What are the management strategies for a pregnant woman with pre-existing diabetes, including type 1 (T1D) and type 2 (T2D) diabetes, as well as gestational diabetes?

Management of Diabetes in Pregnancy

Insulin is the first-line and preferred pharmacologic agent for managing all types of diabetes during pregnancy (type 1, type 2, and gestational diabetes), as it does not cross the placenta and provides the safest option for both mother and fetus. 1, 2, 3

Preconception Care (For Pre-existing Diabetes)

Achieve A1C <6.5% (48 mmol/mol) before conception to minimize the risk of congenital anomalies including anencephaly, microcephaly, congenital heart disease, and caudal regression. 4, 2, 3

Essential Preconception Steps:

• Establish multidisciplinary care with an endocrinologist, maternal-fetal medicine specialist, registered dietitian nutritionist, and diabetes care and education specialist when available. 4

• Discontinue teratogenic medications immediately upon pregnancy planning or recognition: ACE inhibitors, angiotensin receptor blockers, and statins must be stopped as they cause fetotoxicity. 4, 1, 2, 3

• Obtain baseline testing: A1C, creatinine, urinary albumin-to-creatinine ratio, thyroid-stimulating hormone, and comprehensive dilated eye examination. 4

• Prescribe effective contraception and maintain use until glycemic targets are achieved. 4, 2

• Prescribe prenatal vitamins with at least 400 mg of folic acid. 4

Glycemic Targets During Pregnancy

Blood Glucose Targets:

• Fasting plasma glucose: <95 mg/dL (5.3 mmol/L) 4, 1, 2
• 1-hour postprandial: <140 mg/dL (7.8 mmol/L) 4, 1, 2
• 2-hour postprandial: <120 mg/dL (6.7 mmol/L) 4, 2

A1C Targets:

• Ideal target: <6% (42 mmol/mol) if achievable without significant hypoglycemia 4, 3
• Acceptable target: <7% (53 mmol/mol) if necessary to prevent hypoglycemia 4, 2

Note that A1C is physiologically lower in pregnancy due to increased red blood cell turnover, making it a less reliable marker than frequent glucose monitoring. 4

Glucose Monitoring Strategy

Implement fasting and postprandial self-monitoring of blood glucose in both gestational diabetes and preexisting diabetes. 4

• For women on basal-bolus insulin or pump therapy: Add preprandial testing to adjust rapid-acting insulin doses. 4

• Continuous glucose monitoring (CGM) can be used as an adjunct to self-monitoring and helps achieve A1C targets, reducing macrosomia and neonatal hypoglycemia in type 1 diabetes. 4

• Critical caveat: CGM metrics should NOT substitute for self-monitoring of blood glucose to achieve optimal pre- and postprandial targets, and estimated A1C/glucose management indicator calculations should NOT be used in pregnancy. 4

Medical Nutrition Therapy and Lifestyle Management

Begin with medical nutrition therapy, physical activity, and weight management before initiating pharmacologic therapy. 1

Nutritional Requirements:

• Minimum daily intake: 175g carbohydrate, 71g protein, 28g fiber 1
• Consistent carbohydrate intake to match insulin dosing and avoid glucose fluctuations 4, 2
• Referral to registered dietitian to establish food plan, insulin-to-carbohydrate ratio, and weight gain goals 4

Weight Gain Targets:

• Overweight (BMI 25-29.9): 15-25 lb (6.8-11.3 kg) 1, 3
• Obese (BMI ≥30): 10-20 lb (4.5-9.1 kg) 1, 3
• Never recommend weight loss during pregnancy due to increased risk of small-for-gestational-age infants 1

Insulin Management Protocol

Use multiple daily injections with basal-bolus regimen or insulin pump technology. 1

Insulin Dosing Dynamics:

• Early pregnancy (first trimester): Enhanced insulin sensitivity, lower glucose levels, and lower insulin requirements in type 1 diabetes 4

• Second and third trimesters: Insulin resistance increases exponentially with linear increases of approximately 5% per week starting around 16 weeks gestation 1

• Expect insulin requirements to double by the third trimester 1

• Type 2 diabetes often requires much higher insulin doses than type 1 diabetes, sometimes necessitating concentrated insulin formulations 3

Hypoglycemia Management:

• Educate patients and family members on hypoglycemia prevention, recognition, and treatment before, during, and after pregnancy, as counter-regulatory responses are altered 1
• Glucagon should be available to the patient and close contacts should be trained in its use 5

Alternative Pharmacologic Options

Metformin may be considered as adjunctive therapy to insulin in type 2 diabetes, but NOT as monotherapy, due to lack of long-term safety data. 1

This represents a nuanced area where insulin remains the gold standard, but metformin can augment therapy when insulin alone is insufficient. 1

Essential Adjunctive Therapies

Aspirin Prophylaxis:

Prescribe low-dose aspirin 100-150 mg daily starting at 12-16 weeks gestation to reduce preeclampsia risk, as diabetes significantly increases this risk. 1, 2, 3

Hypertension Management (if present):

• Target blood pressure: 110-135/85 mmHg to reduce risk of accelerated maternal hypertension while minimizing impaired fetal growth 2
• Never use ACE inhibitors or ARBs during pregnancy due to fetotoxicity 1, 2

Retinopathy Monitoring

Women with preexisting type 1 or type 2 diabetes require dilated eye examinations ideally before pregnancy or in the first trimester, then every trimester and for 1 year postpartum as indicated by retinopathy degree. 4, 2, 3

Critical pitfall: Rapid implementation of tight glycemic control in women with existing retinopathy can worsen retinopathy progression. 1, 2 Balance the need for euglycemia with gradual optimization when retinopathy is present.

Postpartum Management

Reduce insulin to 50% of end-pregnancy doses or 80% of pre-pregnancy doses immediately after delivery and monitor closely for hypoglycemia, especially during breastfeeding. 1

For gestational diabetes: Test for persistent diabetes or prediabetes at 4-12 weeks postpartum with a 75-g oral glucose tolerance test using nonpregnancy criteria. 2

Specialized Care Referral

Refer to a specialized center with multidisciplinary team due to the complexity of insulin management and high-risk nature of diabetic pregnancy. 4, 1, 3

Several studies demonstrate improved diabetes and pregnancy outcomes when care is delivered from preconception through pregnancy by a multidisciplinary group focused on improved glycemic control. 4

Common Pitfalls to Avoid

• Do not delay medication review: Every day of exposure to teratogenic medications (ACE inhibitors, ARBs, statins) increases fetal risk. 2

• Do not rely solely on A1C during pregnancy: Frequent self-monitoring of blood glucose with pre- and postprandial testing is essential. 4

• Do not use CGM as a substitute for fingerstick glucose monitoring: It is an adjunct only. 4

• Do not underestimate insulin requirements in type 2 diabetes: These patients often require higher doses than type 1 diabetes patients. 3

• Do not forget aspirin prophylaxis: Start at 12-16 weeks gestation in all women with diabetes. 1, 2, 3