

Diabetes Care. Oct. 2008;31:2026-2031.