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How Type 2 Diabetes Complicates Pregnancy


 

With the incidence of obesity rising in the United States and Europe, the rate of type 2 diabetes is increasing significantly as well. In 2000, investigators reported a 33% increase from 1990 to 1998 in the prevalence of type 2 diabetes, and a 76% prevalence increase in individuals aged 30–39 years (Diab. Care 2000:23:1278–83). Others have estimated that the majority of pregestational pregnant diabetic women (80%–90%) are type 2.

The rates of obesity and type 2 diabetes have risen further since 2000, so much so that the current pandemic—now often referred to “diabesity”—has implications that are more urgent than ever for obstetrics and for our goal of optimizing outcomes for women and their newborns. Today it is estimated that 8%–15% of pregnant women have type 2 diabetes, and if current trends continue, it will soon be higher.

Unless we take a more aggressive and intensive approach to identification and management—unless we aim for primary prevention of hyperglycemia-related complications to the greatest degree possible—a significant number of our pregnant patients will face complications and adverse perinatal outcomes associated with type 2 diabetes.

We have to focus on the care of these women with the same diligence that has been applied to pregnant and nonpregnant women with type 1 diabetes. For one, we must be more proactive in promoting preconception care, and in cases in which that doesn't happen, we must act early to identify potentially harmful levels of glycemia.

We must then strive for as much glycemic control as possible, because various levels of improvement can prevent different anomalies and complications.

Perinatal Outcomes

Compared with type 1 diabetes, there are relatively few data on the effects of type 2 diabetes on pregnancy outcome. Still, evidence is mounting that the abnormal maternal glycemic profiles characterizing type 2 diabetes are associated with adverse perinatal outcome, and that improvement in glycemic control results in better perinatal outcomes.

Investigators have consistently reported significantly higher rates of perinatal morbidity and mortality in women with type 2 diabetes than in the general population, and most studies report a prevalence of congenital anomalies in the offspring of women with type 2 diabetes that is several times higher than the rate found in the general population and similar to the prevalence of congenital anomalies associated with type 1 diabetes. (The rate of congenital abnormalities contributes significantly, of course, to overall perinatal mortality.) Other studies suggest that the rate of congenital anomalies in the children of women with type 2 diabetes is twice as high as the rate reported with type 1 diabetes.

Fetal macrosomia is another major problem. Most studies report fourfold to fivefold higher rates of macrosomia in infants of mothers with type 2 diabetes. Metabolic and respiratory complications also occur. More specifically, the perinatal mortality in women with type 2 diabetes has varied from approximately 3.7% in a study done in New Zealand to 18% in research conducted in Canada, with an overall mean of 7.6% in the 14 studies conducted since 2000.

The rate of major anomalies in type 2 diabetic women has ranged from 3% in South Africa to 12.3% in the United Kingdom with an overall mean of 8% in the 17 studies conducted since 2000. The rate of anomalies in the general population, as reported in only 6 of the 17 studies, has ranged from 1.6% to 3.1%.

The rate of large-for-gestational-age (LGA) infants in studies addressing type 2 diabetes and published between 1970 and 1980 was 33% (a range of 28%–40%). The rate reported since 2000 in published studies is 39% (a range of 30%–45%). The rate of cesarean section since 2000 is 62% (J. Mater. Fetal Med. 2008:21;181–9).

Unfortunately, in the past 4–5 decades, we have not improved the care of pregnant patients with type 2 diabetes. There has been no significant change in perinatal outcomes. Analyses of anomaly rates, for instance, show no real change since the 1970s. We have to ask, therefore, what are we really doing for these patients?

Part of the problem is that patients are diagnosed too late. The majority of women with type 2 diabetes is seen for the first prenatal visit during or after organogenesis occurs. We talk with patients about organogenesis occurring during the first trimester, but most anomalies actually occur in the first 4–5 weeks of pregnancy.

Only a small percentage of type 2 patients (5%–24%) receive preconception care, a shortcoming driven partly by the fact that 50%–60% of pregnancies are unplanned and partly by our own failures in the public health and preventive arena. Moreover, testing for gestational diabetes, which often uncovers type 2 diabetes, does not occur until about midpregnancy.

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