What is the best way to manage pre-existing type 2 diabetes in a pregnant woman?

Management of Pre-existing Type 2 Diabetes During Pregnancy

Insulin is the mandatory first-line therapy for managing pre-existing type 2 diabetes during pregnancy, combined with medical nutrition therapy and intensive glucose monitoring to achieve strict glycemic targets that prevent maternal and fetal complications. 1, 2

Preconception Planning and Optimization

Before pregnancy occurs, achieve optimal glycemic control to prevent congenital malformations:

• **Target A1C <6.5% before conception** to minimize the risk of major birth defects, which can be as high as 20-25% with A1C >10% 1, 3
• Discontinue teratogenic medications including ACE inhibitors, angiotensin receptor blockers, and statins immediately upon conception planning 1
• Screen for and manage diabetes complications: comprehensive ophthalmologic exam for retinopathy, serum creatinine and urine albumin-to-creatinine ratio for nephropathy, ECG if age ≥35 years or cardiac risk factors present, comprehensive foot exam, and TSH 1
• Implement reliable contraception until glycemic targets are achieved, as the risk of unplanned pregnancy outweighs any contraceptive risk 1

Glycemic Targets During Pregnancy

Achieve the following strict glucose targets, which are more stringent than non-pregnant goals:

• Fasting glucose <95 mg/dL (5.3 mmol/L) 1
• One-hour postprandial <140 mg/dL (7.8 mmol/L) 1
• Two-hour postprandial <120 mg/dL (6.7 mmol/L) 1
• A1C target <6% (42 mmol/mol) if achievable without significant hypoglycemia, but may be relaxed to <7% (53 mmol/mol) if necessary to prevent hypoglycemia 1

Insulin Management Strategy

Insulin Initiation and Dosing

• Insulin is mandatory for all women with pre-existing type 2 diabetes during pregnancy as it does not cross the placenta and is the safest option 2, 3
• Both multiple daily injections and continuous subcutaneous insulin infusion (pump therapy) are appropriate delivery strategies, with neither proven superior 1, 2
• Women with type 2 diabetes often require much higher insulin doses than those with type 1 diabetes due to insulin resistance, sometimes necessitating concentrated insulin formulations 1

Physiologic Insulin Requirements Throughout Pregnancy

• Early pregnancy (first trimester): Enhanced insulin sensitivity leads to lower insulin requirements and increased hypoglycemia risk 1, 2
• Second and third trimesters: Insulin resistance increases exponentially, with requirements rising to 2-3 times pre-pregnancy levels by approximately 16 weeks 1, 2
• Immediate postpartum: Insulin requirements drop dramatically to approximately 34% lower than pre-pregnancy levels with placental delivery 1, 4

Insulin Types and Safety

According to FDA labeling, both insulin detemir and insulin lispro have been studied in pregnancy:

• Insulin detemir shows no clear evidence of maternal or fetal risk in clinical trials with pregnant women with type 1 diabetes 5
• Insulin lispro has published data showing no association with major birth defects, miscarriage, or adverse maternal/fetal outcomes when used during pregnancy 6
• Rapid-acting insulin analogs (lispro, aspart) improve postprandial glucose control and are considered safe and effective in pregnancy 7

Glucose Monitoring Protocol

• Perform both fasting and postprandial blood glucose monitoring to achieve metabolic control 1, 2
• Preprandial testing is essential when using insulin pumps or basal-bolus therapy to adjust rapid-acting insulin doses 1, 2
• Continuous glucose monitoring (CGM) improves glycemic control and reduces hypoglycemia risk when used in addition to self-monitoring of blood glucose, but CGM metrics should not substitute for achieving optimal pre- and postprandial targets 1, 2

Medical Nutrition Therapy

• Refer to a registered dietitian nutritionist to establish a food plan, insulin-to-carbohydrate ratio, and weight gain goals 1
• Consume consistent amounts of carbohydrates to match insulin dosing and avoid hyperglycemia or hypoglycemia 1
• Emphasize nutrient-dense whole foods including fruits, vegetables, legumes, whole grains, and healthy fats with omega-3 fatty acids 1
• Avoid severely restrictive diets including ketogenic diets (lack carbohydrates), Paleo diets (dairy restriction), and diets with excess saturated fats 1
• Limit processed foods, fatty red meat, and sweetened foods/beverages 1

Weight Gain Targets

• Women with overweight: 15-25 pounds total weight gain 1
• Women with obesity: 10-20 pounds total weight gain 1

Prevention of Complications

Preeclampsia Prevention

• Prescribe low-dose aspirin 100-150 mg/day starting at 12-16 weeks gestation to lower preeclampsia risk (81 mg is insufficient; >100 mg required for efficacy) 1

Hypertension Management

• Target blood pressure 110-135/85 mmHg to reduce accelerated maternal hypertension while minimizing impaired fetal growth 1
• Avoid ACE inhibitors and angiotensin receptor blockers throughout pregnancy 1

Hypoglycemia Prevention

• Provide education on hypoglycemia prevention, recognition, and treatment to the patient and family members 1, 2
• Prescribe glucagon and train close contacts in its use, as severe hypoglycemia rates increase during pregnancy 3
• Be particularly vigilant in the first trimester when insulin sensitivity is enhanced 1, 2

Diabetic Ketoacidosis (DKA) Prevention

• Women with type 2 diabetes are at risk for DKA at lower glucose levels than in the non-pregnant state 1
• Never interrupt basal insulin therapy due to high risk of ketoacidosis 4
• Women requiring DKA treatment often need 10% dextrose with insulin infusion to meet higher carbohydrate demands of the placenta and fetus 1

Labor and Delivery Management

• Switch from subcutaneous insulin to intravenous insulin infusion during active labor 4
• Administer 10% glucose infusion alongside insulin to prevent maternal hypoglycemia and ketosis during labor's increased energy demands 4
• Continue IV insulin-glucose protocol through delivery 4

Immediate Postpartum Management

• Reduce insulin immediately after placental delivery to either 80% of pre-pregnancy doses or 50% of end-pregnancy doses 4
• Target blood glucose 110-160 mg/dL (6-8.8 mmol/L) after delivery 4
• Monitor closely for hypoglycemia, especially during breastfeeding and with irregular sleep patterns 1, 4

Breastfeeding Support

• Support all women with diabetes in breastfeeding attempts, as it provides immediate nutritional and immunological benefits to the baby and may confer longer-term metabolic benefits to both mother and offspring 1
• Exogenous insulin products transfer into human milk but no adverse reactions in breastfed infants have been reported 5, 6

Critical Pitfalls to Avoid

• Never discontinue basal insulin in type 2 diabetes patients, as this can rapidly lead to ketoacidosis even with moderately elevated glucose 4
• Avoid excessive insulin dosing in the immediate postpartum period, which can cause severe hypoglycemia as requirements drop dramatically 4
• Do not use metformin in women with hypertension, preeclampsia, or at risk for intrauterine growth restriction due to potential for growth restriction or acidosis 1
• Recognize that pregnancy loss appears more prevalent in the third trimester in women with type 2 diabetes compared to first trimester losses in type 1 diabetes 1