How Type 2 Diabetes Complicates Pregnancy

The other part of the problem could well be that we are not treating these patients intensively enough.

Early Detection, Intensive Treatment

We must intensify efforts to educate patients and physicians about the risks of type 2 diabetes in pregnancy and the need to control glucose levels before pregnancy occurs.

The benefits of preconception care in reducing congenital malformations in the context of diabetes are clear. In a meta-analysis of studies on preconception care in women with diabetes published from 1970 to 2000, the pooled rate for major malformations among a total of approximately 2,600 offspring was 2.1% in the group that received preconception care compared with 6.5% in the group that did not receive the care.

Another look at major and minor anomalies together showed a pooled rate of 2.4% in the preconception care groups compared with 7.7% in the women who did not receive this care. Early first trimester mean glycosylated hemoglobin values also were significantly lower in the women who received preconception care (QJM 2001:94;435–44).

Stepping up our promotion of preconception care is a first step toward primary prevention of diabetes-associated complications, but we also ought to set new criteria in our practices that stipulate that patients who are obese or have a previous history of gestational diabetes will have fasting plasma glucose tests performed in conjunction with the first prenatal office visit or immediately afterward.

A deliberate methodology for identifying patients early on who are at risk for type 2 diabetes and testing them promptly—and not waiting for standard gestational diabetes testing—will enable us to impact pregnancy outcomes.

Neither the American Diabetes Association nor other medical groups have yet issued guidelines on fasting plasma glucose testing in early pregnancy, but this does not mean we shouldn't pursue such testing. Currently, for adults younger than 45 years, the ADA recommends testing to detect prediabetes and type 2 diabetes in individuals who are overweight or obese and who have one more risk factor. Giving birth to a baby weighing more than 9 pounds or being diagnosed with gestational diabetes is considered a risk factor.

Given the stakes for the child as well as the mother, I do not believe, however, that we should require both overweight/obesity and previous macrosomia or gestational diabetes as criteria for testing.

Similarly, I believe that we should lower our diagnostic threshold for type 2 diabetes in patients who are pregnant. More than 60% of patients with gestational diabetes fall into the category of impaired glucose tolerance (fasting plasma glucose of 100–125 mg/dL). Today we are calling these patients gestational diabetics when they really should be called type 2 diabetics.

The recently completed National Institutes of Health-sponsored Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study and the study on gestational diabetes by the Maternal-Fetal Medicine Units Network (MFMU) used fasting plasma glucose levels of 105 mg/dL and 95 mg/dL, respectively, as thresholds for the exclusion of patients from the studies.

The HAPO study linked adverse pregnancy outcomes with glycemia levels that have traditionally been considered normal, and the MFMU study is yielding similar findings. However, given the studies' exclusion thresholds (which were set with ethical considerations in mind), we have disallowed ourselves the opportunity to firmly establish whether patients with impaired glucose tolerance should be considered type 2 diabetics.

Current diagnostic criteria for the population in general—by which a fasting blood glucose level (FBG) of 126 mg/dL indicates diabetes and an FBG of 100–125 mg/dL indicates impaired fasting glucose or prediabetes—were set several years ago when it became apparent that the previous diagnostic threshold of 140 mg/dL was too high. Studies showed clearly that complications relating to hyperglycemia—from retinopathy to nephropathy, neuropathy, and various micro- and macrovascular complications—occur in patients with FBG levels much lower than 140 mg/dL.

Recent research has shown, moreover, that long-term damage to the body may occur even in patients diagnosed with prediabetes. Investigators have reported, for instance, that approximately 10% of these patients have neuropathy and/or retinopathy.

When I see an FBG level of 100–125 mg/dL in a pregnant patient, even though this is by current standards considered “prediabetes” in the nonpregnant state, I consider this to be diabetes. This approach takes into account the fact that fasting plasma glucose levels during pregnancy are lower than actual values post pregnancy. It also takes into consideration something I have found in my discussions with patients: the observation that psychologically, these women are significantly more receptive to a serious approach to glycemic control if we're talking about diabetes rather than prediabetes or gestational diabetes.