Rationale:

• Calorie restriction may reduce hyperglycemia in obese diabetic pregnant patients.
• Carbohydrate restriction may decrease maternal glucose levels and improve maternal and fetal outcomes in diabetic pregnant patients.
• Moderate exercise may reduce glucose levels in diabetic pregnant patients.
• Maternal hyperglycemia is associated with fetal malformations and macrosomia.

Evidence:

• A small randomized, controlled trial of obese women with gestational diabetes showed a reduction in 24-hour mean glucoses from 121 mg/dL to 97.3 mg/dL in women assigned to a 1,200 calories per day diet as compared with women on a 2,400 calories per day diet; however, maternal ketonuria of unknown clinical significance was also seen (25; 26).
• In a controlled trial, calorie restriction of 33% and 50% in obese women with gestational diabetes decreased maternal glucose levels by 10% to 20% and reduced triglyceride levels when compared with insulin therapy (27).
• In a 12-week controlled trial of obese pregnant women, half of whom had previous gestational diabetes, all of the women had higher triglycerides while on a 55% carbohydrate diet than while on a 40% carbohydrate diet and comparable weight loss (28).
• A small randomized, controlled trial demonstrated increased cardiac fitness in women with gestational diabetes who exercised 30 minutes, 3 to 4 days per week, and achieved 70% of estimated maximal heart rate. No complications were seen (29).
• A small randomized, controlled trial showed reduced glucose levels in women with gestational diabetes who performed upper-extremity aerobic exercise (30).
• A small randomized study showed a decreased need for insulin in overweight women with gestational diabetes assigned to resistance exercise (31).
• Two cohort studies have prospectively examined the role of exposure to diabetes in utero on childhood growth, later obesity, and risk for type 2 diabetes in the offspring: the Pima Indian Study (43) and the Diabetes in Pregnancy Study at Northwestern University in Chicago (44).
• The excess growth experienced by offspring of diabetic mothers is not due to genetic factors alone but is also the direct consequence of exposure to maternal altered intrauterine environment as shown in a study of 58 siblings (45). In another study of 150 HNF-1-α mutation carriers in utero, maternal diabetes resulted in diagnoses of diabetes in the carriers at a younger age (46).
• In utero exposure to diabetes confers risks for the development of cardiovascular disease later in life that are independent of adiposity and may be in addition to genetic predisposition to diabetes as shown in a study comparing 61 children born to diabetic mothers as compared to 57 control children of nondiabetic mothers (47), and in a study of 42 Pima Indian children born to diabetic mothers in whom most had higher levels of HbA1c and systolic blood pressure and lower levels of HDL independent of age, gender, or percent body fat (48).

Comments:

• Little data exist concerning women with pregestational diabetes and diet or exercise. Consensus opinion on patients with diabetes mellitus stresses the importance of diet and exercise for weight and glycemic control.