What are the guidelines for managing diabetes in pregnancy?

Management of Diabetes in Pregnancy

Insulin is the preferred first-line medication for managing diabetes during pregnancy, with strict glycemic targets of fasting glucose <95 mg/dL and 1-hour postprandial <140 mg/dL (or 2-hour postprandial <120 mg/dL), and an A1C target <6% if achievable without significant hypoglycemia. 1, 2

Preconception Planning

Women with preexisting diabetes should achieve optimal glycemic control before conception to reduce risks of congenital malformations and spontaneous abortion:

• Target A1C <6.5% before conception to minimize risk of diabetic embryopathy, including anencephaly, microcephaly, and congenital heart disease 1
• Discontinue teratogenic medications including ACE inhibitors and statins 1
• Initiate folic acid supplementation at 400 mg daily 1
• Complete comprehensive screening: thyroid function, renal function (creatinine and urine albumin-to-creatinine ratio), ophthalmologic examination, and cardiovascular assessment 1
• Establish effective contraception until glycemic targets are achieved 1

Glycemic Targets During Pregnancy

Blood Glucose Monitoring Targets

For gestational diabetes mellitus (GDM):

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

For preexisting type 1 or type 2 diabetes:

• Fasting: 70-95 mg/dL (3.9-5.3 mmol/L) 1
• 1-hour postprandial: 110-140 mg/dL (6.1-7.8 mmol/L) 1
• 2-hour postprandial: 100-120 mg/dL (5.6-6.7 mmol/L) 1

A1C Targets

• Primary target: <6% (42 mmol/mol) if achievable without significant hypoglycemia 1
• Alternative target: <7% (53 mmol/mol) if necessary to prevent hypoglycemia 1
• Monitor A1C monthly due to increased red blood cell turnover during pregnancy 1
• Critical caveat: A1C is a secondary measure; self-monitoring of blood glucose is the primary tool for glycemic management 1

Monitoring Strategy

Blood Glucose Monitoring

Postprandial monitoring is superior to preprandial monitoring alone for achieving glycemic control and reducing neonatal complications 3:

• Check fasting glucose daily 1
• Check 1-hour postprandial glucose after each meal (preferred over 2-hour postprandial) 3
• Women using basal-bolus insulin or insulin pumps should also check preprandial glucose to adjust rapid-acting insulin doses 1
• Postprandial monitoring reduces macrosomia (12% vs 42%), neonatal hypoglycemia (3% vs 21%), and cesarean delivery rates (12% vs 36%) compared to preprandial monitoring 3

Continuous Glucose Monitoring (CGM)

• CGM should be used as an adjunct to, not a replacement for, self-monitoring of blood glucose 1
• CGM reduces large-for-gestational-age births, neonatal hypoglycemia, and length of hospital stay in type 1 diabetes 1
• Do not use estimated A1C or glucose management indicator calculations from CGM devices during pregnancy 1

Insulin Management

Insulin as First-Line Therapy

Insulin is mandatory for type 1 diabetes and preferred for type 2 diabetes and GDM when lifestyle modifications fail to achieve targets 1, 2, 4:

• Insulin does not cross the placenta and is the safest pharmacologic option 2
• 70-85% of women with GDM can achieve targets with lifestyle modification alone; the remainder require insulin 1

Insulin Physiology During Pregnancy

Understanding physiologic changes is essential for appropriate insulin dosing 1, 2:

• First trimester: Enhanced insulin sensitivity; insulin requirements often decrease; increased hypoglycemia risk 1, 2
• Second trimester (starting ~16 weeks): Insulin resistance increases exponentially; requirements increase ~5% per week 1
• Third trimester: Total daily insulin dose typically doubles compared to prepregnancy requirements 1, 2
• Late third trimester: Insulin requirements plateau; rapid reduction may indicate placental insufficiency requiring immediate evaluation 1, 2

Insulin Regimen

• Use physiologic basal-bolus regimens with rapid-acting insulin for meals and long-acting insulin for basal coverage 1, 4
• Greater proportion of total daily dose should be prandial insulin rather than basal insulin 1
• Both multiple daily injections and continuous subcutaneous insulin infusion (insulin pump) are appropriate 2
• Adjust insulin doses weekly or biweekly during second trimester to match increasing insulin resistance 1

Insulin Types in Pregnancy

• Most insulins are pregnancy category B 1
• Insulin glargine and glulisine are labeled category C but are commonly used 1

Management of Gestational Diabetes Mellitus

Initial Management

• Start with medical nutrition therapy, exercise, and glucose monitoring 1
• Initiate insulin if glucose targets are not achieved with lifestyle modifications within 1-2 weeks 1
• Do not rely on initial fasting glucose to predict insulin need; all women with GDM require self-monitoring regardless of initial fasting glucose level 5

Treatment Escalation

• If fasting glucose >95 mg/dL on multiple occasions or postprandial targets consistently exceeded, initiate insulin 1, 5
• Treatment improves perinatal outcomes including reduced macrosomia and birth complications 1

Special Considerations

Nutrition and Lifestyle

• Consistent carbohydrate intake is essential to match insulin dosing and prevent glucose fluctuations 2
• Establish individualized meal plans with appropriate insulin-to-carbohydrate ratios 1
• Regular moderate exercise is recommended 1

Hypoglycemia Prevention

• Education on hypoglycemia recognition, prevention, and treatment is mandatory for all pregnant women with diabetes and their family members 2
• Balance glycemic targets against hypoglycemia risk, particularly in women with hypoglycemia unawareness 1

Complication Screening

• Comprehensive ophthalmologic examination at baseline and as needed throughout pregnancy 1
• Monitor for progression of diabetic retinopathy 1
• Screen for preeclampsia risk, which is increased with diabetes 1

Postpartum Management

• Insulin requirements decrease dramatically immediately after placental delivery 2
• Close monitoring and rapid insulin dose reduction are necessary in the immediate postpartum period to prevent hypoglycemia 2
• Women with GDM have increased risk of developing type 2 diabetes and require postpartum screening 1