Current management of diabetic pregnancy

New agents such as insulin analogs (mainly insulin lispro) and oral antidiabetic drugs (mainly glyburide) have profoundly altered the management of diabetes, producing obstetric outcomes comparable to those among the general population. Furthermore, in all types of diabetes, self-monitoring of blood glucose plus intensified drug therapy may help women achieve glycemic control and enhance perinatal outcomes at a lower cost than conventional management—and patients readily accept this approach.

This article describes the rationale for intensive treatment with these agents and other interventions to prevent both hypoglycemia and hyperglycemia.

Intensive therapy requires:

• memory-based self-monitoring of blood glucose, which empowers patients to take charge of glycemic control and provides feedback on the timing and dose of insulin administration,
  
• dietary regulation,
  
• strict criteria for initiation of pharmacologic therapy,
  
• multiple injections of insulin or its equivalent when diet alone is insufficient, and
  
• an interdisciplinary management team.
  

Two breakthrough studies in nonpregnant patients first showed the effectiveness of intensive therapy: the Diabetes Control and Complications Trial¹ and the United Kingdom Prospective Diabetes Study.^2,3 In the first, intensive therapy reduced the risk of retinopathy and lowered rates of microalbuminuria, albuminuria, and clinical neuropathy. In the second, intensive therapy substantially reduced the risk of microvascular complications.

Neither race nor ethnicity predicts treatment duration or success.^5-7

Blood glucose goals

Regardless of the treatment, the primary goal is always to achieve glycemic control, because it reduces the incidence of hypoglycemia, hyperglycemia, and ketosis. For type 1 and type 2 diabetes, glycemic control is important to prevent further deterioration of complications such as vasculopathy and nephropathy.

Goals of treatment are achieving the following blood glucose concentrations (in milligrams per deciliter):

• mean: 90 to 105
  
• fasting: 60 to 90
  
• preprandial: 80 to 95
  
• postprandial: less than 120
  

At each visit, the clinician evaluates these values and, when necessary, increases the dose of insulin or the oral agent to meet these goals.⁴

In the process, the clinician needs to anticipate how pregnancy will affect preexisting disease, and how diabetes will affect pregnancy outcomes, in patients with any of the 3 types of diabetes.

2 diet protocols

For all types of diabetes, the foundation is diet—specifically, using nutritional therapy to achieve and maintain a maternal blood glucose profile comparable to that of a nondiabetic woman.

Two approaches are recommended:

• reducing carbohydrate intake to 40% to 50% of total calories or
  
• limiting carbohydrate consumption to foods with a low glycemic index for approximately 60% of calories.
  

Only women who achieve targeted levels of glycemic control improve insulin secretion and sensitivity. Those who fail to achieve it may exhibit slightly improved sensitivity, but do not attain the same level of insulin response and sensitivity as non-diabetic women.^4,5

Calculating calories: Same for all

The daily caloric intake is based on the prepregnancy body mass index (BMI) and uses the same formula for all 3 types of diabetes^10,11:

• For a BMI less than 20 (underweight), daily caloric intake should be 35 to 38 kcal/kg.
  
• For a BMI of 20 to 25 (normal weight), the patient should consume 30 kcal/kg.
  
• For a BMI of 26 and higher (overweight, obese, morbidly obese), caloric intake should be 20 to 25 kcal/kg.
  

Calories per day are then calculated according to the patient’s weight during pregnancy and are adjusted throughout pregnancy as that weight increases.

In addition, the daily allotment of calories is divided into 3 main meals and 3 to 4 snacks, with adjustments for the patient’s time constraints, work schedule, and other individual factors.

To encourage compliance, the diet also should reflect the patient’s cultural preferences.

How do you know when diet fails?

Women with pregestational diabetes are usually already taking insulin or other pharmacologic agents by the time they conceive. There is no consensus or hard data on how long a woman who develops gestational diabetes mellitus should remain on a diet before starting drug treatment.

In a study evaluating the time required to achieve glycemic control with diet alone during a 4-week period, 70% of patients with fasting plasma below 95 mg/dL achieved established levels of glycemic control within 2 weeks with no substantial improvement thereafter.^8,9 In contrast, in patients with fasting plasma glucose of more than 95 mg/dL, most patients failed to achieve the desired level of glycemic control throughout the 4-week period.